Cellular regulation of pollen compatibility and fertility in the Brassicaceae

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In the Brassicaceae (mustard family), sexual plant reproduction is initiated when pollen grains (male) are deposited on top of the pistil (female). Compatible pollen grains are recognized by the pistil and provided resources so that the pollen grains can germinate and produce pollen tubes to deliver sperm cells for fertilization. These pollen-pistil interactions are tightly-regulated and critical as fertilization initiates seed production. The Goring research group examines the first stage of these interactions: when the pollen comes in contact with stigmatic papillar cells at the top of pistil. These papillae can differentiate between different pollen to accept, reject or ignore the pollen grains. Compatible pollen is accepted as it is recognized as being closely-related. In contrast, self'-pollen is rejected in many species as this self-recognition system is used to prevent inbreeding (self-incompatibility). Finally, pollen that is ignored is simply too distantly-related to be recognized. Thus, these initial interactions carefully regulate and conserve the sharing of resources from the female pistil to the male pollen for successful fertilization.***For this grant proposal, the Goring research group will investigate the cell-cell communication events that regulate the initial pollen-stigmatic papillae interactions and examine how these processes are conserved in different Brassicaceae species. Specifically, three objectives are proposed for this research:***(1) Identify and characterize the signaling proteins in the stigmatic papillae (pistil) that are responsible for recognizing and responding to compatible pollen (e.g. receptors). The mechanism by which stigmatic papillae recognize compatible pollen is currently unknown.***(2) Investigate the mechanism of regulated secretion in the basal compatible pollen response pathway. This is the cellular system in the stigmatic papillae that is hypothesized to be responsible for allocating resources to the compatible pollen grains.***(3) Define the role and mechanism of autophagy in self-incompatible pollen rejection. This is a cellular response in the stigmatic papillae that is hypothesized to play an important role in rejecting self'-pollen to prevent inbreeding. ***Through these three objectives, the proposed research is expected to lead to significant new discoveries on the mechanisms regulating early post-pollination processes in the Brassicaceae. Ultimately, successful compatible pollen acceptance has a positive impact on fertilization and seed production, and self-incompatible pollen rejection prevents inbreeding to produce healthier offspring. Hence, this research has important implications for developing new strategies to improve seed productivity in Brassicaceae oilseed crops such as canola.