|Flower Meristem Identity|
Identity Genes can be divided into two distinct classes.
|In general, mutations in meristem identity genes such as LFY and AP1 lead to a partial conversion of flowers into shoots, whereas mutations in TFL cause both early flowering and premature conversion of the normally indeterminate shoot meristem into a flower meristem, with the resulting formation of a terminal flower. TFL can be considered a negative spatial regulator of both LFY and AP1, since mutations in TFL lead to ectopic activity of both LFY and AP1 and the tfl phenotype can be largely suppressed if both the LFY and AP1 genes are inactivated. Although lfy and ap1 mutants display partial conversion of flowers into shoots, this phenotype is dramatically enhanced in lfy ap1 double mutants such that a nearly complete conversion of flowers into shoots occurs.|
A. lfy flower
B. lfy inflorescence
C. ap1 flower
D. lfy ap1 inflorescence
E. tfl flower & whole plant
|Additionally, LFY and AP1 are each sufficient to promote flower initiation, since ectopic expression of either gene from the CaMV35S promoter largely replaces shoots with individual flowers.|
|The role of the CAL gene largely overlaps with that of AP1, such that cal single mutants are not significantly different from wild-type, whereas mutations in the CAL gene dramatically enhance the phenotype of ap1 mutants causing a massive proliferation of "inflorescence-like' meristems in place of flowers.||
ap1cal double mutant
|The phenotypes conferred by
mutations in meristem identity genes are sensitive to environmental factors such as
temperature and day length. For example, short days or low temperatures, which attenuate
floral induction, enhance the phenotype of flower meristem identity mutants but suppress
the phenotype of tfl mutants.
Thanks to Detlef Weigel for the lfy and ap1 lfy mutant photos.
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