Abstract
Cnaphalocrocis medinalis is a major insect pest of rice in Asia. A few defensive enzymes were reported to show higher activities in a resistant rice line (Qingliu) than in a susceptible rice line (TN1) upon leaffolder infestation. However, the overall molecular regulation of the rice defense response against leaffolder herbivory is unknown. Here, differential proteomic analysis by SWATH-MS was performed to identify differentially expressed proteins between the two rice varieties, Qingliu and TN1, at four time points of leaffolder herbivory, 0, 6, 24, and 72 h. Gene Ontology (GO) enrichment of the differentially expressed proteins indicated overrepresentation of (1) photosynthesis, (2) amino acid and derivative metabolic process, and (3) secondary metabolic process. Phenylalanine ammonia lyase and chalcone synthase, which catalyze flavonoid biosynthesis, and lipoxygenase, which catalyzes jasmonic acid biosynthesis, exhibited higher expression in Qingliu than in TN1 even before insect herbivory. Momentary activation of the light reaction and Calvin cycle was detected in Qingliu at 6 h and 24 h of insect herbivory, respectively. At 72 h of insect herbivory, amino acid biosynthesis and glutathione-mediated antioxidation were activated in Qingliu. A defense response involving jasmonic acid signaling, carbon remobilization, and the production of flavonoids and glutathione could underlie the resistance of Qingliu to leaffolder.
Highlights
Rice production in Asia is affected by a harmful insect pest, Cnaphalocrocis medinalis (Guenée) (Lepidoptera: Pyralidae), known as the rice leaffolder[1]
After removing the unknown proteins annotated by Gene Ontology (GO), 505 proteins were retained for further analysis (Supplementary Table S1)
These findings suggest that Qingliu is capable of triggering its jasmonic acid (JA)-mediated defense machinery against C. medinalis faster than Taichung Native 1 (TN1). This unique capability of Qingliu may explain the lowered relative growth rate (RGR) of insects observed in Qingliu compared with TN1 in our previous study[4]. This differential proteomic study of C. medinalis-resistant Qingliu and C. medinalis-susceptible TN1 at different time points of insect herbivory has provided us with a time course simulation of the mechanism by which important biological processes are differentially regulated between the two varieties at the protein level
Summary
Rice production in Asia is affected by a harmful insect pest, Cnaphalocrocis medinalis (Guenée) (Lepidoptera: Pyralidae), known as the rice leaffolder[1]. The affected leaf blades appear white, so heavily infested fields may have ‘scorched’-looking patches This insect herbivore can complete three life cycles during each rice cropping season in Taiwan[3,4]. The expression of genes encoding cinnamyl alcohol dehydrogenase (CAD), a lignin biosynthetic enzyme, was induced following herbivore-mediated damage in leaves[16]. Another two enzymes, polyphenol oxidase (PPO) and peroxidase (POD), catalyze the oxidation of phenols to form quinones[14]. We aimed to detect differentially expressed proteins between Qingliu and TN1 rice leaves upon exposure to herbivory by C. medinalis caterpillars at four different time points. This is the first proteomic profiling study targeted at elucidating the complex defense response of rice against C. medinalis herbivory
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