Format: ORAL

Barbara A. Ambrose

New York Botanical Garden. Bronx, NY. USA.

A salient feature of the diploid sporophyte is the development of the sporangium, the fundamental reproductive structure of all land plants. Whether the structure is a cone, strobilus, or flower all are clusters of sporangia. The sporangium is where meiosis occurs to produce spores, marking the transition between the diploid and haploid phases of the plant life cycle.In all land plants, sporangium development begins when a somatic cell is specified to be reproductive and then undergo a series of stereotypical divisions, and cell fate decisions that gives rise to the sporangium. The developmental anatomy of sporangia has been studied across land plants. From an evolutionary point of view, sporangia are key to land plant success. The evolution of distinct sporangia (heterospory) and retention of the gametophyte evolved three times independently and was a necessary innovation for the subsequent evolution of the seed. The well-known nucellus and pollen sac are the sporangia of flowering plants and the molecular genetics of their development has been well studied, particularly inArabidopsis thaliana.Despite its fundamental importance, we lack a comprehensive understanding of the evolutionary developmental genetics of sporangia development across land plants.To fill this gap, we are investigating the development and molecular genetics of sporangia in lycophytes and ferns with a focus on the fern model system,Ceratopteris richardii.We are studying the development of sporangia in lycophytes and ferns using histochemical staining and microscopy.We are investigating the molecular genetics ofC. richardiisporangia development using transcriptomics and a candidate gene approach. Despite differences in sporangia cell patterning betweenA. thalianaandC. richardii, we found homologous genes pattern sporangia in both species. This suggests that there is a common genetic module that patterns all sporangia and provides a framework for understanding theirevolution and development.