A genomic approach to elucidating grass flower development.pdf

A genomic approach to elucidating grass flower development Marcelo C. Dornelas1* and Adriana P.M. Rodriguez2 Abstract In sugarcane (Saccharum sp) as with other species of grass, at a certain moment of its life cycle the vegetative meristem is converted into an inflorescence meristem which has at least two distinct inflorescence branching steps before the spikelet meristem terminates in the production of a flower (floret). In model dicotyledonous species such successive conversions of meristem identities and the concentric arrangement of floral organs in specific whorls have both been shown to be genetically controlled. Using data from the Sugarcane Expressed Sequence Tag (EST) Project (SUCEST) database, we have identified all sugarcane proteins and genes putatively involved in reproductive meristem and flower development. Sequence comparisons of known flower-related genes have uncovered conserved evolutionary pathways of flower development and flower pattern formation between dicotyledons and monocotyledons, such as some grass species. We have paid special attention to the analysis of the MADS-box multigene family of transcription factors that together with the APETALA2 (AP2) family are the key elements of the transcriptional networks controlling plant reproductive development. Considerations on the evolutionary developmental genetics of grass flowers and their relation to the ABC homeotic gene activity model of flower development are also presented. INTRODUCTION Grasses, like all higher plants, develop by the elabora- tion of populations of undifferentiated stem cells (meris- tems) which give rise to all the organs of the plant. The shoot apical meristem (SAM) is the ultimate source for all aerial structures of the plant, including flowers. The iden- tity of a meristem is defined by the types of structures it pro- duces, and in sugarcane the shoot meristem undergoes several distinct transitions in identity during the life of the plant. A major transition occurs whe