Molecular Genetic Characterization of Pathways Involved in Establishing Abaxial Cell Fate in Arabidopsis Carpels

虽然在了解花发育过程中器官身份指定的分子机制方面取得了重大进展，但对单个器官内细胞命运指定的机制知之甚少。我们选择了一种分子遗传学的方法来阐明细胞命运是如何在心皮中被指定的，最初的重点是螃蟹爪的作用。最近的研究表明，螃蟹爪对心皮中背轴细胞命运的规定是必需的。这一结论是基于对蟹爪的功能缺失和功能获得等位基因的遗传分析以及与近缘基因家族成员的比较。心皮背面近轴组织的发育需要两个条件：一是失去了背面细胞的命运，二是失去了促进分生组织生长的抑制基因。第二个条件必须满足，才能使心皮背面的胎盘分生组织发育。本研究的重点是两个基因，螃蟹爪和KANADI，它们似乎以部分冗余的方式独立作用，促进心皮内侧区域的下轴细胞命运的规范。虽然这两种基因的单突变体在心皮中都不会表现出极性分化的丧失，但在蟹爪kanadi中，双突变体在心皮的背面位置出现了近轴组织的镜像复制。本提案的总体目标是鉴定和表征在背面细胞命运规范或分生组织潜能抑制和/或激活中发挥作用的基因和植物激素

Bowman9986054While 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 twoconditions: 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 andphytohormones that play a role in either specification of abaxial cell fate or suppression and/or activation of meristematic potential