Specification of floral meristem identity by repressing flowering time genes

Abstract

In Arabidopsis, the floral meristem identity genes LEAFY (LFY) and APETALA1 (AP1) are activated to play pivotal roles in specifying floral meristems during floral transition. When the activity of either gene is lost or up-regulated, meristems that would normally develop into flowers are converted into shoot-like structures or vice versa. In this thesis we show that floral meristems initiate like shoot meristems and require AP1 to repress directly flowering-time integrators to specify partly their floral identities. Without AP1 activity, these flowering-time integrators can interact ectopically to transform the meristems of perianth floral organs into shoot meristems. We demonstrate the repression of these flowering time genes by induced AP1 activity as immediate targets of AP1 protein. AP1 is activated during the floral transition, it acts partly as a master repressor in floral meristems, providing a feedback regulation of flowering time genes to prevent the meristem reversion during flower development.