Crop yield losses caused by plant diseases are in the value of billions of dollars worldwide each year, which has made it an alarming threat to the food security in feeding a burgeoning global population. Understanding and eventually manipulating for crop improvement the key molecular mechanisms which plants use to defend against various pathogens is thus of considerable agricultural, economic, and social importance. Among the mechanisms pivotal for host defense is ubiquitination, a major post-translational protein modification process that occurs in plant, animal, and human cells. A particular type of unconventional modification of proteins by ubiquitin (lysine-63-linked ubiquitination, is well documented to be crucial in modulating human and animal innate and adaptive immunity. However, the roles of this type of ubiquitination in plant immunity and other plant physiological processes have been significantly understudied, even though this type of ubiquitnation is the second most abundant type of ubiquitination in plants. This project investigates the mechanistic basis of regulating plant innate immunity by this type of unconventional ubiquitination and includes education development for high school science teachers and minority undergraduate students and outreach to the Nebraska farmers and stakeholders.
Initial work of this project has identified and preliminarily implicated two tomato RING type ubiquitin ligases, Fti1 and Fti1B and their closest homolog in Arabidopsis, AtFti1 and AtFti1B, respectively in FLS2-mediated plant pattern-triggered immunity (PTI). Fti1 and Fti1B and their Arabidopsis closest homolog were found to interact and work with UBC13 type ubiquitin-conjugating enzyme to catalyze K63-linked ubiquitination and Fti1B and AtFti1B were shown to be functionally conserved in FLS2-mediated PTI. Additionally, an isoform of AtFti1B was found to change subcellular localization to a yet undetermined organelle after PTI was induced by flg22 in the cell. In this project the investigators will elucidate the molecular mechanism underlying the regulation of plant PTI by AtFti1B/Fti1B-mediated K63-linked ubiquitination, with aims to (1) determine the role of AtFti1B isoforms in PTI and the molecular outcome of AtFti1B-BAK1/FLS2 interaction; (2) elucidate the biological significance of AtFti1B-BAK1/FLS2 interaction, the E3 ligase activity of AtFti1B, and the AtFti1B subcellular localization in plant immunity; and (3) identify novel components that are involved in the regulation of plant immunity by AtFti1B-mediated Lys63 ubiquitination. Fulfillment of this project will help integrally address two important, yet elusive questions in plant immunity: what are the roles and mechanisms of Lys63-linked ubiquitination and cell organelles in plant immune signaling. Considering the limited knowledge of Lys63-linked ubiquitination in plant biology in general, findings from this project will also assist our efforts to understand Lys63-linked ubiquitination in other plant physiological processes. Integral to this project will be extensive education and outreach activities to train high school science teachers and minority undergraduate students that are underrepresented in science through a High School and Undergraduate Science Connect Promoting Keen Interests in Research (HUSKER) program and to educate Nebraska farmers and stakeholders about the importance of basic research in crop improvement.
