Abstract

Without a dedicated germ line, how do plant cells differentiate for meiosis? We are studying the steps in maize anther ontogeny from anther primordium inception until the onset of meiosis. The first step is production 4 lobes on each anther establishing the locules and overall anther morphology. Within the locules we have charted the successive specification of cell types: in order of appearance epidermal cells from the L1 and in the L2 the archesporial, then the endothecial and secondary parietal cell types, and finally the middle layer and tapetal cell types. Using confocal reconstruction and analysis of maize mutants, we have developed a new theory for the specification of the archesporial (pre-meiotic cells) and somatic cell types to replace the classic lineage model. These microscopic analyses are complemented by the cloning of key genes controlling steps in anther cell differentiation and by microarray and proteomic analyses of whole anthers and individual cell types. We have also discovered physiological conditions that can overcome mutations in cell fate specification and propose that a combination of developmental and physiological cues operate in situ during key steps in anther cell fate determination.