Biology Reference
In-Depth Information
In addition, in the backpetals mutant in A.majus, the ectopic expression of
CYC in the lateral and ventral positions results in a dorsalized corolla. However, it
seems likely that the androecial development is not affected by the ectopic expres-
sion of CYC because the two lateral and two ventral stamens are still fertile [5,26].
In the actinomorphic flower of legume Cadia, no LegCYC1B mRNA is detected
in stamens [27]. It is hard to determine whether LegCYC1B or other CYC homo-
logues in legumes have a role in controlling androecial development from data to
date [13,14,21]. RAY2 in Senecio and GhCYC2 in Gerbera (Asteraceae) mainly
promote the growth of the ligule (the ventral petals) in ray florets and are excluded
from the dorsal rudimentary petals [17,18]. In Veronica and Gratiola (Scrophula-
riaceae s.l.), some of CYC-like genes have dorsal-specific expressions while some
have lost this feature, but their expressions do not correlate with ventral stamen
arrest [21]. Therefore, expression data correlated with the ventral stamen abortion
have not been reported yet for members of the ECE-CYC2 clade. It is uncertain
whether abortion of the ventral stamens is related to CYC-like gene activities or
to the effect of an unknown analogous counterpart of CYC-like genes, such as
members of ECE-CYC3 clade or other factors [3,12,20].
The family Gesneriaceae is sister to the remainder of Lamiales s.l. [28] and
has diverse forms of zygomorphy relating to the floral organ differentiation early
in the order [1,2,24]. In Gesneriaceae, Opithandra exhibits a peculiar floral mor-
phology, where only the two lateral stamens are fertile and both the dorsal and
ventral stamens are aborted in the third whorl (Figure 1). Phylogenetic analyses
suggest that the floral morphology of Opithandra is likely derived from a weakly
Figure 1.
Flower morphology of Opithandra dinghushanensis.
A) Inflorescence
with flowers near or at anthesis, showing strongly zygomorphic corolla; B) An opened corolla
at anthesis showing two dorsal petals smaller than two lateral and one ventral petals, and androecium with two
fertile lateral stamens and two ventral and one dorsal staminodes; C) Magnification of the framed part in (B),
showing two infertile lateral stamens with short filaments and small sterile anthers, and a tiny dorsal staminode
that is barely visible; D) Floral diagram; Scale bars, 10 mm (A), 7 mm (B) and 3 mm (C). dp, dorsal petal (in
blue); dt, dorsal staminode; lp, lateral petal (in yellow); lt, lateral stamen (in yellow); s, sepal; vp, ventral petal (in
pink); vt, ventral staminode (in pink).
