Oxidative post-translational modifications in plant-insect interactions

点击翻译按钮获取中文摘要

Due to the increasing demands on agricultural lands to supply food as well as biofuels crops, the need to increase plant productivity has never been higher. The reduction of crop losses due to insect herbivory is an important way to maintain or increase plant productivity, particularly since agricultural losses to caterpillar pests are predicted to increase in the future as global warming progresses. Plants have multiple mechanisms to protect themselves against caterpillar herbivory. However, insect herbivores also have strategies to counteract or detoxify these plant defenses. For example, some noctuid caterpillars contain effector(s) in their labial saliva that can delay or suppress plant induced defenses. Noctuid caterpillars are globally-widespread herbivores of many plants, including agricultural, biofuel and horticultural species. When they feed on the plant, they secrete labial saliva that results in the lowering of plant defenses. Using cutting-edge molecular and biochemical techniques, we are studying the mechanisms underlying this with the goal of developing sustainable agricultural pest management strategies. When plants are wounded by caterpillars, rapid biochemical changes generate a jasmonate-mediated defensive cascade. These changes are too rapid to involve gene expression. Therefore, other cellular regulatory mechanisms, such as protein post-translational modifications (PTMs), must be involved. Generalist noctuid caterpillar labial saliva contains enzymes, such as glucose oxidase that generates hydrogen peroxide; this reactive oxygen species may mediate the PTMs of cellular proteins, specifically amino acid modifications such as cysteine-oxidation or cysteine-glutathionylation. Such oxidative stress-related PTMs have been identified in other systems; however, little is known about the role of these reactive oxygen species-related PTMs in plant-insect interactions. Therefore, we propose to elucidate the mechanisms used by generalist noctuid larva to undermine induce plant defenses by identifying and characterizing reactive oxygen species-mediated protein PTMs. In addition, we previously identified caterpillar labial saliva-specific dephosphorylation of lipoxygenase 2, a key enzyme in jasmonate biosynthesis. Regulation of lipoxygenase 2 activity by PTM provides an excellent means of caterpillar labial saliva-mediated suppression of induced plant defenses. Therefore, as well as reactive oxygen species-associated PTMs, we will characterize lipoxygenase 2 dephosphorylation in plant-insect interactions. By elucidating protein PTM networks in response to caterpillar herbivory, we hope to understand how labial saliva subverts plant defenses and identify endogenous targets for breeding programs to enhance plant resistance to chewing insect herbivory. Through this research, 4 graduate students (2 PhD and 2 MSc), 5 undergraduates and a part-time research technician will gain expertise in plant molecular biology and physiology, areas of high demand in vital Canadian industries, such as agriculture and biotechnology.