Isopentylamine is a novel defence compound induced by insect feeding in rice

Abstract

Plants produce a broad variety of defensive metabolites to protect themselves against herbivorous insects. Although polyamines have been implicated in various responses to abiotic and biotic stress, there have been no studies focused on amines in response to insect herbivory. By screening for bioactive amines, we identified isopentylamine as a novel type of herbivory-induced compound in rice leaves, which was derived from the amino acid leucine in stable isotope labelling experiments. Accumulation of isopentylamine increased during herbivory by the brown planthopper (Nilaparvata lugens, BPH) and the rice-feeding armyworm (Mythimna loreyi), as well as in response to treatment with the plant hormone, jasmonic acid. Likewise, isopentylamine accumulation was compromised in rice jasmonate biosynthesis mutants, hebiba and Osjar1. In bio-assays, BPH insects feeding on rice seedlings submerged in 50 mg/L isopentylamine solution had a higher mortality compared with BPH feeding on seedlings submerged in water. Notably, the rice leaves submerged in 50 mg/L solution showed the endogenous concentrations of isopentylamine similar to that induced by BPHs. These results suggest that isopentylamine functions as a new type of plant defence metabolite that is rapidly induced by herbivore attack and deters insect herbivores in rice.

Integrated view of plant metabolic defense with particular focus on chewing herbivores

“…So far, Bxs type of metabolites have not been reported in another important monocot crop rice ( Oryza sativa ) (Kokubo et al, 2017). Instead, herbivore attack elicits a distinct set of N ‐containing compounds in rice, such as the recently identified isopentylamine (iPA; Aboshi et al, 2021). While iPA production is elicited by herbivory, it is also produced in rice treated with exogenous JA (Aboshi et al, 2021).…”

“…Instead, herbivore attack elicits a distinct set of N ‐containing compounds in rice, such as the recently identified isopentylamine (iPA; Aboshi et al, 2021). While iPA production is elicited by herbivory, it is also produced in rice treated with exogenous JA (Aboshi et al, 2021). Although direct toxicity to caterpillars could not be demonstrated in this report, lower survival of specialist sucking pests N. lugens was reported in adults that fed on rice cuttings dipped in water supplemented with iPA.…”

Rice functional genomics: decades’ efforts and roads ahead

“…Isopentylamine functions as a new type of plant defense metabolite against BPH. Its rapid accumulation in rice under herbivore attack is completely dependent on JA signaling (Aboshi et al, 2021).…”

Comprehensive analysis of silicon impact on defense and metabolic responses in rice exposed to herbivory stress

“…Such enzymes are often associated with the biosynthetic pathways for various types of defensive secondary metabolites, including various types of phenolics and momilactones ( Fawe et al., 1998 ; Ahanger et al., 2020 ). Previously, we characterized several novel herbivore-induced metabolites in rice, which is a typical hyperaccumulator of Si ( Alamgir et al., 2016 ; Aboshi et al., 2021 ); however, whether Si could be mediating the content of these metabolites in rice defense remains unknown.…”