|
|
|
|
|
|
|
||||
| Home Help Feedback Subscriptions Archive Search Table of Contents | ||||
First published online 18 October 2006
doi: 10.1242/dev.02609
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Centro de Biología Molecular Severo Ochoa (C.S.I.C.-U.A.M.), Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain.
* Author for correspondence (e-mail: esherrero{at}cbm.uam.es)
Accepted 4 September 2006
 |
SUMMARY |
|---|
 TOP SUMMARY INTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
Key words: Hox, Ultrabithorax, decapentaplegic, Size control, Imaginal disc, Drosophila
|
INTRODUCTION |
|---|
|
TOPSUMMARYINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
).
In Drosophila, mutations in these genes frequently transform one
structure into another keeping the coordinates provided by underlying
positional information, established in part by the activity of signaling
pathways. Mutations in the Ultrabithorax (Ubx) Hox gene
illustrate this assertion. Wings and halteres are homologous structures
located in the second and third thoracic segments, respectively. These
appendages greatly differ in size and pattern, and derive from imaginal discs,
the wing and haltere discs, which also differ in size but bear a similar
morphology. Ubx, which is expressed in the haltere disc but not in
the wing disc, determines the difference between these two structures:
mutations in Ubx transform halteres into wings whereas Ubx
ectopic expression changes wings into halteres
(Lewis, 1963;
Lewis, 1978;
Cabrera et al., 1985;
White and Akam, 1985;
White and Wilcox, 1985). These
transformations respect positional cues
(Morata and García-Bellido,
1976) dictated by signaling pathways.
In Drosophila, one of the best-studied signaling pathways is that
of the decapentaplegic (dpp) gene (homologous to the
TGF-ß in vertebrates). This pathway has been analyzed extensively in
pattern formation of the imaginal discs, particularly the wing disc (reviewed
by Tabata, 2001). This disc is
subdivided early in development into an anterior (A) and a posterior (P)
compartment (García-Bellido et al.,
1973). The protein encoded by the hedgehog (hh)
gene, synthesized in the posterior compartment, activates dpp
transcription in anterior cells close to the anteroposterior (A/P) border
(Posakony et al., 1991;
Basler and Struhl, 1994;
Capdevila and Guerrero, 1994;
Tabata and Kornberg, 1994).
The Dpp ligand diffuses into both A and P compartments, generating a gradient
of protein concentration (Entchev et al.,
2000; Teleman and Cohen,
2000). Dpp behaves as a morphogen, translating the protein
concentration gradient into the restricted and overlapping expression of genes
like spalt (sal) and optomotor-blind (omb)
(Lecuit et al., 1996;
Nellen et al., 1996). Among
these, the sal gene is repressed by Ubx in the haltere pouch
(Weatherbee et al., 1998;
Barrio et al., 1999;
Galant et al., 2002),
indicating that the outcome of Dpp signaling is modified by Ubx in
the haltere disc.
Dpp activity can be monitored with an antibody that recognizes the
phosphorylated form of Mothers against dpp (Mad)
(Persson et al., 1998;
Tanimoto et al., 2000), a
receptor-regulated Smad that transduces the dpp signal
(Newfeld et al., 1997). The
analysis of this and other Dpp pathway elements has revealed their different
contribution to the formation of the Dpp ligand and activity gradients. Thus,
the expression in the wing disc of one type I Dpp receptor, thick
veins (tkv), is not uniform, and this unequal distribution
modulates Dpp signaling along the A/P axis (Haerry et al., 1998;
Lecuit and Cohen, 1998;
Tanimoto et al., 2000).
Similarly, the spread and activity of Dpp depends on the presence of
cell-surface molecules like those encoded by the division abnormally
delayed (dally) and dally-like protein (dlp)
genes (Jackson et al., 1997;
Nakato et al., 1995;
Fujise et al., 2003;
Belenkaya et al., 2004). All
these elements establish the fine tuning of Dpp activity, which is crucial in
determining the form and size of Drosophila wings
(Spencer et al., 1982;
Capdevila and Guerrero, 1994;
Zecca et al., 1995;
Lecuit et al., 1996;
Nellen et al., 1996;
Tsuneizumi et al., 1997;
Haerry et al., 1998; Lecuit and Cohen,
1998; Campbell and Tomlinson,
1999; Jazwinska et al.,
1999; Minami et al.,
1999;
Martín-Castellanos and Edgar,
2002; Martín et al.,
2004). Therefore, the shape and size of adult derivatives can be
established by adjusting the Dpp input in imaginal cells.
Ubx mutations increase the size of the halteres, transforming them
into wings (Lewis, 1963)
whereas dpp mutations reduce the size of the halteres
(Spencer et al., 1982).
Changes in the Dpp pathway affect wing size (reviewed by
Day and Lawrence, 2000), and
recent evidence indicates that cell proliferation in the wing disc is induced
by reading different Dpp activity levels
(Rogulja and Irvine, 2005).
Although the Ubx and dpp effects (in halteres and wings)
could be unrelated, the homologous nature of both appendages suggests that
Ubx may fix haltere size by modifying the Dpp pathway. We have
explored this idea and compared Dpp distribution and activity in the wing and
haltere discs. We show that Ubx downregulates dpp
expression, alters Dpp activity and reduces Dpp spread, and that the latter is
achieved mainly by controlling the expression of tkv and
dally. Our results have implications in the way Ubx
establishes the different size of halteres and wings.
|
MATERIALS AND METHODS |
|---|
|
TOPSUMMARYINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
).
Ubx6.28 is a null allele of Ubx
(Beachy et al., 1985), the
TM2 balancer carries the Ubx130 null mutation
(Lewis, 1952), and the
Df109 deletion eliminates the Ubx gene
(Lewis, 1978). The
bx3 and pbx mutations eliminate Ubx
expression in the anterior and posterior compartments of the haltere disc,
respectively, transforming them into the corresponding ones of the wing disc
(Lewis, 1963;
García-Bellido et al.,
1973; Cabrera et al.,
1985; White and Wilcox,
1985). The CbxTwt mutation ectopically
expresses Ubx in the wing disc
(Bender et al., 1983).
DfC1-h1 (Szidonya and Reuter,
1988) and Df tkv2
(Szidonya and Reuter, 1988;
Terracol and Lengyel, 1994)
are deficiencies that uncover the tkv gene. The following reporter
insertions or constructs were used: dpp-lacZBS3.0
(Blackman et al., 1991),
dpp-lacZ10638 (Twombly
et al., 1996), hh-lacZ
(Lee et al., 1992)
dally-lacZ (Nakato et
al., 1995), tkv-lacZ
(Tanimoto et al., 2000),
mtv-lacZ (Funakoshi et
al., 2001) and omb-lacZ
(Grimm and Pflugfelder, 1996).
The Gal4/UAS method (Brand and Perrimon,
1993) was used with the following Gal4 lines and UAS constructs:
dpp-Gal4 (Morimura et al.,
1996), en-Gal4
(Tabata et al., 1995),
ptc-Gal4 (Hinz et al.,
1994), ap-Gal4
(Calleja et al., 1996),
MS1096-Gal4 (Capdevila and
Guerrero, 1994), UAS-dpp
(Capdevila and Guerrero,
1994), UAS-Dpp-GFP (Entchev et
al., 2000), UAS-tkv
(Lecuit and Cohen, 1998),
UAS-tkvQ253D (Nellen
et al., 1996), UAS-tkvDN (Haerry et al.,
1998), UAS-dally (Tsuda et al.,
1999), UAS-mtv (T. Tabata, unpublished), UAS-Ubx
(Castelli-Gair et al., 1994),
UAS-dsRNA>Ubx (Monier et al.,
2005) and UAS-GFP (Ito et al.,
1997). The tub- Gal80ts/Gal4 system
(McGuire et al., 2003) was
used to temporally control the induction of transgenes with the Gal4/UAS
method. To this aim, larvae were transferred from 17°C to 29°C during
the second or third larval instars.
Clonal analysis
We used the FLP/FRT system (Xu and
Rubin, 1993) to induce Ubx mutant clones in the haltere
disc with the FRT82B Ubx6.28 chromosome
(Weatherbee et al., 1998), the
MARCM method (Lee and Luo,
1999) to induce clones that lose Ubx and activate
tkv in the haltere disc, and the combination of FLP/FRT and Gal4/UAS
methods (Pignoni and Zipursky,
1997; Ito et al.,
1997) to induce Ubx-expressing clones in the wing disc;
in all the cases the clones were induced during the larval period. The
genotypes of the larvae where the clones were induced are as follows.
Ubx- clones: y hs-flp122; FRT82B Ubx6.28/FRT82B Ubi-GFP, y hs-flp122; FRT82B Ubx6.28 hh-lacZ/FRT82B Ubi-GFP and ptc-Gal4/UAS-flp; FRT82B Ubi-GFP/FRT82B Ubx6.28
Ubx- clones, dpp-lac-Z: y hs-flp122; dpp-lacZBS3.0/+; FRT82B Ubx6.28/FRT82B Ubi-GFP
Ubx- clones, omb-lac-Z: y hs-flp122/omb-lacZ; FRT82B Ubx6.28/FRT82B Ubi-GFP
Ubx- clones, tkv-lacZ: y hs-flp122; tkv-lacZ/+; FRT82B Ubx6.28/FRT82B Ubi-GFP
Ubx- clones, mtv-lacZ: y hs-flp122; mtv-lacZ/+; FRT82B Ubx6.28/FRT82B Ubi-GFP
Ubx- tkv+ clones, omb-lacZ: y hs-flp122 tub-Gal4 UAS-GFP/omb-lacZ; UAS-tkv FRT82B Ubx6.28/FRT82B tub-Gal80
Ubx+ clones, dally-lacZ: y hs-flp122; act5C>y+>Gal4 UAS-GFP/UAS-Ubx; dally-lacZ/+.
In situ hybridization
In situ hybridization was performed as previously described
(Azpiazu and Frasch, 1993;
Wolff, 2000). The RNA
dpp probe was synthesized from a BS-dpp plasmid containing a
dpp cDNA (kindly provided by A. Macías), digested with KpnI
and transcribed with the T3 polymerase.
Immunohistochemistry
Immunohistochemistry was carried out as previously described
(Sánchez-Herrero, 1991;
Estrada and Sánchez-Herrero,
2001). The antibodies used were: mouse and rabbit
anti-ß-galactosidase (Cappel), mouse Mab4D9 anti-En
(Patel et al., 1989), rat
anti-Tkv (Teleman and Cohen,
2000), rabbit anti-P-Mad
(Tanimoto et al., 2000;
Persson et al., 1998) [a gift
of F. A. Martín and G. Morata, Centro de Biologia Molecular, Severo
Ochoa (C.S.I.C.-U.A.M.), Madrid, Spain], and mouse anti-Ubx
(White and Wilcox, 1984).
Secondary antibodies were coupled to Red-X, Texas Red, FITC and Cy5
fluorochromes (Jackson ImmunoResearch).
Adult cuticle analysis
Flies were kept in a mixture of ethanol:glycerol (3:1) until needed. Flies
were then macerated in 10% KOH at 60°C for 10 minutes, dissected, washed
with water, dehydrated with ethanol and finally mounted in Euparal for
inspection under a compound microscope.
Measurements in the imaginal discs
We calculated the width in haltere and wing pouches with the Measure Tool
of Adobe Photoshop 8.0 using the position of the dorsoventral boundary as a
reference line for these measurements.
The intensity of the Dpp-GFP dots was calculated with the MetaMorph Offline program. The final profiles of the intensities were obtained following the same procedure in bx3/MKRS wing and haltere discs and in bx3/TM2 haltere discs. We first calculated the average value, along the A/P axis, of the GFP intensity in three different sections of a disc. This gives a mean value for the disc. We repeated this in three different discs of each type, thereby obtaining three mean values in each case. The final profile for either wing, haltere or bx3/TM2 haltere discs was obtained by plotting along the A/P axis the average of those three mean values obtained for each type of disc. The fixation and staining for all the discs was done simultaneously and under the same conditions. All pictures were processed under identical conditions.
|
RESULTS |
|---|
|
TOPSUMMARYINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
)
(Fig. 1A). To better define
this expression we have used a dpp-lacZ reporter construct
and a dpp-lacZ insertion that mimic dpp
transcription in the imaginal discs
(Blackman et al., 1991;
Twombly et al., 1996;
Weatherbee et al., 1998). Both
give comparable results. In the wing pouch, the dpp-lacZ stripe
(dpp-lacZ10638) is about 8.1 cells wide
(n=16) whereas in the haltere pouch it is about 6.0 cells
(n=13; Fig.
1B-D'). Anterior Ubx mitotic recombination clones
abutting the A/P boundary increase both the intensity of the signal and the
width of the stripe (Fig.
1E,E'). To characterize how Ubx regulates
dpp signal in A and P compartments, we used the bithorax
(bx) and postbithorax (pbx) mutations (see
Materials and methods). In bx (bx3/TM2)
haltere discs, the width of the dpp-lacZ stripe is about 7.9 cells
(n=10; Fig.
1F,F') approaching that of the wing disc (8.1 cells),
whereas in pbx (pbx/TM2) haltere discs the average
width is 6.4 cells (n=8; Fig.
1G,G'), slightly higher than in the wild type (6 cells).
Therefore, the reduction in dpp transcription by Ubx depends
mainly on the Ubx activity in the anterior compartment of the haltere
disc.
Ubx controls the response to the dpp signal by retarding Dpp diffusion
To study whether Ubx governs the response to Dpp signaling, we
monitored the expression of omb, a target of the dpp
pathway, with an omb-lacZ insertion
(Grimm and Pflugfelder, 1996;
Lecuit et al., 1996;
Nellen et al., 1996). As in
the wing disc (Fig.
2A-A''), omb is expressed in both compartments of
the haltere pouch (Weatherbee et al.,
1998) (Fig.
2B-B''). In strong bx and pbx mutants
omb expression in A and P compartments of the haltere disc resembles
that of the corresponding compartments of the wing disc
(Fig. 2C-D''). Because in
bx mutants the dpp expression is like that of the wing disc
(Fig. 1F) but omb
expression in the P compartment is not
(Fig. 2C), and because in
pbx mutants dpp transcription in the haltere disc is only
slightly increased (Fig. 1G),
but omb signal is clearly extended
(Fig. 2D), Ubx
probably regulates the response to the Dpp signal. This conclusion is
reinforced by the analysis of omb transcription in Ubx
mutant clones: clones located outside the omb expression domain do
not activate omb transcription. When the clones encompass the border
of omb expression, the omb signal is extended further
anteriorly or posteriorly. Notably, in some cases there is ectopic
omb transcription outside the clone, indicating a non-cell-autonomous
effect of Ubx loss on omb expression
(Fig. 2E-F''). Taken
together, these results indicate that Ubx represses omb
activation in cells that receive a low amount of Dpp, but that a certain level
of Dpp is required to activate omb even in the absence of
Ubx.
|
;
Teleman and Cohen, 2000). The
GFP signal is more restricted in the haltere disc than in the wing disc (not
shown). We aimed to quantify these differences and, for that, we used the
ptc-Gal4 driver to drive Dpp-GFP expression because the
dpp-Gal4 driver directs more irregular and variable expression in the
haltere disc. The extension of Dpp-GFP expression is higher in
tub-gal80ts/ptc-Gal4; UAS-Dpp-GFP
bx3/MKRS wing discs than in haltere discs of the
same genotype (Fig. 3A,B). In
tub-gal80ts/ptc-Gal4; UAS-Dpp-GFP
bx3/TM2 haltere discs the expression levels and
anterior extent of the fusion protein are very similar to those of the wing
disc, but the spread in the posterior compartment is only slightly increased
with respect to the wild type (Fig.
3C). A summary of the data is shown in
Fig. 3D. This shows that the
Dpp-GFP signal falls to background levels more abruptly in haltere discs than
in the wing discs or in the anterior compartment of bx haltere discs.
This difference is more evident in medial regions of both compartments: in
these regions there is a graded decrease of the Dpp-GFP signal in the wing
disc, whereas the distribution profile is flat in the haltere disc. A plot of
the GFP-Dpp dot distribution in three different sections of a single wing or
haltere disc is shown in Fig. S1 in the supplementary material. These results,
together with our previous observations, strongly suggest that Ubx
counteracts the spread of Dpp in the haltere pouch.
High levels of tkv in the haltere disc are induced by Ubx through regulation of mtv expression and dpp activity
We have just shown that Ubx reduces Dpp diffusion in the haltere
disc, thus limiting omb expression. To draw a general conclusion
about how Ubx regulates Dpp signaling we looked at the distribution
of the phosphorylated form of Mad (P-Mad), a major readout of Dpp activity
(Tanimoto et al., 2000). The
P-Mad signal in the haltere pouch is narrower than the signal in the wing
pouch, confined almost exclusively to the anterior compartment and not reduced
in AB cells (Fig. 4A-C').
Hence, and also in contrast with the wing disc
(Fig. 4D-D''), high levels
of both Hh and Dpp signaling coincide in these cells
(Fig. 4E-E''). The low Dpp
signaling in central cells of the wing disc is due to the reduced expression
of tkv, which is more strongly expressed peripherally and is
particularly low in AB cells (Brummel et
al., 1994; de Celis,
1997; Haerry et al., 1998;
Lecuit and Cohen, 1998;
Tanimoto et al., 2000)
(Fig. 4F). By contrast,
although the expression of tkv in the haltere pouch increases
slightly in the periphery, it is uniform in the central region and higher than
in the corresponding domain of the wing pouch
(Fig. 4G). In
Ubx- clones the tkv expression is reduced but for
the clones induced in the more lateral domains
(Fig. 4H-I''). Conversely,
ectopic Ubx expression in medial regions of the wing disc of
CbxTwt mutants increases tkv expression
(Fig. 4J,J'). As Tkv
levels are crucial for Dpp signaling and Dpp diffusion (Haerry et al., 1998;
Lecuit and Cohen, 1998;
Tanimoto et al., 2000;
Funakoshi et al., 2001), we
decided to examine in more detail the regulation of tkv expression by
Ubx.
In the wing pouch, the distribution of tkv is regulated by two
mechanisms (Lecuit and Cohen,
1998; Funakoshi et al.,
2001). The first mechanism depends on the activity of master
of thick veins (mtv)
(Funakoshi et al., 2001). In
AB cells, high mtv expression, under control of Hh signaling,
strongly reduces the tkv signal; in cells located in a medial
position along the A/P axis, moderate mtv expression reduces
tkv transcription to a basal level
(Funakoshi et al., 2001). An
mtv-lacZ reporter insertion is prominently expressed in the
AB cells and in two peripheral domains of the wing pouch, and expressed at low
levels in the rest of the pouch (Funakoshi
et al., 2001) (Fig.
4K). In the haltere disc, only the lateral signal remains
(Fig. 4L). This difference is
due to Ubx because in bx3/TM2 haltere
discs an A/P stripe appears (Fig.
4M) and in Ubx- clones mtv is
derepressed (Fig. 4N,N').
Reciprocally, ectopic Ubx expression in the wing disc represses
mtv in central and medial domains
(Fig. 4O,O'). Therefore,
the absence of mtv in AB cells of the haltere pouch can explain their
high levels of tkv expression and Dpp signaling. Consistently, in
MS1096-Gal4; UAS-mtv/+ larvae, in which
mtv is strongly expressed in the dorsal region of the haltere pouch,
tkv levels are partially reduced dorsally except in the more lateral
domains (Fig. 4P, the wild type
is shown in Fig. 4G).
Therefore, Ubx repression of mtv in central and medial
regions of the haltere pouch contributes to their high tkv
transcription.
|
|
; Tanimoto et al.,
2000). Thus, in MS1096-Gal4;
UAS-tkvQ253D/+ larvae tkv-lacZ
levels are reduced in the dorsal region
(Fig. 4Q). By contrast, no such
repression is observed in the haltere pouch
(Fig. 4R), indicating that
Ubx prevents the repression of tkv mediated by Dpp
signaling. Collectively, our results show that Ubx promotes high
levels of tkv in the haltere pouch by repressing mtv and by
inhibiting the Dpp signaling-mediated downregulation of tkv. However,
we cannot exclude a direct effect of Ubx on tkv.
|
;
Tanimoto et al., 2000). Given
that Ubx increases tkv expression in the haltere disc, these
high levels may retain more Dpp ligand than in the wing disc, thus explaining
the restricted Dpp diffusion and activity observed in the haltere pouch. To
confirm this, we first induced Ubx- clones in the haltere
disc and looked at the P-Mad expression pattern. In clones encompassing the
border of high P-Mad staining there is an expansion of the P-Mad signal that,
frequently, is observed outside the mutant territory
(Fig. 5A-A''). This
non-cell-autonomous effect is similar to that described previously for
omb (Fig. 2F-F'')
and suggests that Dpp extends readily through the Ubx mutant
territory inducing high levels of signaling distally to the clone.
|
Ubx controls the expression of dally
The function and distribution of Dpp, like that of Wingless (Wg) or Hh,
depends on the presence of a kind of cell-surface molecule named heparin
sulphate proteoglycans (reviewed by Lin,
2004). Two proteoglycan members in Drosophila are
dally and dlp (Nakato et
al., 1995; Khare and
Baumgartner, 2000; Baeg et al.,
2001). Both are implicated in Dpp function
(Fujise et al., 2001;
Fujise et al., 2003;
Jackson et al., 1997;
Tsuda et al., 1999;
Belenkaya et al., 2004) and in
the transport of Dpp along the A/P axis
(Belenkaya et al., 2004).
dlp is expressed at slightly lower levels in the haltere pouch than
in the wing pouch (not shown), and we have not investigated it further.
However, a different dally expression in the two discs was patent. In
the wing pouch, a dally-lacZ insertion shows high expression
in two bands along the dorsoventral (D/V) boundary and in the AB cells, with
lower signal in the rest of the pouch
(Fujise et al., 2001;
Fujise et al., 2003)
(Fig. 6A). By contrast, in the
haltere disc the expression in AB cells is missing, the D/V signal seems to be
confined to the anterior compartment (where wg is expressed) and
there are lower levels throughout the pouch
(Fig. 6B). When Ubx
expression is reduced in the haltere pouch, the pattern of dally
resembles that of the wing disc (Fig.
6C), and in clones that ectopically express Ubx in the
wing disc there is a reduction in dally signal
(Fig. 6D,D'). These
results show that Ubx is necessary and sufficient to differentiate
dally expression in both discs. Previous results demonstrated that
the ectopic expression of dally in the wing disc augments Dpp
activity (Fujise et al., 2003;
Takeo et al., 2005).
Similarly, we have observed an increase in the extent of P-Mad signal in the
dorsal domain of ap- Gal4/UAS-dally haltere discs
(Fig. 6E). We conclude that
Ubx may reduce the extent of Dpp activity in the haltere disc by
controlling dally expression.
In AB cells of the wing disc the expression of dally is induced by
Hh signaling but can be downregulated if Dpp signaling is increased
(Fujise et al., 2003).
mtv, whose expression in these cells is also induced by Hh
(Funakoshi et al., 2001), is
also downregulated if Dpp activity is elevated
(Fig. 6F). Therefore, we
wondered if the high Dpp signaling present in the AB cells of the haltere
pouch may contribute to the lack of dally and mtv
expression. If this hypothesis is correct, a reduction in Dpp signaling should
activate these two genes in the A/P boundary of the haltere disc. We found no
such dally (Fig. 6G)
or mtv (Fig. 6H)
activation when Dpp activity was decreased (in MS1096-Gal4;
UAS-tkvDN/+ larvae). The repression of
mtv and dally by Ubx in AB cells, therefore, is not
maintained by high Dpp activity.
Haltere size depends on Ubx regulation of dpp expression and spread
A major difference between wings and halteres is their size
(Fig. 7A). Although this is
mostly due to the different size of wing and haltere cells
(Roch and Akam, 2000), wing
discs are also bigger than haltere discs, even though cell size in both
structures is similar (Roch and Akam,
2000). At the end of embryogenesis, wing discs are about twice as
big as haltere discs (Morata and
García-Bellido, 1976;
Madhavan and Schneidermann,
1977; Bate and
Martínez-Arias, 1991). We have measured the size of wing
and haltere pouches in late third instar larvae and found the former to be
about 3.5-4 times bigger than the latter. Assuming that the size difference
found at the end of the embryogenesis applies equally to all regions of the
disc, this implies that the wing pouch acquires around twice as many cells as
the haltere pouch during the larval period. We have measured the size of
Ubx mutant clones, and that of their twin spots, induced during the
larval stages and analyzed in the haltere discs of late third instar larvae,
and found that they are of similar size
(Fig. 7B): the `Ubx
clone area/twin clone area' ratio is 1.06 (n=20). This suggests that
a different proliferation dynamic of Ubx-expressing cells is probably
not responsible for the smaller size of haltere discs.
|
; Capdevila and
Guerrero, 1994; Burke and
Basler, 1996; Lecuit et al.,
1996; Nellen et al.,
1996; Haerry et al., 1998;
Lecuit and Cohen, 1998;
Martín-Castellanos and Edgar,
2002; Martín et al.,
2004), we reasoned that Ubx may reduce haltere size by
regulating this signaling route. We tried to prove this assumption by
different experiments. First, we investigated whether forcing the
transcription of Dpp pathway elements, the expression of which is
downregulated by Ubx, may impinge on haltere size. Overexpression of
dpp in its own domain increases the size of the haltere pouch
(Fig. 7C). The ectopic
expression of dally or mtv also augments haltere size: we
have measured the width of A and P compartments in the haltere pouches of
en-Gal4 UASGFP/+, en-Gal4 UAS-GFP/UAS-dally and
en-Gal4 UASGFP/UAS-mtv larvae (all grown at 29°C), and
found that the ectopic expression of dally or mtv increases
the P/A width ratio by 21% and 35%, respectively, with respect to the control
discs (Fig. 7D-F,U). This
difference is probably not due to the effect of dally on Hh and Wg
signaling (reviewed by Lin,
2004) because wg is not expressed
(Weatherbee et al., 1998) and
hh is not active
(Domínguez et al.,
1996; Hepker et al.,
1997) in this compartment.
As a second test, we studied whether there was a phenotypic interaction
between dpp and Ubx as regards to haltere size. dpp
hypomorphic mutations reduce the size of the distal part of the halteres (the
capitellum) (Spencer et al.,
1982) (Fig. 7H
compare with the wild type in 7G). In a mutant background heterozygous for
Ubx, the dpp- vestigial phenotype is partially
suppressed (Fig. 7I),
suggesting that a reduction in Ubx can make up for the low Dpp
levels. Several experiments argue that this interaction relies, at least in
part, in the control by Ubx of tkv expression. First, wings
are smaller (without apparent change in cell size, as judged by trichome size
and density) if Ubx (Fig.
7K, compare with the wild type in 7J) or tkv (Haerry et
al., 1998; Lecuit and Cohen,
1998; Tanimoto et al.,
2000) (Fig. 7L) are
present in AB cells. Second, in Ubx/+ adults the capitellum is
enlarged (Fig. 7M), and this
phenotype is stronger in sibling flies that are also heterozygous for a
tkv deficiency (Fig.
7N). Finally, the increase in the size of the posterior or
anterior compartments in pbx- or bx-mutant haltere discs
(Fig. 7O,Q) is partially
reverted when tkv levels are elevated
(Fig. 7P,R): the P/A width
ratio in pbx/Ubx6.28 haltere discs is reduced by
37% in en-Gal4 UAS-GFP/+; pbx/UAS-tkv
Ubx6.28 larvae and the A/P width ratio in
bx3/Ubx6.28 haltere discs is reduced
by 17% in ptc-Gal4 UASGFP/+; bx3/UAS-tkv
Ubx6.28 larvae (Fig.
7U). The latter reduction is modest probably because the
ptc-Gal4 driver expresses tkv only in part of the anterior
compartment and because dpp expression is wing-like. As a summary,
our results suggest that Ubx reduces the size of the haltere, as
compared with the wing, in part through the expression of tkv.
We have demonstrated that the absence of Ubx in mutant clones affects Dpp activity both cell autonomously and non-cell autonomously (Fig. 2F-F'' and Fig. 5A-A''), and that Ubx hinders Dpp spread. Therefore, local changes in Ubx expression may have non-cell-autonomous effects on size. To prove this, we reared larvae of the ptc-Gal4 UAS-GFP/+; Df109 UAS-dsRNA>Ubx/tub-Gal80ts genotype at 17°C and transferred them to 29°C at the second or early third larval stage. This procedure eliminates Ubx expression in the ptc domain (not shown). In many of the flies that underwent this treatment we observed that the anterior haltere tissue was bigger than that expected to derive from the Ubx-expressing region, sometimes even bigger than a whole anterior haltere compartment (Fig. 7S,S'). A similar effect was observed in flies in which the absence of Ubx is clonally inherited (ptc-Gal4/UAS-flp; FRT Ubx6-28/FRT GFP flies; Fig. 7T). This suggests that the absence of Ubx in anterior border cells increases the growth of the more anterior, Ubx-expressing haltere region.
|
|
DISCUSSION |
|---|
|
TOPSUMMARYINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
;
Barrio et al., 1999;
Shashidhara et al., 1999;
Galant et al., 2002;
Mohit et al., 2003;
Mohit et al., 2006;
Pallavi et al., 2006). We show
here that Ubx controls the Dpp signaling pathway at different levels
and that this regulation contributes significantly to the different sizes of
these two appendages. Similar results have also been recently reported
(Crickmore and Mann,
2006).
|
;
Capdevila and Guerrero, 1994;
Tabata and Kornberg, 1994),
and in the haltere pouch Ubx attenuates this activation
(Mohit et al., 2006) (this
report). The haltere dpp stripe increases slightly in pbx
mutations, showing a non-cell-autonomous effect that is perhaps due to an
increase in the numbers of cells expressing hh. However, the major
control of dpp expression by Ubx is cell autonomous.
Ubx also governs Dpp spread and activity. A mechanism whereby
Ubx may limit the spread of Dpp is by reducing dally
expression. The protein encoded by this gene seems to be required to transmit
the Dpp protein from cell to cell (Belankaya et al., 2004), and we have shown
that Ubx downregulates dally expression, thus reducing the
extent of Dpp activity. Ubx retards Dpp spread also by augmenting
tkv expression (mainly at the A/P boundary and not in the periphery)
because high Tkv levels retain the Dpp morphogen (Haerry et al., 1998;
Lecuit and Cohen, 1998;
Tanimoto et al., 2000)
(Fig. 8B,C). In
Ubx- clones, the Dpp product can `travel' more readily
through the mutant cells, thus extending Dpp signaling not only within the
clone but also in more distal cells (Fig.
8D). If we elevate tkv expression in these clones, Dpp
spread is checked, preventing the non-cell autonomous and reducing the extent
of the cell-autonomous effect on Dpp signaling
(Fig. 8E).
The increased tkv transcription and the suppression of
dally expression have a double effect. On the one hand, they reduce
Dpp spread; on the other hand, they increase Dpp activity in AB cells. In the
wing disc, Hh signaling strongly diminishes Dpp signaling in this domain by
inducing mtv and dally transcription; this reduction is
required for the correct pattern of the central region of the wing and for
substantial dally and mtv expression
(Tanimoto et al., 2000;
Fujise et al., 2001;
Funakoshi et al., 2001;
Fujise et al., 2003) (this
report). By contrast, our results demonstrate that Ubx allows high
levels of both Dpp and Hh activity in these cells of the haltere disc, and
that repression of mtv and dally is not maintained by this
high Dpp signaling. This suggests that a different mechanism for patterning
this domain is acting in haltere and wing discs. Finally, the Ubx
modulation of Dpp activity is complex. Whereas Ubx prevents Dpp
signaling from downregulating tkv or mtv in the periphery of
the haltere pouch, in MS1096; UAS-tkvQD haltere
discs dpp-lacZ expression in the dorsal region is completely
suppressed (not shown).
Haltere size control by the Ubx product
Several lines of evidence argue that differences in dpp, tkv and
probably dally expression, all of them controlled by Ubx,
may be instrumental in reducing the size of the haltere disc compared with
that of the wing disc: first, Ubx downregulates dpp
transcription, and the increased expression of dpp augments the size
of haltere discs (see also Mohit et al.,
2006); second, Ubx increases tkv expression, and
the ectopic Ubx expression, or the elevated tkv
transcription, reduces wing size (Haerry et al., 1998;
Lecuit and Cohen, 1998;
Tanimoto et al., 2000) (this
report); third, the ectopic expression of mtv or dally (both
increasing Dpp spread) in the posterior compartment of the haltere disc
substantially increases its size; fourth, the reduction of tkv
expression increases the haploinsufficient phenotype of the Ubx locus
and, conversely, reduced Ubx levels partially rescue the small
halteres of dpp hypomorphic mutations; finally, the increased size of
the haltere disc observed in pbx or bx mutations is
partially suppressed if Tkv levels are increased.
The control of size by Ubx relies on the reduction of dpp
expression and Dpp spread. Thus, it is not surprising that it involves
non-cell-autonomous effects. We have shown that if Ubx is removed
from the central region of the haltere pouch, this domain is transformed into
wing, but the remaining haltere tissue is bigger than expected. This occurs
with Gal4 lines that drive a dsRNA>Ubx construct or when
Ubx mutant clones are induced in the anterior compartment of the
haltere disc. These results suggest that Dpp spread is increased within the
mutant region so that more Dpp reaches the distal haltere domain. As a result,
differences in Dpp activity between adjacent cells extend over a larger
domain, and both the region that is transformed into wing and the tissue that
remains as haltere, increase their size. The growth control is, in part,
non-cell autonomous, but the differentiation is strictly cell autonomous
(Morata and García-Bellido,
1976; Hart and Bienz,
1996; Roch and Akam,
2000). A non-cell autonomous role of Ubx on organ size
has also been described in the development of the third leg
(Stern, 2003). Our
observations may explain some previous results: first, in pbx and
bx mutants there is a slight increase in the size of the
untransformed compartment compared with wild-type flies
(González-Gaitán et al.,
1990), perhaps because dpp expression is higher. Second,
if wing and haltere tissues are confronted in the wing disc of
Contrabithorax mutations (which partially transform wing into
haltere), the haltere (transformed) tissue is also bigger than expected
(González-Gaitán et al.,
1990), possibly because dpp expression and spread are
increased. Third, by changing the activity of Ubx during development
with the temperature-sensitive bx1 mutation, halteres
bigger than normal are observed
(Sánchez-Herrero and Morata,
1983), maybe because the initial growth (wing-like) and the
posterior haltere differentiation are relatively uncoupled. However, although
we stress the role of the Dpp pathway in regulating the size of the haltere,
we are aware that other factors are also likely to contribute to this effect.
For instance, wingless is not expressed in the posterior compartment
of the haltere disc, and this absence has been correlated with its small size
(Weatherbee et al., 1998).
It is unclear how these effects on the Dpp pathway are translated into a
reduction in disc size as cell size is similar in both discs
(Roch and Akam, 2000).
Recently, Rogulja and Irvine (Rogulja and
Irvine, 2005) have proposed a model to account for the
proliferation in the wing disc. This model proposes that differences in Dpp
signaling in the medial and lateral regions of the wing disc induce
non-cell-autonomous proliferation for a short time. A similar mechanism may
exist in the proliferation of the haltere discs because both discs give rise
to homologous structures and rely on similar patterning cues. In the haltere
disc, both the lower amount of Dpp synthesized and its lower spread result in
a more narrow and sharp Dpp activity gradient. We have shown that a gradient
of Dpp-GFP signal is established in medial regions of the wing but not the
haltere discs. This will extend the differences in Dpp signaling between
adjacent cells further in the wing disc, perhaps allowing for more cells to
enter division at early larval stages. Madhavan and Schneidermann
(Madhavan and Schneidermann,
1977) reported a slight delay in cells of the haltere disc
reassuming division after embryogenesis compared with the wing disc, and a
somewhat bigger cell-doubling time at the beginning of the second instar.
Previous results indicated that the variation in clone size is similar in
haltere or wing discs throughout larval stages
(Morata and García-Bellido,
1976); in this experiment, however, it was assumed that each
haltere cell secreted one trichome whereas a later study showed that haltere
cells can secrete more than one (Roch and
Akam, 2000). Our results indicate that Ubx does not seem
to delay cell division autonomously, and that it is necessary to mutate a big
region of the haltere disc to observe a clear size difference.
In the grasshopper, the increased expression of dpp in the
metathoracic legs has been suggested to account for the larger size of these
appendages (Niwa et al.,
2000), and we propose that changes in dpp transcription
and Dpp spread underlie size differences between halteres and wings. The
regulation of morphogen levels and of proteins that limit the movement of the
ligand (such as Tkv and Dally) by Hox genes may be a general mechanism used in
evolution to differentiate size in homologous organs within a certain animal,
or between homologous organs in different species. Because the Dpp pathway
also controls pattern, Ubx may differentiate the size and pattern in
halteres and wings, coordinating both processes by a single mechanism through
the change in the amount and distribution of the Dpp product.
Note added in proof
Similar results to those described here have been recently reported by
Makhijani, K., Kalyani, C., Srividya, T. and Shashidhara, L. S. Modulation of
Decapentaplegic morphogen gradient during haltere specification in
Drosophila. Dev. Biol. (in press).
Supplementary material
Supplementary material for this article is available at
http://dev.biologists.org/cgi/content/full/133/22/4495/DC1
|
ACKNOWLEDGMENTS |
|---|
|
REFERENCES |
|---|
|
TOPSUMMARYINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
Azpiazu, N. and Frasch, M. (1993).
tinman and bagpipe: two homeo box genes that determine cell
fates in the dorsal mesoderm of Drosophila. Genes Dev.
7,1325
-1340.
Baeg, G. H., Lin, X., Khare, N., Baumgartner, S. and Perrimon, N. (2001). Heparan sulphate proteoglycans are critical for the organization of the extracellular distribution of wingless.Development 128,87 -94.[Abstract]
Barrio, R., de Celis, J. F., Bolshakov, S. and Kafatos, F. (1999). Identification of regulatory regions driving the expression of the Drosophila spalt complex at different developmental stages. Dev. Biol. 215,33 -47.[CrossRef][Medline]
Basler, K. and Struhl, G. (1994). Compartment boundaries and the control of Drosophila limb pattern by Hedgehog protein. Nature 368,208 -214.[CrossRef][Medline]
Bate, M. and Martínez-Arias, A. (1991). The embryonic origin of imaginal discs in Drosophila.Development 112,755 -761.[Abstract]
Beachy, P. A., Helfand, S. L. and Hogness, D. S. (1985). Segmental distribution of bithorax complex proteins during Drosophila development. Nature 313,545 -551.[CrossRef][Medline]
Belenkaya, T. Y., Han, C., Yan, D., Opoka, R. J., Khodoun, M., Liu, H. and Lin, X. (2004). Drosophila Dpp morphogen development is independent of dynamin-mediated endocitosis but regulated by the glypican members of the heparan sulfate proteoglycans. Cell 119,231 -244.[CrossRef][Medline]
Bender, W., Akam, M., Karch, F., Beachy, P. A., Peifer, M.,
Spierer, P., Lewis, E. B. and Hogness, D. S. (1983).
Molecular genetics of the Bithorax Complex in Drosophila melanogaster.
Science 221,23
-29.
Blackman, R. K., Sanicola, M., Raftery, L. A., Gillevet, T. and Gelbart, W. (1991). An extensive 3' cis-regulatory region directs the imaginal disc expression of decapentaplegic, a member of the TGF-ß family in Drosophila.Development 111,657 -665.[Abstract]
Brand. A. and Perrimon, N. (1993). Targeted gene expression as a means of altering cell fates and generating dominant phenotypes. Development 118,401 -415.[Abstract]
Brummel, T. J., Twombly, V., Marqués, G., Wrana, J. L., Newfeld, S. J., Attisano, L., Massagué, J., O'Connor, M. B. and Gelbart, W. M. (1994). Characterization and relationship of Dpp receptors encoded by the saxophone and thick veins genes of Drosophila. Cell 78,251 -261.[CrossRef][Medline]
Burke, R. and Basler, K. (1996). Dpp receptors are autonomously required for cell proliferation in the entire developing Drosophila wing. Development 122,2261 -2269.[Abstract]
Cabrera, C., Botas, J. and García-Bellido, A. (1985). Distribution of Ultrabithorax proteins in mutants of Drosophila bithorax complex and its transregulatory genes. Nature 318,569 -571.[CrossRef]
Calleja, M., Moreno, E., Pelaz, S. and Morata, G.
(1996). Visualization of gene expression in living adult
Drosophila. Science 274,252
-255.
Campbell, G. and Tomlinson, A. (1999). Transducing the Dpp morphogen gradient in the wing of Drosophila: regulation of Dpp targets by brinker. Cell 96,553 -562.[CrossRef][Medline]
Capdevila, J. and Guerrero, I. (1994). Targeted expression of the signal molecule decapentaplegic induces patern duplications and growth alterations in Drosophila wings. EMBO J. 13,4459 -4468.[Medline]
Castelli-Gair, J., Greig, S., Micklem, G. and Akam, M. (1994). Dissecting the temporal requirements for homeotic gene function. Development 120,1983 -1995.[Abstract]
Chen, Y. and Struhl, G. (1996). Dual roles for Patched in sequestering and transducing Hedgehog. Cell 87,553 -563.[CrossRef][Medline]
Crickmore, M. A. and Mann, R. S. (2006). Hox
control of organ size by regulation of morphogen production and mobility.
Science 313,63
-68.
Day, S. J. and Lawrence, P. A. (2000). Measuring dimensions: the regulation of size and shape. Development 127,2977 -2987.[Abstract]
de Celis, J. F. (1997). Expression and function of decapentaplegic and thick veins during the differentiation of the veins in the Drosophila wing. Development 124,1007 -1018.[Abstract]
Domínguez, M., Brunner, M., Hafen, E. and Basler, K. (1996). Sending and receiving the hedgehog signal: control by the Drosophila Gli protein Cubitus interruptus.Science 272,1621 -1625.[Abstract]
Entchev, E. V., Schwabedissen, A. and González-Gaitán, M. (2000). Gradient formation of the TGF-ß homolog Dpp. Cell 103,981 -991.[CrossRef][Medline]
Estrada, B. and Sánchez-Herrero, E. (2001). The Hox gene Abdominal-B antagonizes appendage development in the genital disc of Drosophila.Development 128,331 -339.[Abstract]
Fujise, M., Izumi, S., Selleck, S. B. and Nakato, H. (2001). Regulation of dally, an integral membrane proteoglycan, and its function during adult sensory organ formation of Drosophila. Dev. Biol. 235,433 -448.[CrossRef][Medline]
Fujise, M., Takeo, S., Kamimura, K., Matsuo, T., Aigaki, T.,
Izumi, S. and Nakato, H. (2003). Dally regulates Dpp
morphogen gradient formation in the Drosophila wing.
Development 130,1515
-1522.
Funakoshi, Y., Minami, M. and Tabata, T. (2001). mtv shapes the activity gradient of the Dpp morphogen through regulation of thickveins.Development 128,67 -74.[Abstract]
Galant, R., Walsh, C. M. and Carroll, S. B.
(2002). Hox repression of a target gene:
extradenticle-independent, additive action through multiple monomer
binding sites. Development
129,3115
-3126.
García-Bellido, A., Ripoll, P. and Morata, G. (1973). Developmental compartmentalization of the wing disc of Drosophila. Nature New Biol. 245,251 -253.[CrossRef][Medline]
González-Gaitán, M. A., Micol, J. L. and García-Bellido, A. (1990). Developmental genetic analysis of Contrabithorax mutations in Drosophila melanogaster.Genetics 126,139 -155.[Abstract]
Grimm, S. and Pflugfelder, G. O. (1996). Control of the gene optomotor-blind in Drosophila wing development by decapentaplegic and wingless. Science 271,1601 -1604.[Abstract]
Haerry, T. E., Khalsa, O., O'Connor, M. B. and Wharton, K. A. (1988). Synergistic signaling by two BMP ligands through the SAX and TKV receptors controls wing growth and patterning in Drosophila. Development 125,3977 -3987.
Hart, K. and Bienz, M. (1996). A test for cell autonomy, based on di-cistronic messenger translation. Development 122,747 -751.[Abstract]
Hepker, J., Wang, Q.-T., Motzny, C. K., Holmgreen, R. and Orenic, T. V. (1997). Drosophila cubitus interruptus forms a negative feedback loop with patched and regulates expression of Hedgehog target genes. Development 124,549 -558.[Abstract]
Hinz, U., Giebel, B. and Campos-Ortega, J. A. (1994). The basic helix-loop-helix of Drosophila lethal of scute protein is sufficient for pro-neural function and activates neurogenic genes. Cell 76, 77-87.[CrossRef][Medline]
Ito, K., Awano, W., Suzuki, K., Hiromi, Y. and Yamamoto, D. (1997). The Drosophila mushroom body is a quadruple structure of clonal units each of which contains a virtually identical set of neurones and glial cells. Development 124,761 -771.[Abstract]
Jackson, S. M., Nakato, H., Sugiura, M., Jannuzi, A., Oakes, R., Kaluza, V., Golden, C. and Selleck, S. B. (1997). Dally, a Drosophila glypican, controls cellular responses to the TGF-beta-related morphogen Dpp. Development 124,4113 -4120.[Abstract]
Jazwinska, A., Kirov, N., Wieschaus, E., Roth, S. and Rushlow, C. (1999). The Drosophila gene brinker reveals a novel mechanism of Dpp target regulation. Cell 93,563 -573.
Khare, N. and Baumgartner, S. (2000). Dally-like protein, a new Drosophila glypican with expression overlapping with wingless. Mech. Dev. 99,199 -202.[CrossRef][Medline]
Lecuit, T. and Cohen, S. M. (1998). Dpp receptor levels contribute to shaping the Dpp morphogen gradient in the Drosophila wing imaginal disc. Development 125,4901 -4907.[Abstract]
Lecuit, T., Brook, W. J., Ng, M., Calleja, M., Sun, H. and Cohen, S. M. (1996). Two distinct mechanisms for long-range patterning by Decapentaplegic in the Drosophila wing. Nature 381,387 -193.[CrossRef][Medline]
Lee, J. J., von Kessler, D. P., Parks, S. and Beachy, P. A. (1992). Secretion and localized transcription suggests a role in positional signalling for products of the segmentation gene hedgehog.Cell 71,33 -50.[CrossRef][Medline]
Lee, T. and Luo, L. (1999). Mosaic analysis with a repressible neurotechnique cell marker for studies of gene function in neuronal morphogenesis. Neuron 22,451 -461.[CrossRef][Medline]
Lewis, E. B. (1952). The pseudoallelism of
white and apricot in Drosophila melanogaster.Proc. Natl. Acad. Sci. USA
38,953
-961.
Lewis, E. B. (1963). Genes and developmental pathways. Am. Zool. 3,33 -56.
Lewis, E. B. (1978). A gene complex controlling segmentation in Drosophila. Nature 276,565 -570.[CrossRef][Medline]
Lin, X. (2004). Functions of heparin sulphate
proteoglycans in cell signaling during development.
Development 131,6009
-6021.
Madhavan, M. M. and Schneidermann, H. A. (1977). Histological analysis of the dynamics of growth of imaginal discs and histoblasts nests during the larval development of Drosophila melanogaster. Wilhelm Roux's Arch. Dev. Biol. 183,269 -305.[CrossRef]
Martín, F. A., Pérez-Garijo, A., Moreno, E. and
Morata, G. (2004). The brinker gradient controls
wing growth in Drosophila. Development
131,4921
-4930.
Martín-Castellanos, C. and Edgar, B. A. (2002). A characterization of the effects of Dpp signaling on cell growth and proliferation in the Drosophila wing. Development 129,1003 -1013.[Medline]
McGinnis, W. and Krumlauf, R. (1992). Homeobox genes and axial patterning. Cell 24,283 -302.
McGuire, S. E., Le, P. T., Osborn, A. J., Matsumoto, K. and
Davis, R. L. (2003). Spatiotemporal rescue of memory
dysfunction in Drosophila. Science
302,1765
-1768.
Minami, M., Kinoshota, N., Kamoshida, Y., Tanimoto, H. and Tabata, T. (1999). Brinker is a target of Dpp in Drosophila that negatively regulates Dpp-dependent genes. Nature 398,242 -246.[CrossRef][Medline]
Mohit, P., Bajpai, R. and Shashidhara, L. S.
(2003). Regulation of wingless and vestigial
expression in wing and haltere discs of Drosophila.Development 130,1537
-1547.
Mohit, P., Makhijani, K., Madhavi, M. D., Bharati, V., Lal, A., Sirdesai, G., Ram Reddy, V., Ramesh, P., Kannan, R., Dhawan, J. et al. (2006). Modulation of AP and DV signaling pathways by the homeotic gene Ultrabithorax during haltere development in Drosophila. Dev. Biol. 291,356 -367.[CrossRef][Medline]
Monier, B., Astier, M., Sémériva, M. and Perrin.
L. (2005). Steroid-dependent modification of Hox function
drives myocyte reprogramming in the Drosophila heart.
Development 132,5283
-5293.
Morata, G. and García-Bellido, A. (1976). Developmental analysis of some mutants of the bithorax system of Drosophila. Wilhelm Roux's Arch. Dev. Biol. 179,125 -143.[CrossRef]
Morimura, S., Maves, L., Chen, Y. and Hoffmann, F. M. (1996). Decapentaplegic overexpression affects Drosophila wing and leg imaginal disc development and wingless expression. Dev. Biol. 177,136 -151.[CrossRef][Medline]
Nakato, H., Futch, T. A. and Selleck, S. B. (1995). The division abnormally delayed (dally) gene: a putative integral membrane proteoglycan required for cell division patterning during postembryonic development of the nervous system of Drosophila. Development 121,3687 -3702.[Abstract]
Nellen, D., Burke, R., Struhl, G. and Basler, K. (1996). Direct and long-range action of a Dpp morphogen gradient. Cell 85,357 -368.[CrossRef][Medline]
Newfeld, S. J., Mehra, A., Singer, M. A., Wrana, J. L., Attisano, L. and Gelbart, W. M. (1997). Mothers against dpp participates in a DPP/TGF-B responsive serine-threonine kinase signal transduction cascade. Development 124,3167 -3176.[Abstract]
Niwa, N., Inoue, Y., Nozawa, A., Saito, M., Misumi, Y., Ohuchi, H., Yoshioka, H. and Noji, S. (2000). Correlation of diversity of leg morphology in Gryllus bimaculatus (cricket) with divergence in dpp expression pattern during leg development. Development 127,4373 -4381.[Abstract]
Pallavi, S. K., Kannan, R. and Shashidhara, L. S. (2006). Negative regulation of Egfr/Ras pathway by Ultrabithorax during haltere development in Drosophila.Dev. Biol. 296,340 -352.[CrossRef][Medline]
Patel, N. H., Martín-Blanco, E., Coleman, K. G., Poole, S. J., Ellis, M. C., Kornberg, T. B. and Goodman, C. S. (1989). Expression of engrailed proteins in arthropods, annelids and chordates. Cell 58,955 -968.[CrossRef][Medline]
Persson, U., Izumi, H., Souchelnytskyi, S., Itoh, S., Grimsby, S., Engstrom, U., Heldin, C. H., Funa, K. and ten Dijke, P. (1998). The L45 loop in type I receptors for TGF-beta family members is a critical determinant inspecifying Smad isoform activation. FEBS Lett. 434,83 -87.[CrossRef][Medline]
Pignoni, F. and Zipurski, S. (1997). Induction of Drosophila eye development by Decapentaplegic. Development 124,271 -278.[Abstract]
Posakony, L. G., Raftery, L. A. and Gelbart, W. M. (1991). Wing formation in Drosophila melanogaster requires decapentaplegic gene function along the anterior-posterior compartment boundary. Mech. Dev. 33,69 -82.
Roch, F. and Akam, M. (2000). Ultrabithorax and the control of cell morphology in Drosophila halteres. Development 127,97 -107.[Abstract]
Rogulja, D. and Irvine, K. D. (2005). Regulation of cell proliferation by a morphogen gradient. Cell 123,449 -451.[CrossRef][Medline]
Sánchez-Herrero, E. (1991). Control of the expression of the bithorax complex genes abdominal-A and Abdominal-B by cis-regulatory regions in Drosophila embryos. Development 111,437 -449.[Abstract]
Sánchez-Herrero, E. and Morata, G. (1983). Genetic and developmental characteristics of the homeotic mutation bx1 of Drosophila. J. Embryol. Exp. Morphol. 76,251 -264.[Medline]
Shashidhara, L. S., Agrawal, N., Bajpai, R., Bharati, V. and Sinha, P. (1999). Negative regulation of dorsovental signaling by the homeotic gene Ultrabithorax during haltere development in Drosophila. Dev. Biol. 212,491 -502.[CrossRef][Medline]
Spencer, F. A., Hoffmann, F. M. and Gelbart, W. M. (1982). Decapentaplegic: a gene complex affecting morphogenesis in Drosophila melanogaster. Cell 28,451 -461.[CrossRef][Medline]
St Johnston, D. R., Hoffmann, F. M., Blackman, R. K., Segal, D.,
Grimalia, R., Padgett, R. W., Irick, H. A. and Gelbart, W. M.
(1990). Molecular organization of the decapentaplegic
gene in Drosophila melanogaster. Genes Dev.
4,1114
-1127.
Stern, D. L. (2003). The Hox gene Ultrabithorax modulates the shape and the size of the third leg of Drosophila by influencing diverse mechanisms. Dev. Biol. 256,355 -366.[CrossRef][Medline]
Szidonya, J. and Reuter, G. (1988). Cytogenetics of the 24D4-25F2 region of the Drosophila melanogaster 2L chromosome. Drosoph. Inf. Serv. 67, 77-79.
Tabata, T. (2001). Genetics of morphogen gradients. Nat. Rev. Genet. 2, 620-630.[CrossRef][Medline]
Tabata, T. and Kornberg, T. B. (1994). Hedgehog is a signalling protein with a key role in patterning Drosophila imaginal discs. Cell 76,89 -102.[CrossRef][Medline]
Tabata, T., Schwartz, C., Gustavson, E., Ali, Z. and Kornberg, T. B. (1995). Creating a Drosophila wing de novo: the role of engrailed, and the compartment boundary hypothesis. Development 121,3359 -3369.[Abstract]
Takeo, S., Akiyama, T., Firkus, C., Aigaki, T. and Nakato, H. (2005). Expression of a secreted form of Dally, a Drosophila glypican, induces overgrowth phenotype by affecting the action range of Hedgehog. Dev. Biol. 284,204 -218.[CrossRef][Medline]
Tanimoto, H., Itoh, S., ten Dijke, P. and Tabata, T. (2000). Hedgehog creates a gradient of Dpp activity in Drosophila wing imaginal discs. Mol. Cell 5, 59-71.[CrossRef][Medline]
Teleman, A. A. and Cohen, S. (2000). Dpp gradient formation in the Drosophila wing imaginal disc. Cell 103,971 -980.[CrossRef][Medline]
Terracol, R. and Lengyel, J. A. (1994). The thick veins gene of Drosophila is required for dorsoventral polarity of the embryo. Genetics 138,165 -178.[Abstract]
Tsuda, M., Kamimura, K., Nakato, H., Archer, M., Staatz, W., Fox, B., Humphrey, M., Olson, S., Futch, T., Kaluza, V. et al. (1999). The cell surface proteoglycan Dally regulates Wingless signalling in Drosophila. Nature 400,276 -280.[CrossRef][Medline]
Tsuneizumi, K., Nakayama, T., Kamoshida, Y., Kornberg, T. B., Christian, J. L. and Tabata, T. (1997). Daugthers against dpp modulates dpp organizing activity in Drosophila wing development. Nature 389,627 -631.[CrossRef][Medline]
Twombly, V., Blackman, R. K., Jin, H., Graff, J. M., Padgett, R. W. and Gelbart, W. M. (1996). The TGF-ß signalling pathway is essential for Drosophila oogenesis. Development 122,1555 -1565.[Abstract]
Weatherbee, S. D., Halder, G., Kim, J., Hudson, A. and Carroll,
S. (1998). Ultrabithorax regulates genes at several
levels of the wing-patterning hierarchy to shape the development of the
Drosophila haltere. Genes Dev.
12,1474
-1482.
White, R. A. H. and Wilcox, M. (1984). Protein products of the Bithorax complex of Drosophila. Cell 39,163 -171.[CrossRef][Medline]
White, R. A. H. and Akam, M. E. (1985). Contrabithorax mutations cause inappropriate expression of Ultrabithorax products in Drosophila. Nature 318,567 -569.[CrossRef]
White, R. A. H. and Wilcox, M. (1985). Regulation of the distribution of Ultrabithorax proteins in Drosophila. Nature 318,563 -567.[CrossRef]
Wolff, T. (2000). Histological techniques or the Drosophila eye. Part I: larva and pupa. In Drosophila Protocols (ed. W. Sullivan, M. Ashburner and R. S. Hawley), pp.201 -227. New York: Cold Spring Harbor Laboratory Press.
Xu, T. and Rubin, G. M. (1993). Analysis of genetic mosaics in developing and adult Drosophila tissues. Development 117,1223 -1237.[Abstract]
Zecca, M., Basler, K. and Struhl, G. (1995). Sequential organizing activities of engrailed, hedgehog and decapentaplegic in the Drosophila wing. Development 121,2265 -2278.[Abstract]
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati 
Twitter What's this?
Related articles in Development:
This article has been cited by other articles:
|
|
 |
|
  L. A. Baena-Lopez, I. Rodriguez, and A. Baonza The tumor suppressor genes dachsous and fat modulate different signalling pathways by regulating dally and dally-like PNAS, July 15, 2008; 105(28): 9645 - 9650. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 G. Lebreton, C. Faucher, D. L. Cribbs, and C. Benassayag Timing of Wingless signalling distinguishes maxillary and antennal identities in Drosophila melanogaster Development, July 1, 2008; 135(13): 2301 - 2309. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 I. Gonzalez, R. Aparicio, and A. Busturia Functional Characterization of the dRYBP Gene in Drosophila Genetics, July 1, 2008; 179(3): 1373 - 1388. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. A. Crickmore and R. S. Mann Hox control of morphogen mobility and organ development through regulation of glypican expression Development, January 15, 2007; 134(2): 327 - 334. [Abstract] [Full Text] [PDF]
|
|
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
