The Role of Lipoxygenases in Mediating Defense Response to Perception of Herbivore-Induced Plant Volatiles in Maize
Abstract
Volatile organic compounds (VOCs) are one means for inter- and intra-plant signal communication. One such group of volatiles produced in response to insect herbivory are herbivore-induced plant volatiles (HIPVs), which allow uninfested plants in close proximity to infested plants to pre-emptively raise their defenses to impending insect attack. Plant response to HIPVs involves the synthesis of various lipoxygenase (LOX)-derived oxylipins, including a well-known phytohormone that participates in insect defense, jasmonic acid (JA). Importantly, LOXs can collectively synthesize many diverse metabolites, however, whether any of these other oxylipins are involved in insect defense or HIPV response remain largely unknown. Green leaf volatiles (GLVs) are a major group of oxylipin HIPVs and are known to induce the expression of specific LOXs. Several maize knockout mutant lines disrupted in specific LOX genes were chosen because expression of those genes is GLV-inducible. Therefore, these mutants are hypothesized to lack appropriate defense metabolite responses to HIPVs. By selectively testing metabolite responses of lox mutants to HIPVs, we aim to identify LOX isoforms that are involved in HIPV response and the specific signaling metabolites they generate. This project aims to identify the role of LOX5 and LOX10 in the response of Zea mays to HIPVs. We performed experiments in which fall armyworm (FAW) are allowed to feed on wild-type maize seedlings resulting in the production of HIPVs. Such infested plants are termed “emitters”. The lox mutants exposed to emitter volatiles are termed “receivers”. We then collected leaf tissues from the receiver plants and quantified a large number of oxylipins and several major defense phytohormones via liquid chromatography tandem mass spectrometry (LC-MS/MS). This analysis revealed significant perturbations in metabolite accumulation in several HIPV-induced oxylipins in lox5 mutants. lox10 mutants were deficient in a multitude of 13-oxylipins, confirming that it plays a major role in the HIPV response. Collectively, these results have revealed that both of these LOX isoforms play a significant role in HIPV-mediated defense priming against FAW.
Subject
jasmonic acidgreen leaf volatile
herbivore-induced plant volatile
lipoxygenase
fall armyworm
interplant signaling
Citation
Toomey, Katie E (2022). The Role of Lipoxygenases in Mediating Defense Response to Perception of Herbivore-Induced Plant Volatiles in Maize. Undergraduate Research Scholars Program. Available electronically from https : / /hdl .handle .net /1969 .1 /194409.