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Lan, Jiameng

University of British Columbia

Plants face constant threats from pathogens and pests in their surroundings. To combat these invaders and survive, plants have evolved a complex immune system. Pathogen infection activates local defense responses that transmit signals throughout the plant, leading to systemic acquired resistance (SAR). N-hydroxypipecolic acid (NHP) plays a critical role as a signal molecule in SAR, and FLAVIN-DEPENDENT MONOOXYGENASE 1 (FMO1) is an essential enzyme in NHP biosynthesis. The expression levels of FMO1 and subsequent NHP levels are tightly regulated. In my Ph.D. study, I aimed to identify and characterize regulators of the FMO1-mediated NHP signaling pathway. To achieve my aims, a genetic screen was conducted in the pFMO1::LUC background with the induction of nlp20. Two types of mutants were identified from the screen, constitutive expression of FMO1 (cef) mutants and induced expression of FMO1 (ief) mutants. Whole genome sequencing analysis and knock-out lines generated by the CRISPR-Cas9 system confirmed the mutated genes in cef1, cef2, and ief1 were ASI1-IMMUNOPRECIPITATED PROTEIN 3 (AIPP3), CARBOXYL-TERMINAL DOMAIN PHOSPHATASE-LIKE 2 (CPL2), and PHD finger-containing protein 2 (PHD2), respectively. These three genes have been reported to function in the same complex that regulates flowering time, and we specifically investigated their defense-related functions. High FMO1 expression was associated with enhanced resistance against Hyaloperonospora arabidopsidis (H.a.) Noco2 and Pseudomonas syringae pathovar tomato (P.s.t.) DC3000, as well as increased levels of defense-related hormones such as SA and NHP, expanding the understanding of epigenetic regulation from flowering to defense. Additionally, six more mutants with stronger LUC signals were selected from the genetic screen. Through analysis of whole genome sequencing data and the generation of knock-out lines using the CRISPR-Cas9 system, we confirmed that HUA ENHANCER 2 (HEN2) was the mutated gene in the cef3 mutant. The potential mutated genes of cef4, cef5, cef6, ief2, and ief3 were also collected based on the whole genome sequencing data. In summary, my Ph.D. research expands the understanding of regulators involved in the FMO1-mediated NHP signaling pathway, shedding light on its intricate mechanisms.

Text

2024-10-31

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/86212

Botany

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/