The regulation of flowering in Arabidopsis thaliana: meristems, morphogenesis, and mutants

In the last decade, the study of mutants defective in floral development has contributed significantly to our understanding of floral evocation and morphogenesis. Genes in Arabidopsis thaliana and Antirrhinum majus that play key roles in (i) the transition from the vegetative to reproductive phase, (ii) the activation of floral development in specific shoots, and (iii) the unique arrangement of floral organs have been identified genetically and in many cases cloned. Many of the genes appear to encode transcription factors that act to select specific developmental programs of division and differentiation for groups of primordial cells. Other genes may be involved in detecting environmental conditions and transducing the signal to the developing meristems. Key questions remaining include how the regulatory proteins are produced in specific temporal and spatial patterns, interact with each other and initiate specific morphological programs. Although current research on floral morphogenesis has been limited to only a few species there is growing evidence that the basic processes are common to all flowering plants.Thus the information and tools currently being generated should be useful for studying a wide variety of flowering species. It seems reasonable to predict that within the next decade, we should have a fairly complete understanding of the basic mechanisms underlying floral morphogenesis and its evolution among the angiosperms. Key words: Arabidopsis thaliana, floral morphogenesis, molecular genetics.