PhD Transfer Exam – Hyun Kyung Lee (Goring lab)

PhD Transfer Exam

Wednesday May 4^th, 1:10 pm – Earth Sciences Centre, Rm. ESC 3087

Hyun Kyung Lee (Goring lab)

“Investigating the roles of receptor-like cytoplasmic kinases in Brassicaceae pollen-stigma signalling pathways“

Abstract

Plants have evolved a large number of receptor-like cytoplasmic kinases (RLCKs) that interact with membrane bound receptors to modulate signalling cascades. The focus of my research is on putative RLCKs regulating the initial stages of pollen-stigma interactions in plant reproduction. Once pollen is captured, the stigmatic papillae initiates signalling cascades to deliver water to the pollen grain for hydration and loosen the papillar cell wall for pollen tube entry.  However, key signalling components which govern these molecular changes are currently unknown. Simultaneously, in self-incompatible species, the self-incompatibility (SI) pathway can also be activated to circumvent the compatible pollen responses and reject self-pollen. The objective of my PhD thesis is to investigate two putative Arabidopsis thaliana RLCKs pairs, PASK1/2 and APK1a/b, in the compatible and SI signaling pathways, respectively.  PASK1/2 are pseudokinases required in the stigma for accepting compatible pollen and may function as scaffolding proteins. In order to elucidate their putative interactors, yeast two-hybrid screening of a flower bud cDNA library was conducted and several potential interactors were identified. To further investigate the specificity of theses interactions, in planta interactions and knockdown and/or knockout lines will be characterized for reduced compatible pollen acceptance. APK1a/b are orthologues of the Brassica SI protein, MLPK, and their role in the A. thaliana SI response is being investigated.  Characterization of the SI trait in apk1a/apk1b double knockout lines in the transgenic SI A. thaliana Col-0 lines has given mixed results which may be due to silencing of SI transgenes in the Col-0 ecotype.  New A. halleri SI constructs have been cloned and will be tested in the A. thaliana C24 and Sha ecotypes which are known to produce stronger and stable SI phenotypes.  SI lines will be generated, and the APK1a/b genes will be silenced using the CRISPR/Cas9 system to induce gene-specific mutations. Overall, this project will provide insight into the roles of two RLCKs pairs in stigmatic papillar signaling pathways regulating the acceptance or rejection of pollen in A. thaliana.