While significant progress has been made in the understanding of the molecular mechanisms by which organ identity is specified in developing flowers, much less is known about the mechanisms of cell fate specification within individual organs. A molecular genetic approach was chosen to elucidate how cell fate is specified in the carpel, initially focusing on the role of CRABS CLAW. It has recently been shown that CRABS CLAW is required for the specification of abaxial cell fate in the carpels. This conclusion was based on genetic analyses of both loss- and gain-of-function alleles of CRABS CLAW as well as comparisons with closely related gene family members.
The development of adaxial tissues in abaxial positions in the carpel requires two conditions: first, the loss of abaxial cell fate, and second, the loss of suppression of genes promoting meristematic growth. The second condition must be met in order to allow the development of placental meristems on the abaxial surfaces of the carpel. This proposal is focused on two genes, CRABS CLAW and KANADI, that appear to act independently in a partially redundant manner to promote the specification of abaxial cell fate in the medial regions of the carpel. While single mutants in either gene do not display a loss of polar differentiation in the carpel, in crabs claw kanadi double mutants mirror image duplications of adaxial tissues develop in abaxial positions of the carpel.
The overall aims of this proposal are to identify and characterize genes and phytohormones that play a role in either specification of abaxial cell fate or suppression and/or activation of meristematic potential
