Molecular Genetics of the Yabby Gene Family

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0077984BowmanMost lateral organs of vascular plants are polar in nature, exhibiting asymmetries in both their proximo-distal and abaxial-adaxial (dorso-ventral or top of the leaf versus the bottom of the leaf) axes. For example, in angiosperm leaves these asymmetries are often manifested as a broad distal blade and a narrower proximal petiole in the proximo-distal axis and differences in the morphology and distribution of cell types in the abaxial-adaxial axis. This proposal is focused on the establishment of abaxial-adaxial polarity in lateral organs. Specifically, a molecular genetic approach to elucidate how cell fate is specified in the abaxial regions of lateral organs will be focused on the roles of members of the YABBY gene family. It has been shown that CRC, the founding member of the family, is required for the specification of abaxial cell fate in the carpels, and that other members of the YABBY gene family promote abaxial cell fate in all lateral organs produced from the apical meristem. This conclusion was based on genetic analyses of both loss and gain of function alleles of CRC and gain of function alleles of other members of the YABBY gene family.The aims of the present proposal are three fold. First, four members of the YABBY gene family whose functions appear to contribute to the specification of abaxial cell fate in lateral organs, will be characterized specifically assessing the shared and unique functions of members of the gene family. Second, experiments aimed at elucidating the genetic relationships between members of the YABBY gene family and genes that promote adaxial cell fates and other genes that promote abaxial cell fate will be undertaken. Third, the ability to manipulate polarity in lateral organs should allow an assessment of interactions between lateral organs and the meristems from which they are derived. In particular, the effect of lateral organs consisting entirely of abaxial fates on the fate of the apical meristem will be followed. These experiments should lead to a better understanding of how polarity is established and maintained in developing lateral organs.