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PhD Exit Seminar – Eliana Vonapartis (Gazzarrini Lab)

June 30, 2021 @ 1:10 pm - 2:00 pm

The Transcriptional Regulation and Role of XERICO in Arabidopsis thaliana Development and Stress Responses



Every year, periods of agricultural drought devastate crop yields globally, limiting food production and leading to significant economic losses. The phytohormone abscisic acid (ABA) accumulates during drought and is crucial for the plant to mount an effective stress response. Arabidopsis thaliana XERICO (XER) is a stress-inducible E3 ubiquitin ligase that plays a role in regulating ABA levels, stomatal closure, and drought tolerance. While the function XER in ABA homeostasis and drought tolerance has been substantiated in various monocot and dicot species, other roles for XER in controlling plant stress responses remain unknown. In addition, knowledge of the mechanisms governing XER transcriptional regulation under stress conditions is limited. Thus, this work aimed to further characterize the function of XER in Arabidopsis stress responses and to shed light on the regulation of its spatiotemporal expression pattern by stress stimuli. The data in this thesis demonstrate that XER expression is repressed by stress-responsive CBF4/DREB1D, which was identified by yeast one-hybrid screening and established as a negative regulator of ABA responses and drought tolerance through CRISPR/Cas9 mutant analysis. Furthermore, by characterizing loss-of-function xer mutants and transgenic lines overexpressing a RING-mutated XER variant, XER was found to inhibit stomatal development and gibberellin (GA) signaling. Lastly, 88 ABA-regulated putative XER interactors were identified by high-throughput yeast two-hybrid screening, unveiling potential mechanisms and pathways through which XER may modulate ABA and stress responses. Overall, the results presented in this thesis reveal that XER contributes to stress responses by enhancing ABA and repressing GA signaling, as well as by restricting stomatal development, and that tight transcriptional control of XER expression by CBF4 is important for the plant to balance plant growth and survival under adverse environmental conditions such as drought.


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Meeting ID: 848 2745 5870

Host: Sonia Gazzarrini (sonia.gazzarrini@utoronto.ca)



June 30, 2021
1:10 pm - 2:00 pm
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