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PhD Transfer Exam – Paula Beronilla (Goring lab)
January 29 @ 12:30 pm - 1:00 pm
PhD Transfer Exam
Wednesday, January 29, 2020 at 12:30 pm – Earth Sciences Centre, Room 3043
Paula Beronilla (Goring lab)
“Investigating Candidate Players in the Compatible and Self-incompatible Pollen Response Pathways in the Brassicaceae”
Following pollination, the dry stigmas in the Brassicaceae rapidly regulate pollen-stigma interactions, thereby leading to the acceptance of compatible pollen or the rejection of self-incompatible (SI) pollen. The compatible pollen response pathway enables pollen hydration, germination, and pollen tube growth ultimately leading to the fertilization of ovules. Contrary to that, the self-incompatible pollen response pathway inhibits the secretory events in the stigma required for these early stages. The objective of this proposed research is to investigate putative players in the compatible and self-incompatible pollen response pathways. The first player to be investigated in the compatible pollen response pathway is MSL7. Emerging studies on MSL proteins have revealed the requirement of the pollen specific MSL8 for pollen viability by regulating osmotic stress in the plasma membrane of the pollen during fertilization. Interestingly, MSL8 is tandemly linked to MSL7 which displays stigma-specific expression. Thus, we aim to determine if MSL7 is required in the stigma during compatible pollen responses to potentially regulate pollen hydration. Previous studies have shown that the compatibility and the self-incompatibility pathways intersect at the secretory step mediated by the exocyst complex. In the SI pathway, ARC1 has been previously shown to inhibit the function Exo70A1, a member of the exocyst complex, in the delivery of resources and nutrients required for pollen hydration and germination. Knockdown of ARC1 in two different Brassicaceae species has caused a partial breakdown of SI responses. However, more recent studies have shown that transgenic A. thaliana ecotype C24 exhibits a robust SI phenotype despite lacking ARC1, when transformed with other SI upstream players. The closest paralog of ARC1 is PUB17 and we hypothesize that PUB17 is contributing to SI responses by playing a similar biological function to ARC1. Thus, I will investigate PUB17 through its knockout in the transgenic SI C24. Finally, I am also investigating how the SI response would be affected with the complete knockout of ARC1 in other Brassicaceae species, specifically in Capsella. Further elucidation and characterization of the role of these candidate players would provide better understanding of the signaling events underlying both pollen response pathways for regulation of plant reproduction.