Metabolites 2014, 4(3), 532-546; doi:10.3390/metabo4030532

Insect-Induced Daidzein, Formononetin and Their Conjugates in Soybean Leaves

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Received: 29 April 2014; in revised form: 23 June 2014 / Accepted: 24 June 2014 / Published: 4 July 2014
(This article belongs to the Special Issue Metabolomics and Biotechnology)
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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.
Keywords: plant-insect interaction; plant induced resistance; insect-produced elicitors; isoflavones; insect herbivory; secondary metabolites; liquid chromatography; mass spectrometry
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MDPI and ACS Style

Murakami, S.; Nakata, R.; Aboshi, T.; Yoshinaga, N.; Teraishi, M.; Okumoto, Y.; Ishihara, A.; Morisaka, H.; Huffaker, A.; Schmelz, E.A.; Mori, N. Insect-Induced Daidzein, Formononetin and Their Conjugates in Soybean Leaves. Metabolites 2014, 4, 532-546.

AMA Style

Murakami S, Nakata R, Aboshi T, Yoshinaga N, Teraishi M, Okumoto Y, Ishihara A, Morisaka H, Huffaker A, Schmelz EA, Mori N. Insect-Induced Daidzein, Formononetin and Their Conjugates in Soybean Leaves. Metabolites. 2014; 4(3):532-546.

Chicago/Turabian Style

Murakami, Shinichiro; Nakata, Ryu; Aboshi, Takako; Yoshinaga, Naoko; Teraishi, Masayoshi; Okumoto, Yutaka; Ishihara, Atsushi; Morisaka, Hironobu; Huffaker, Alisa; Schmelz, Eric A.; Mori, Naoki. 2014. "Insect-Induced Daidzein, Formononetin and Their Conjugates in Soybean Leaves." Metabolites 4, no. 3: 532-546.

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