XVI International Botanical Congess

The shoot apical meristem (SAM) which give rise to the aerial parts of the plant is formed by a small number of dividing cells. According to a widely accepted model, different zones based on proliferation rate variations have been defined with in the SAM: a peripheral zone with a relative high mitotic activity surrounds a central zone with a lower mitotic activity. In the last few years, mutants which potentially affect the cell cycle control in the SAM have been described in several species including Arabidopsis thaliana. Unfortunately, no precise description of the mitotic activity in wild-type Arabidopsis nor in any mutant has been done. Using confocal laser microscopy and image analysis, the spatial regulation of the mitotic activity within vegetative and inflorescence wild-type meristem of Arabidopsis has been analyzed. This frame of reference was then used to analyze the mitotic activity within several Arabidopsis mutants with abnormal meristem development including clavata 3, mgoun2 and pinformed1. We show that , in these mutants, the spatial regulation of the mitotic activity is affected in different ways.