title: Insect-induced daidzein, formononetin and their conjugates in soybean leaves.
abstract: In response to attack by bacterial pathogens, soybean (Gylcine max) leaves accumulate isoflavone aglucones, isoflavone glucosides, and glyceollins. In contrast to pathogens, the dynamics of related insect-inducible metabolites in soybean leaves remain poorly understood. In this study, we analyzed the biochemical responses of soybean leaves to Spodoptera litura (Lepidoptera: Noctuidae) herbivory and also S. litura gut contents, which contain oral secretion elicitors. Following S. litura herbivory, soybean leaves displayed an induced accumulation of the flavone and isoflavone aglycones 4',7-dihyroxyflavone, daidzein, and formononetin, and also the isoflavone glucoside daidzin. Interestingly, foliar application of S. litura oral secretions also elicited the accumulation of isoflavone aglycones (daidzein and formononetin), isoflavone 7-O-glucosides (daidzin, ononin), and isoflavone 7-O-(6'-O-malonyl-β-glucosides) (malonyldaidzin, malonylononin). Consistent with the up-regulation of the isoflavonoid biosynthetic pathway, folair phenylalanine levels also increased following oral secretion treatment. To establish that these metabolitic changes were the result of de novo biosynthesis, we demonstrated that labeled (13C9) phenylalanine was incorporated into the isoflavone aglucones. These results are consistent with the presence of soybean defense elicitors in S. litura oral secretions. We demonstrate that isoflavone aglycones and isoflavone conjugates are induced in soybean leaves, not only by pathogens as previously demonstrated, but also by foliar insect herbivory.
authors.affiliation: Graduate School of Agriculture, Kyoto University, Kitashirakawa, Sakyo, Kyoto 606-8502, Japan. murakami.shinichiro.85e@st.kyoto-u.ac.jp.
authors.forename: Shinichiro
authors.initials: S
authors.lastname: Murakami
authors.affiliation: Graduate School of Agriculture, Kyoto University, Kitashirakawa, Sakyo, Kyoto 606-8502, Japan. nakata.ryu.ski@gmail.com.
authors.forename: Ryu
authors.initials: R
authors.lastname: Nakata
authors.affiliation: Graduate School of Agriculture, Kyoto University, Kitashirakawa, Sakyo, Kyoto 606-8502, Japan. frecher@kais.kyoto-u.ac.jp.
authors.forename: Takako
authors.initials: T
authors.lastname: Aboshi
authors.affiliation: Graduate School of Agriculture, Kyoto University, Kitashirakawa, Sakyo, Kyoto 606-8502, Japan. yoshinaga.naoko.5v@kyoto-u.ac.jp.
authors.forename: Naoko
authors.initials: N
authors.lastname: Yoshinaga
authors.affiliation: Graduate School of Agriculture, Kyoto University, Kitashirakawa, Sakyo, Kyoto 606-8502, Japan. temple@kais.kyoto-u.ac.jp.
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Teraishi
authors.affiliation: Graduate School of Agriculture, Kyoto University, Kitashirakawa, Sakyo, Kyoto 606-8502, Japan. okumoto3@kais.kyoto-u.ac.jp.
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Okumoto
authors.affiliation: Department of Agriculture, Tottori University, Koyama-machi 4-101, Tottori 680-8550, Japan. aishihara@muses.tottori-u.ac.jp.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Ishihara
authors.affiliation: Graduate School of Agriculture, Kyoto University, Kitashirakawa, Sakyo, Kyoto 606-8502, Japan. morisaka@kais.kyoto-u.ac.jp.
authors.forename: Hironobu
authors.initials: H
authors.lastname: Morisaka
authors.affiliation: Center for Medical, Agricultural, and Veterinary Entomology, Agricultural Research Service, USDA, 1600 S.W. 23RD Drive, Gainesville, FL 32606, USA. alisa.huffaker@ars.usda.gov.
authors.forename: Alisa
authors.initials: A
authors.lastname: Huffaker
authors.affiliation: Center for Medical, Agricultural, and Veterinary Entomology, Agricultural Research Service, USDA, 1600 S.W. 23RD Drive, Gainesville, FL 32606, USA. Eric.Schmelz@ars.usda.gov.
authors.forename: Eric A
authors.initials: EA
authors.lastname: Schmelz
authors.affiliation: Graduate School of Agriculture, Kyoto University, Kitashirakawa, Sakyo, Kyoto 606-8502, Japan. mori.naoki.8a@kyoto-u.ac.jp.
authors.forename: Naoki
authors.initials: N
authors.lastname: Mori