|
|
|
|
|
|
|
||||
| Home Help Feedback Subscriptions Archive Search Table of Contents | ||||
First published online 18 October 2006
doi: 10.1242/dev.02646
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Department of Biological Science and Technology, Faculty of Engineering, The University of Tokushima, 2-1 Minami-Josanjima-cho, Tokushima City 770-8506, Japan.
Author for correspondence (e-mail:
noji{at}bio.tokushima-u.ac.jp)
Accepted 14 September 2006
 |
SUMMARY |
|---|
TOP
SUMMARY
INTRODUCTION
MATERIALS AND METHODS
RESULTS
DISCUSSION
REFERENCES |
|---|
Key words: Gryllus bimaculatus, Intermediate-germband insect, brachyenteron, caudal, Posterior patterning, RNA interference
|
INTRODUCTION |
|---|
|
TOP
SUMMARY
INTRODUCTION
MATERIALS AND METHODS
RESULTS
DISCUSSION
REFERENCES |
|---|
). In
short- and intermediate-germband insects, anterior segments are specified
almost simultaneously at the blastoderm stage, whereas posterior segments are
sequentially produced from the posterior growth zone, and invagination of the
posterior gut starts after AP axial elongation from the growth zone. Thus,
because this major difference in the developmental process of posterior
patterning is observed among insects, changes in the mechanisms underlying
this process are assumed to be key events in the evolutionary transition from
short- and intermediate- to long-germband embryogenesis. However, we still do
not know how the transition occurred at the molecular level, because the
posterior patterning mechanisms in short- and intermediate-germband insects
remain poorly understood.
Recent functional studies using RNA interference (RNAi) in short- and
intermediate-germband insects have demonstrated that several transcription
factors, including Caudal (Cad), Even-skipped (Eve) and Hunchback (Hb), and
cellular signaling pathways, including Wingless (Wg)/Armadillo (Arm) and Torso
signaling, are involved in elongation and/or segmentation from the posterior
growth zone (Copf et al., 2004;
Liu and Kaufman, 2004;
Liu and Kaufman, 2005;
Mito et al., 2005;
Miyawaki et al., 2004;
Schoppmeier and Schröder,
2005; Shinmyo et al.,
2005). This has led to two tentative conclusions regarding the
evolution of genetic mechanisms directing posterior patterning. First, because
a number of homologs of these factors are involved in posterior terminal
patterning in Drosophila, the terminal system found in
Drosophila may be involved in AP axial specification from the growth
zone. Second, because homologs of some of these factors are also involved in
AP axial elongation from the primitive streak and tail bud in vertebrates,
there may be common mechanisms for AP axial formation between arthropods and
vertebrates. These hypotheses prompted us to investigate the role of the
Brachyury/brachyenteron (Bra/byn) gene, which is
involved in morphogenesis of the posterior gut in Drosophila and AP
axial elongation in vertebrates, in short- and intermediate-germband
insects.
Bra/byn is the best-characterized T-box gene and has been isolated
from many organisms. In vertebrates, Bra is expressed transiently
around the blastopore during gastrulation, in the involuting mesoderm and
endoderm, and subsequently its expression becomes restricted to the notochord
and tailbud (Herrmann, 1991;
Kispert and Herrmann, 1994;
Kispert et al., 1995;
Schulte-Merker et al., 1992;
Smith et al., 1991;
Wilkinson et al., 1990). Mouse
(Wilson and Beddington, 1997;
Wilson et al., 1995) and
zebrafish (Melby et al., 1996;
Schulte-Merker et al., 1994)
mutants demonstrate that Bra is necessary for gastrulation, axial
specification and caudal morphogenesis. Within arthropods, byn
expression and function have been most extensively investigated in D.
melanogaster. Drosophila byn (Dm'byn) is expressed in
the posterior terminal region from 0 to 
20% egg length at the blastoderm
stage, where the primordia of the posterior gut and anal pads are located, and
continues to be expressed in the hindgut and anal pads throughout
embryogenesis (Kispert et al.,
1994). In Dm'byn mutant embryos, programmed cell
death occurs in primordia of the hindgut and anal pads, resulting in a severe
reduction of their structures (Kispert et
al., 1994; Singer et al.,
1996). Additionally, Dm'byn is known to be
involved in the formation of the midgut constrictions, elongation of the
Malpighian tubules and specification of the visceral mesoderm in
Drosophila embryos (Kusch and
Reuter, 1999; Singer et al.,
1996). Conserved expression patterns of Byn were reported in the
short-germband insects Locusta migratoria and Tribolium
castaneum using the anti-TN1-123 antibody that binds specifically to the
Byn protein in Drosophila embryos
(Kispert et al., 1994).
However, the precise expression patterns and functions of byn have
not been investigated in short- and intermediate-germband insects.
We have examined byn in the intermediate-germband cricket Gryllus bimaculatus. Gryllus byn (Gb'byn) is expressed in the posterior terminal cells of the embryo during AP axial elongation, and continues to be expressed in the hindgut during late embryogenesis. Reduction of the Gb'byn expression level by RNAi resulted in defects in the posterior gut, but not in the posterior body segments. These results indicate that Gb'byn is not required for AP axial elongation or normal segment formation, but is required for morphogenesis of the posterior gut. We also examined the function of Gryllus caudal (Gb'cad) in posterior patterning by RNAi, and found that Gb'cad is required for internalization of the posterior gut primordium, in addition to AP axial elongation. We compare cad and byn function in Gryllus with their function in other bilaterians, and discuss the evolution of Cdx/cad and Bra/byn function in other animals.
|
MATERIALS AND METHODS |
|---|
|
TOP
SUMMARY
INTRODUCTION
MATERIALS AND METHODS
RESULTS
DISCUSSION
REFERENCES |
|---|
). Fertilized eggs were collected with wet kitchen towel and
incubated at 28°C in a plastic dish.
Cloning of the G. bimaculatus homolog of byn
Total RNA was extracted from G. bimaculatus at various embryonic
stages using Isogen (Nippon-Gene). mRNA was isolated using an
OligotexTM-dT30 Super mRNA Purification Kit (TaKaRa). cDNA was
synthesized using the Superscript First Strand Synthesis Kit (Invitrogen). To
isolate a Gb'byn cDNA fragment by PCR, we used four primers
(see Fig. 1 for primer
position). The sequences of these guessmers were:
byn-5'A, 5'-ACNAAYGARATGATHGTNAC-3';
byn-5'B, 5'-GAYCCNRMNGCNATGTAYAC-3';
byn-3'A, 5'-AANGGRTTRTAYTTDATYTT-3'; and
byn-3'B, 5'-TCRTTYTGGTANGCNGTNAC-3'.
From the short fragment sequence obtained from the degenerate PCRs, we designed gene-specific primers and performed 5' and 3' rapid amplification of cDNA ends (RACE) using the SMART RACE cDNA Amplification Kit (Clontech). The following primers were used:
primary 3'RACE PCR, 5'-AACGCC GTCTACGTGCACCCCGAG-3';
nested 3'RACE PCR, 5'-CAACGGACAGATAATGCTTAACTC-3';
primary 5'RACE PCR, 5'-GAGTTAAGCATTATCTGTCCGTTG-3'; and
nested 5'RACE PCR, 5'-CCACTCGCCGTTCACGTACTTCCA-3'.
The Gb'byn cDNA sequence has been deposited in the DNA Data Bank of Japan (DDBJ) under Accession Number AB246318.
Embryo fixation, in situ hybridization and RNAi
Embryo fixation and in situ hybridization with a digoxigenin (DIG)-labeled
antisense RNA probe were performed as previously described
(Niwa et al., 2000;
Zhang et al., 2005). The dsRNA
used in parental and embryonic RNAi was in vitro transcribed from PCR
fragments amplified using primers containing T7 phage promoter sequences.
Sense and antisense RNA were synthesized using the MEGAscript Kit (Ambion).
The RNA was denatured in boiling water and then annealed at room temperature
overnight. The resulting dsRNA was ethanol precipitated and then resuspended
in water at a final concentration of 20 µM for Gb'byn
(309 bp), Gb'cad (426 bp) and DsRed2 (660 bp). In
all RNAi experiments, DsRed2 dsRNA was used as a negative control
(Miyawaki et al., 2004).
Injections for embryonic and parental RNAi were performed as previously
described (Zhang et al., 2002;
Mito et al., 2005). For
parental RNAi, the injected females were mated with untreated males, and eggs
were collected 5-10 days after injection.
|
RESULTS |
|---|
|
TOP
SUMMARY
INTRODUCTION
MATERIALS AND METHODS
RESULTS
DISCUSSION
REFERENCES |
|---|
Expression pattern of Gb'byn during early embryogenesis
Embryogenesis in Gryllus has been described previously
(Miyawaki et al., 2004;
Niwa et al., 1997;
Zhang et al., 2005). Briefly,
in terms of segmentation, the germ anlage is formed in the ventral side of the
posterior quarter of the egg by stage 3.0. Anterior segmentation occurs almost
simultaneously by stage 4.0, at least to the level of the segment polarity
genes, because Gryllus wingless (Gb'wg) is
expressed in five vertical stripes corresponding to the mandibular through
second thoracic segments. Then, the remaining posterior segments are
sequentially produced through germband elongation from the posterior growth
zone. The specification of the posterior segments can be tracked by the
appearance of Gb'wg stripes, which appear one by one in the
third thoracic segment at stage 4.3, and then in abdominal segment 1 at stage
4.4. At stage 7.5, the posterior-most stripe appears in abdominal segment
10.
We observed the expression pattern of Gb'byn during early embryogenesis by whole-mount in situ hybridization (Fig. 2). We were unable to detect any Gb'byn expression prior to stage 3.0 (data not shown). Gb'byn transcripts were first detected as two spots in the posterior terminal region of the embryo at stage 3.8 (Fig. 2A). Gb'byn expression appeared more strongly at stage 4.3 (Fig. 2B). During germband elongation, Gb'byn continued to be expressed in the terminal region of the embryo within the ectoderm, where the hindgut primordium is presumably located (Fig. 2C-E). The Gb'byn-expressing cells of the terminal region started to sink inward just after the completion of germband elongation and segmentation (Fig. 2F,G).
|
|
We have previously reported the expression pattern of
Gb'cad during early embryogenesis
(Shinmyo et al., 2005). Here,
we focused on its expression during late embryogenesis. At stage 9,
Gb'cad was expressed in a region adjacent to the hindgut
(Fig. 3E). At stage 11, the
expression domain was subdivided into two, corresponding to the Malpighian
tubules and developing posterior midgut
(Fig. 3F). In addition,
Gb'cad was expressed throughout late embryogenesis in the
cerci and in the region surrounding the orifice of the hindgut
(Fig. 3E,F). Double staining
indicated that the spatial patterns of Gb'cad and
Gb'byn expression were almost complementary to one another
in the posterior gut, i.e. in the posterior midgut, Malpighian tubules and
hindgut (Fig. 3G,H).
Gb'byn RNAi nymphs exhibited severe defects in the posterior gut
To examine the function of Gb'byn during Gryllus
embryogenesis, we used RNAi to deplete Gb'byn transcripts
and produce knockdown phenocopies. Two RNAi methods have been established in
Gryllus: embryonic RNAi (eRNAi)
(Miyawaki et al., 2004), which
involves microinjection of dsRNA into the early eggs; and parental RNAi
(pRNAi) (Mito et al., 2005),
which involves injection of dsRNA into adult virgin females to yield knockdown
phenocopies. We confirmed that no qualitative phenocopy differences were
produced when using eRNAi or pRNAi, and mainly used pRNAi for our analyses
because it does not produce any injection artefacts. As with the wild type,
eggs from the Gb'byn RNAi-injected females developed and
hatched nymphs 12-13 days after egg laying. No obvious difference was observed
in the cuticle patterns of wild-type and Gb'byn RNAi nymphs
(Fig. 4A,B). However, most
Gb'byn RNAi nymphs (95%, n=118 out of 124)
exhibited inhibited growth in the first instar and died before reaching the
second instar. To investigate the effects of Gb'byn
depletion on gut formation, we compared the morphology of the alimentary canal
in first-instar Gb'byn RNAi nymphs
(Fig. 4D,E) with that of the
wild type (Fig. 4C). The
alimentary canal of the wild-type nymph consists of the foregut, including
crop and proventriculus, the midgut, including gastric caecum and Malpighian
tubules, and the hindgut, including the small and large intestines and rectum
sac (Fig. 4C). The majority of
Gb'byn RNAi nymphs exhibited severe morphological defects in
the posterior gut (95%, n=38 out of 40;
Fig. 4D,E), whereas the crop
and proventriculus in the foregut, and the anterior region of the midgut,
including the gastric caecum, seemed to be formed normally. All affected
nymphs shared severe defects in the hindgut and posterior region of the
midgut, whereas the severity of the disruption of the Malpighian tubules
varied. In most of the affected Gb'byn RNAi nymphs (74%,
n=28 out of 38; Fig.
4D), the tubules were much shorter than those of the wild type
(Fig. 4C). In the most strongly
affected nymphs, the tubules were virtually absent (26%, n=10 out of
38; Fig. 4E). Thus,
Gb'byn RNAi nymphs that lack the posterior gut seem unable
to absorb food, or to resorb water and ions, resulting in starvation in the
first instar. These results indicate that Gb'byn is required
for the formation of the posterior gut, but not for posterior elongation and
segmentation.
|
Although Gb'hh expression is observed in the terminal
region during germband elongation
(Miyawaki et al., 2004),
overlapping with Gb'byn expression, Gb'hh
expression patterns were unaffected in the Gb'byn RNAi
embryos (data not shown). During invagination of the proctodeum in wild-type
embryos, Gb'hh is expressed in the developing hindgut
(Inoue et al., 2002). At stage
11-12, the expression domain became subdivided into three regions: strong
expression in the small intestine and rectum sac, and weak expression in the
large intestine (Fig. 5E)
(Inoue et al., 2002). In the
Gb'byn RNAi embryos, abnormal expression of
Gb'hh was observed in the hindgut remnant, probably as a
combined pattern of the small intestine and rectum sac expression domains,
with reductions in both (100%, n=25;
Fig. 5F). This indicates a
dramatic defect in the large intestine. In addition, Gb'hh
expression in the Malpighian tubules was also disrupted in the
Gb'byn RNAi embryos (Fig.
5F).
Gb'wg is expressed in the posterior growth zone during
germband elongation (Miyawaki et al.,
2004). This expression pattern was unaffected in the
Gb'byn RNAi embryos (data not shown). In the wild-type
embryos at stage 11-12, Gb'wg expression was detected in two
regions, the anterior region of the small intestine and the posterior rectum
of the hindgut (Fig. 5G)
(Inoue et al., 2002). In the
Gb'byn RNAi embryos, Gb'wg expression was
detected in both anterior and posterior regions of the severely reduced
hindgut, with reduced expression domains (92%, n=23 out of 25;
Fig. 5H). This result indicates
a dramatic defect in the large intestine of Gb'byn RNAi
embryos, as well as relatively mild defects in the small intestine and rectum,
consistent with the pattern of Gb'hh expression in the
Gb'byn RNAi embryos.
Gb'cad is expressed in the posterior growth zone during
germband elongation (Shinmyo et al.,
2005). This expression pattern was unaffected in
Gb'byn RNAi embryos (data not shown). In wild-type embryos
at stage 9, Gb'cad was expressed in the region surrounding
the orifice of the hindgut and in the region adjacent to the hindgut
(Fig. 3E,
Fig. 5I).
Gb'cad expression in both domains was greatly reduced in the
Gb'byn RNAi embryos (100%, n=10;
Fig. 5J). Additional domains of
Gb'cad expression in the cerci were not affected in the
Gb'byn RNAi embryos (Fig.
5, compare I with J). At stages 11-12, Gb'cad
expression was detected in the region surrounding the orifice of the hindgut,
the Malpighian tubules and the posterior midgut in wild-type embryos
(Fig. 3F,
Fig. 5K).
Gb'cad expression in the region surrounding the orifice of
the hindgut and posterior midgut was greatly reduced in the
Gb'byn RNAi embryos (88%, n=22 out of 25;
Fig. 5L), indicating a
reduction in these structures. We also found that Gb'cad was
weakly expressed in the very small remnant of the Malpighian tubules seen in
all Gb'byn RNAi embryos (100%, n=25;
Fig. 5L), indicating that the
primordium of the Malpighian tubules was formed in Gb'byn
RNAi embryos. This suggests that the disruption of the Malpighian tubules
observed in the Gb'byn RNAi nymphs
(Fig. 4D,E) resulted from an
inhibition of tubule elongation. This interpretation is supported by the fact
that the shortened Malpighian tubules were formed in most
Gb'byn RNAi nymphs (Fig.
4D). Thus, in Gb'byn RNAi embryos, the
expression patterns of the marker genes for the posterior gut suggest that
Gb'byn is necessary for differentiation of the posterior
midgut and hindgut, and for elongation of the Malpighian tubules.
|
). Although it has been shown that cad is required
for the formation of all trunk segments in short- and intermediate-germband
insects (Copf et al., 2004;
Shinmyo et al., 2005), the
role of cad in posterior terminal patterning in these insects has not
been investigated. To determine Gb'cad function in
Gryllus, we generated embryos depleted of Gb'cad by
pRNAi, and examined the expression patterns of Gb'byn during
Gb'cad RNAi embryogenesis. First, we confirmed that most
Gb'cad RNAi embryos obtained by pRNAi exhibited severe
defects in the trunk segments (Fig.
6A-C), as described previously in Gb'cad eRNAi
experiments (Shinmyo et al.,
2005). In wild-type embryos at stage 4, Gb'byn
was expressed in the posterior terminal region
(Fig. 6D), and this remained
unaffected in Gb'cad RNAi embryos (100%, n=10;
Fig. 6E). This suggests that
Gb'cad is not involved in establishing the hindgut
primordium. In wild-type embryos, Gb'byn-expressing cells in
the terminal region sink inwards at stage 7.5 and are completely internalized
by stage 9 (Fig. 3C,
Fig. 6F). In the
Gb'cad RNAi embryos, the Gb'byn-expressing
cells failed to invaginate at stage 9, remaining on the outside of the embryo
(Fig. 6G,H). We also examined the expression pattern of Gb'hh, which is also used as a marker gene for the hindgut (Fig. 6I). In the Gb'cad RNAi embryos, Gb'hh expression was observed in the external hindgut remnant (Fig. 6J,K). These observations indicate that the invagination of the hindgut primordium did not occur in the Gb'cad RNAi embryos, suggesting that Gb'cad is not necessary to establish the hindgut primordium, but is required for internalization of the primordium. However, we cannot rule out the possibility that the hindgut primordium, in which Gb'byn is normally expressed, is not correctly specified in the Gb'cad RNAi embryos. In this case, Gb'cad and Gb'byn would be activated independently in the hindgut primordium, and both genes would be necessary for the establishment of the hindgut primordium. Further expression analyses of hindgut markers in Gb'cad RNAi embryos will be required to determine Gb'cad function in specification of the hindgut primordium.
|
DISCUSSION |
|---|
|
TOP
SUMMARY
INTRODUCTION
MATERIALS AND METHODS
RESULTS
DISCUSSION
REFERENCES |
|---|
Specification of the hindgut primordium appears to occur independently of posterior segment specification in Gryllus
In Drosophila, all segments and posterior terminal structures are
specified by the blastoderm stage. By contrast, in Gryllus, posterior
segments are specified in an anterior to posterior direction through
elongation of the posterior growth zone, and invagination of the posterior gut
starts after the specification of the posterior segments. It is not clear how
and when the posterior segments and terminal structures are specified, or how
developmental timing of their structures is controlled during Gryllus
embryogenesis. We found that Gb'byn is expressed as two
spots in the posterior terminal cells of embryos, where the hindgut primordium
is presumably located, before AP axial elongation
(Fig. 2A). This suggests that
the specification of the hindgut primordium occurs before AP axial elongation,
and independently of posterior segment specification. This interpretation is
supported by our previous data indicating that the terminal structures, such
as the hindgut and cerci, are formed in Gb'hb or
Gb'krüppel RNAi embryos, in which posterior segments
generated from the growth zone are severely defective
(Mito et al., 2005;
Mito et al., 2006). Further
support comes from studies showing that in Gryllus embryos subjected
to lethal doses of radiation, the most posterior segment carrying the cerci is
always present, even if many other segments are missing
(Sander, 1976).
|
It is important to note that tailless, which acts upstream of
byn in Drosophila terminal patterning, is already expressed
at the blastoderm stage at the posterior pole of Tribolium embryos.
This suggests that there is a group of cells within the posterior growth zone
that is determined at the blastoderm stage to produce the terminal structures
in Tribolium (Schröder et
al., 2000). This conceivably might also apply to Gryllus
embryogenesis.
Roles of Cdx/cad and Bra/byn in posterior gut patterning
We found that the posterior gut, consisting of the posterior midgut,
Malpighian tubules and hindgut, was severely reduced in
Gb'byn RNAi nymphs (Fig.
4, Fig. 7A).
Furthermore, detailed analysis of the expression patterns of tissue-specific
markers revealed that Gb'byn is necessary for
differentiation of the midgut and hindgut, and for elongation of the
Malpighian tubules (Fig. 5,
Fig. 7A). In Drosophila
byn mutants, the posterior gut is severely reduced as a consequence of
massive apoptosis in the gut primordia
(Kispert et al., 1994;
Singer et al., 1996). It
remains unclear whether apoptosis contributes to the reduced posterior gut in
Gb'byn RNAi embryos because of a technical problem
associated with the TUNEL staining. However, the similarities in phenotype
suggest that byn function during embryogenesis is highly conserved
between long- and intermediate-germband insects. Bra is not reported
to be involved in gut formation in vertebrates, but it is expressed in the
posterior gut endoderm of hemichordates
(Peterson et al., 1999) and
echinoderms (Gross and McClay,
2001; Shoguchi et al.,
1999). Although the posterior gut endoderm of these animals is
substantially different from the hindgut ectoderm of insects, these
similarities suggest that the involvement of Bra/byn in specification
of the posterior gut might be ancestral to bilaterians. A similar presumption
might also extend to the role of Cdx/cad in gut development. In
Gryllus, Gb'cad is expressed in the Malpighian tubules and
posterior midgut endoderm during late embryogenesis
(Fig. 2). Our RNAi analysis
shows that Gb'cad is necessary for internalization of the
posterior gut primordium (Fig.
6). In Drosophila, Dm'cad is known to be
expressed in the Malpighian tubules and posterior midgut endoderm of older
embryos (Macdonald and Struhl,
1986; Mlodzik et al.,
1985), and to be essential for internalization and maintenance of
the posterior gut primordium (Wu and
Lengyel, 1998). Thus, the expression pattern and function of
cad in posterior gut development are highly conserved between
Gryllus and Drosophila. In vertebrates, Cdx genes
are expressed in the gut endoderm during late embryogenesis (reviewed by
Freund et al., 1998), and
Cdx2 mutant mice develop intestinal tumors
(Chawengsaksophak et al.,
1997). In Caenorhabditis elegans, the cad
homolog pal-1 is expressed zygotically in mesoderm cells of the
posterior gut (Edgar et al.,
2001). On the basis of these data, we hypothesize that the
involvement of Cdx/cad and Bra/byn in the specification of
the posterior gut might be an ancestral feature of bilaterians.
|
|
),
suggesting conservation in the mechanisms of terminal patterning.
Evolution of Cdx/cad and Bra/byn function in AP axial elongation
The progressive growth of AP axial structures from a posterior region is
observed in such diverse animals as chordates, short- and
intermediate-germband arthropods, annelids and molluscs. In short- and
intermediate-germband arthropods, posterior segments are sequentially produced
from the posterior growth zone, where cad is expressed
(Copf et al., 2003;
Dearden and Akam, 2001;
Schulz et al., 1998;
Shinmyo et al., 2005)
(Fig. 7B) and required for AP
axial elongation from the growth zone (Copf
et al., 2004; Shinmyo et al.,
2005). cad expression in the growth zone is likely to be
regulated by Wg/Arm signaling in Gryllus embryos
(Shinmyo et al., 2005)
(Fig. 7B). Segmentation in
short- and intermediate-germband arthropods resembles somitogenesis in
vertebrates, in which somites are generated progressively from a posteriorly
located presomitic zone (reviewed by Peel
et al., 2005). In addition, the Cdx genes, which are
regulated by Wnt signaling, are expressed in the nascent mesoderm of the
primitive streak (Ikeya and Takada,
2001; Marom et al.,
1997; Meyer and Gruss,
1993) (Fig. 7B),
and are involved in axial elongation and somitogenesis
(Epstein et al., 1997;
Subramanian et al., 1995;
van den Akker et al., 2002).
These similarities suggest that the molecular mechanisms underlying these
processes are conserved between short- and intermediate-germband arthropods
and vertebrates. Recently, it has been shown that even-skipped
(eve) is expressed in the posterior growth zone and is required for
AP axial elongation in the intermediate-germband insect Oncopeltus
fasciatus (Liu and Kaufman,
2005). This fact may also suggest conserved mechanisms for these
processes because, in vertebrates, Evx1 (the eve homolog) is
known to be expressed in the primitive streak and tail bud, although its
function has not been investigated (Dush
and Martin, 1992). These data suggest that AP axial formation from
the posterior growth zone is ancestral to bilaterians. A similar hypothesis
has been proposed, based on a comparison of Bra expression patterns
in molluscs and vertebrates. In vertebrates, Bra is also expressed in
the nascent mesoderm of the primitive streak and tail bud
(Kispert and Herrmann, 1994;
Knezevic et al., 1997;
Wilkinson et al., 1990)
(Fig. 7B), and is necessary for
AP axial formation (Wilson and Beddington,
1997). Because Bra expression in the posterior pole of
the AP axis, up to the end of mollusc larval development, is similar to that
in vertebrates, Lartillot et al.
(Lartillot et al., 2002) have
proposed that Bra might have a conserved role in the regulation of AP
patterning among bilaterians, through maintenance of the posterior growth
zone. This hypothesis implies that the role of Bra/byn in AP axial
elongation might be ancestral to bilaterians. Importantly, we found that
Gb'byn is expressed exclusively in the posterior terminal region
(Fig. 7B), and is not involved
in AP axial elongation from the growth zone. Therefore, if the hypothesis is
correct, our results suggest that the function of Bra/byn in
AP axial elongation might have been lost in insects. More data from a wider
range of protostomes will be required to confirm this.
|
ACKNOWLEDGMENTS |
|---|
|
Footnotes |
|---|
Present address: Division of Genetic Information, Institute for Genome
Research, The University of Tokushima, Tokushima 770-8503, Japan
|
REFERENCES |
|---|
|
TOP
SUMMARY
INTRODUCTION
MATERIALS AND METHODS
RESULTS
DISCUSSION
REFERENCES |
|---|
Chawengsaksophak, K., James, R., Hammond, V. E., Kontgen, F. and
Beck, F. (1997). Homeosis and intestinal tumours in
Cdx2 mutant mice. Nature
386, 84-87.[CrossRef][Medline]
Copf, T., Rabet, N., Celniker, S. E. and Averof, M.
(2003). Posterior patterning genes and the identification of a
unique body region in the brine shrimp Artemia franciscana.Development 130,5915
-5927.
Copf, T., Schröder, R. and Averof, M.
(2004). Ancestral role of caudal genes in axis
elongation and segmentation. Proc. Natl. Acad. Sci.
USA 101,17711
-17715.
Davis, G. K. and Patel, N. H. (2002). Short,
long, and beyond: molecular and embryological approaches to insect
segmentation. Annu. Rev. Entomol.
47,669
-699.[CrossRef][Medline]
Dearden, P. K. and Akam, M. (2001). Early
embryo patterning in the grasshopper, Schistocerca gregaria:
wingless, decapentaplegic and caudal expression.
Development 128,3435
-3444.
Dush, M. K. and Martin, G. R. (1992). Analysis
of mouse Evx genes: Evx-1 displays graded expression in the
primitive streak. Dev. Biol.
151,273
-287.[CrossRef][Medline]
Edgar, L. G., Carr, S., Wang, H. and Wood, W. B.
(2001). Zygotic expression of the caudal homolog
pal-1 is required for posterior patterning in Caenorhabditis
elegans embryogenesis. Dev. Biol.
229, 71-88.[CrossRef][Medline]
Epstein, M., Pillemer, G., Yelin, R., Yisraeli, J. K. and
Fainsod, A. (1997). Patterning of the embryo along the
anterior-posterior axis: the role of the caudal genes.
Development 124,3805
-3814.[Abstract]
Freund, J. N., Domon-Dell, C., Kedinger, M. and Duluc, I.
(1998). The Cdx-1 and Cdx-2 homeobox genes in
the intestine. Biochem. Cell Biol.
76,957
-969.[CrossRef][Medline]
Gross, J. M. and McClay, D. R. (2001). The role
of Brachyury (T) during gastrulation movements in the sea urchin
Lytechinus variegatus. Dev. Biol.
239,132
-147.[CrossRef][Medline]
Herrmann, B. G. (1991). Expression pattern of
the Brachyury gene in whole-mount TWis/TWis mutant embryos.
Development 113,913
-917.[Abstract]
Hoch, M. and Pankratz, M. J. (1996). Control of
gut development by fork head and cell signaling molecules in Drosophila.Mech. Dev. 58,3
-14.[CrossRef][Medline]
Ikeya, M. and Takada, S. (2001). Wnt-3a is
required for somite specification along the anteroposterior axis of the mouse
embryo and for regulation of cdx-1 expression. Mech.
Dev. 103,27
-33.[CrossRef][Medline]
Inoue, Y., Niwa, N., Mito, T., Ohuchi, H., Yoshioka, H. and
Noji, S. (2002). Expression patterns of hedgehog,
wingless, and decapentaplegic during gut formation of
Gryllus bimaculatus (cricket). Mech. Dev.
110,245
-248.[CrossRef][Medline]
Kispert, A. and Herrmann, B. G. (1994).
Immunohistochemical analysis of the Brachyury protein in wild-type and mutant
mouse embryos. Dev. Biol.
161,179
-193.[CrossRef][Medline]
Kispert, A., Herrmann, B. G., Leptin, M. and Reuter, R.
(1994). Homologs of the mouse Brachyury gene are
involved in the specification of posterior terminal structures in
Drosophila, Tribolium, and Locusta. Genes
Dev. 8,2137
-2150.
Kispert, A., Ortner, H., Cooke, J. and Herrmann, B. G.
(1995). The chick Brachyury gene: developmental
expression pattern and response to axial induction by localized activin.
Dev. Biol. 168,406
-415.[CrossRef][Medline]
Knezevic, V., De Santo, R. and Mackem, S.
(1997). Two novel chick T-box genes related to mouse
Brachyury are expressed in different, non-overlapping mesodermal
domains during gastrulation. Development
124,411
-419.[Abstract]
Kusch, T. and Reuter, R. (1999). Functions for
Drosophila brachyenteron and forkhead in mesoderm
specification and cell signalling. Development
126,3991
-4003.[Abstract]
Lartillot, N., Lespinet, O., Vervoort, M. and Adoutte, A.
(2002). Expression pattern of Brachyury in the mollusc
Patella vulgata suggests a conserved role in the establishment of the AP axis
in Bilateria. Development
129,1411
-1421.
Liu, P. Z. and Kaufman, T. C. (2004).
hunchback is required for suppression of abdominal identity, and for
proper germband growth and segmentation in the intermediate germband insect
Oncopeltus fasciatus. Development
131,1515
-1527.
Liu, P. Z. and Kaufman, T. C. (2005).
even-skipped is not a pair-rule gene but has segmental and gap-like
functions in Oncopeltus fasciatus, an intermediate germband insect.
Development 132,2081
-2092.
Liu, P., Wakamiya, M., Shea, M. J., Albrecht, U., Behringer, R.
R. and Bradley, A. (1999). Requirement for Wnt3 in vertebrate
axis formation. Nat. Genet.
22,361
-365.[CrossRef][Medline]
Macdonald, P. M. and Struhl, G. (1986). A
molecular gradient in early Drosophila embryos and its role in
specifying the body pattern. Nature
324,537
-545.[CrossRef][Medline]
Marom, K., Shapira, E. and Fainsod, A. (1997).
The chicken caudal genes establish an anterior-posterior gradient by
partially overlapping temporal and spatial patterns of expression.
Mech. Dev. 64,41
-52.[CrossRef][Medline]
Melby, A. E., Warga, R. M. and Kimmel, C. B.
(1996). Specification of cell fates at the dorsal margin of the
zebrafish gastrula. Development
122,2225
-2237.[Abstract]
Meyer, B. I. and Gruss, P. (1993). Mouse
Cdx-1 expression during gastrulation.
Development 117,191
-203.
Mito, T., Sarashina, I., Zhang, H., Iwahashi, A., Okamoto, H.,
Miyawaki, K., Shinmyo, Y., Ohuchi, H. and Noji, S. (2005).
Non-canonical functions of hunchback in segment patterning of the
intermediate germ cricket Gryllus bimaculatus.Development 132,2069
-2079.
Mito, T., Okamoto, H., Shinahara, W., Shinmyo, Y., Miyawaki, K.,
Ohuchi, H. and Noji, S. (2006). Krüppel acts as
a gap gene regulating expression of hunchback and
even-skipped in the intermediate germ cricket Gryllus
bimaculatus. Dev. Biol. 294,471
-481.[CrossRef][Medline]
Miyawaki, K., Mito, T., Sarashina, I., Zhang, H., Shinmyo, Y.,
Ohuchi, H. and Noji, S. (2004). Involvement of
Wingless/Armadillo signaling in the posterior sequential segmentation in the
cricket, Gryllus bimaculatus (Orthoptera), as revealed by RNAi
analysis. Mech. Dev.
121,119
-130.[CrossRef][Medline]
Mlodzik, M., Fjose, A. and Gehring, W. J.
(1985). Isolation of the caudal, a Drosophila
homeobox-containing gene with maternal expression, whose transcripts form a
concentration gradient at the pre-blastoderm stage. EMBO
J. 4,2961
-2969.[Medline]
Niwa, N., Saito, M., Ohuchi, H., Yoshioka, H. and Noji, S.
(1997). Correlation between Distal-less expression patterns and
structures of appendages in the development of the two-spotted cricket,
Gryllus bimaculatus. Zool. Sci.
14,115
-125.
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]
Peel, A. D., Chipman, A. D. and Akam, M.
(2005). Arthropod segmentation: beyond the Drosophila
paradigm. Nat. Rev. Genet.
6, 905-916.[CrossRef][Medline]
Peterson, K. J., Cameron, R. A., Tagawa, K., Satoh, N. and
Davidson, E. H. (1999). A comparative molecular approach to
mesodermal patterning in basal deuterostomes: the expression pattern of
Brachyury in the enteropneust hemichordate Ptychodera flava.Development 126,85
-95.[Abstract]
Sander, K. (1976). Specification of the basic
body pattern in insect embryogenesis. Adv. Insect
Physiol. 12,125
-238.
Schoppmeier, M. and Schröder, R. (2005).
Maternal Torso signaling controls body axis elongation in a short germ insect.
Curr. Biol. 15,2131
-2136.[CrossRef][Medline]
Schröder, R., Eckert, C., Wolff, C. and Tautz, D.
(2000). Conserved and divergent aspects of terminal patterning in
the beetle Tribolium castaneum. Proc. Natl. Acad. Sci.
USA 97,6591
-6596.
Schulte-Merker, S., Ho, R. K., Herrmann, B. G. and
Nusslein-Volhard, C. (1992). The protein product of the
zebrafish homologue of the mouse T gene is expressed in nuclei of the
germ ring and the notochord of the early embryo.
Development 116,1021
-1032.[Abstract]
Schulte-Merker, S., van Eeden, F. J., Halpern, M. E., Kimmel, C.
B. and Nusslein-Volhard, C. (1994). no tail
(ntl) is the zebrafish homologue of the mouse T
(Brachyury) gene. Development
120,1009
-1015.[Abstract]
Schulz, C., Schröder, R., Hausdorf, B., Wolff, C. and
Tautz, D. (1998). A caudal homologue in the short
germ band beetle Tribolium shows similarities to both, the
Drosophila and the vertebrate caudal expression patterns.
Dev. Genes Evol. 208,283
-289.[CrossRef][Medline]
Shinmyo, Y., Mito, T., Matsushita, T., Sarashina, I., Miyawaki,
K., Ohuchi, H. and Noji, S. (2005). caudal is
required for gnathal and thoracic patterning and for posterior elongation in
the intermediate-germband cricket Gryllus bimaculatus. Mech.
Dev. 122,231
-239.[CrossRef][Medline]
Shoguchi, E., Satoh, N. and Maruyama, Y. K.
(1999). Pattern of Brachyury gene expression in starfish
embryos resembles that of hemichordate embryos but not of sea urchin embryos.
Mech. Dev. 82,185
-189.[CrossRef][Medline]
Singer, J. B., Harbecke, R., Kusch, T., Reuter, R. and Lengyel,
J. A. (1996). Drosophila brachyenteron regulates
gene activity and morphogenesis in the gut.
Development 122,3707
-3718.[Abstract]
Smith, J. C., Price, B. M., Green, J. B., Weigel, D. and
Herrmann, B. G. (1991). Expression of a Xenopus
homolog of Brachyury (T) is an immediate-early response to
mesoderm induction. Cell
67, 79-87.[CrossRef][Medline]
Subramanian, V., Meyer, B. I. and Gruss, P.
(1995). Disruption of the murine homeobox gene Cdx1
affects axial skeletal identities by altering the mesodermal expression
domains of Hox genes. Cell
83,641
-653.[CrossRef][Medline]
van den Akker, E., Forlani, S., Chawengsaksophak, K., de Graaff,
W., Beck, F., Meyer, B. I. and Deschamps, J. (2002).
Cdx1 and Cdx2 have overlapping functions in anteroposterior
patterning and posterior axis elongation. Development
129,2181
-2193.
Wilkinson, D. G., Bhatt, S. and Herrmann, B. G.
(1990). Expression pattern of the mouse T gene and its
role in mesoderm formation. Nature
343,657
-659.[CrossRef][Medline]
Wilson, V. and Beddington, R. (1997).
Expression of T protein in the primitive streak is necessary and sufficient
for posterior mesoderm movement and somite differentiation. Dev.
Biol. 192,45
-58.[CrossRef][Medline]
Wilson, V., Manson, L., Skarnes, W. C. and Beddington, R. S.
(1995). The T gene is necessary for normal mesodermal
morphogenetic cell movements during gastrulation.
Development 121,877
-886.[Abstract]
Wu, L. H. and Lengyel, J. A. (1998). Role of
caudal in hindgut specification and gastrulation suggests homology
between Drosophila amnioproctodeal invagination and vertebrate
blastopore. Development
125,2433
-2442.[Abstract]
Zhang, H., Shinmyo, Y., Hirose, A., Mito, T., Inoue, Y., Ohuchi,
H., Loukeris, T. G., Eggleston, P. and Noji, S. (2002).
Extrachromosomal transposition of the transposable element Minos in
embryos of the cricket Gryllus bimaculatus. Dev. Growth
Differ. 44,409
-417.[CrossRef][Medline]
Zhang, H., Shinmyo, Y., Mito, T., Miyawaki, K., Sarashina, I.,
Ohuchi, H. and Noji, S. (2005). Expression patterns of the
homeotic genes Scr, Antp, Ubx, and abd-A during
embryogenesis of the cricket Gryllus bimaculatus. Gene Expr.
Patterns 5,491
-502.[Medline]
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati 
Twitter What's this?
This article has been cited by other articles:
|
|
 |
|
  T. Mito and S. Noji The Two-Spotted Cricket Gryllus bimaculatus: An Emerging Model for Developmental and Regeneration Studies CSH Protocols, December 1, 2008; 2008(13): pdb.emo110 - pdb.emo110. [Abstract] [Full Text]
|
|
|
|
 |
|
 H. Sugawara, O. Ogasawara, K. Okubo, T. Gojobori, and Y. Tateno DDBJ with new system and face Nucleic Acids Res., January 11, 2008; 36(suppl_1): D22 - D24. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
