GENETIC INTERACTIONS THAT REGULATE INFLORESCENCE DEVELOPMENT IN ARABIDOPSIS

In Arabidopsis, floral meristems arise in continuous succession direct ly on the flanks of the inflorescence meristem. Thus, the pathways tha t regulate inflorescence and floral meristem identity must operate bot h simultaneously and in close spatial proximity. The TERMINAL FLOWER 1 (TFL1) gene of Arabidopsis is required for normal inflorescence meris tem function, and the LEAFY (LFY), APETALA 1 (AP1), and APETALA 2 (AP2 ) genes are required for normal floral meristem function. We present e vidence that inflorescence meristem identity is promoted by TFL1 and t hat floral meristem identity is promoted by parallel developmental pat hways, one defined by LFY and the other defined by AP1/AP2. Our analys is suggests that the acquisition of meristem identity during infloresc ence development is mediated by antagonistic interactions between TFL1 and LFY and between TFL1 and AP1/AP2. Based on this study, we propose a simple model for the genetic regulation of inflorescence developmen t in Arabidopsis. This model is discussed in relation to the proposed interactions between the inflorescence and the floral meristem identit y genes and in regard to other genes that are likely to be part of the genetic hierarchy regulating the establishment and maintenance of inf lorescence and floral meristems.