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Fig. 2. Differential effect of PIN1 and PGP19 overexpression in
Arabidopsis seedlings. (A,B) Immunolocalization of
PIN1 in the XVE-PIN1 line without (A) and with estradiol (B)
induction. Ectopically expressed PIN1 localizes to the basal (lower) side of
epidermal cells (arrowheads). (C,D) Immunolocalization of
DEX-induced PGP19-HA in GVG-PGP19-HA (C) and PGP1-myc in
GVG-PGP1-myc (D) lines show non-polar localization in epidermal cells.
(E-H) Differential effects of PIN1, PGP19-HA and PGP1-myc
overexpression on seedling development. Non-induced control (E); reduced root
length and gravitropic response by induced PIN1 expression (F); no dramatic
phenotypes caused by induced PGP19-HA (G) and PGP1-myc (H)
expression, apart from a reduction in cotyledon outgrowth in the DEX-treated
GVG-PGP19-HA line (G). (I-K) PIN1 overexpression phenotypes in
dark-grown seedlings: straight hypocotyls in untreated controls (I); hypocotyl
twists in estradiol-treated seedlings (J); this phenotype is almost completely
reversed by the auxin transport inhibitor NPA (K). (L-O) Changes in the
DR5::GUS auxin response reporter expression after PIN1
overexpression: DR5::GUS is weakly and equally expressed in
hypocotyls of dark-grown seedlings (L), but shows randomly distributed local
maxima that correlate with unequal cell elongation after PIN1 induction (M);
GUS signal in the root tip is confined to the columella in the non-induced
control (N), but increases and extends to the lateral root cup after PIN1
induction (O). (P,Q) Reduction of DR5rev::GFP signal in
the columella after PGP19-HA expression (Q) when compared with untreated
controls (P). (R) Concentration-dependent effect of estradiol-induced
PIN1 overexpression on root elongation and gravitropism (calculated as
vertical growth index (VGI) (Grabov et
al., 2005). (S) Hypocotyl twisting and inhibition of root
length following PIN overexpression can be reversed by NPA. (T)
PGP1-myc and PGP19-HA overexpression have no pronounced effects on
root growth, hypocotyl growth in the dark or sensitivity to NPA. Scale bars: 3
mm. Error bars represent s.e.m., n=20.
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