Inducible De Novo Biosynthesis of Isoflavonoids in Soybean Leaves by Spodoptera litura Derived Elicitors: Tracer Techniques Aided by High Resolution LCMS

Abstract

Isoflavonoids are a characteristic family of natural products in legumes known to mediate a range of plant-biotic interactions. For example, in soybean (Glycine max: Fabaceae) multiple isoflavones are induced and accumulate in leaves following attack by Spodoptera litura (Lepidoptera: Noctuidae) larvae. To quantitatively examine patterns of activated de novo biosynthesis, soybean (Var. Enrei) leaves were treated with a combination of plant defense elicitors present in S. litura gut content extracts and L-α-[ 13 C 9 , 15 N]phenylalanine as a traceable isoflavonoid precursor. Combined treatments promoted significant increases in 13 Clabeled isoflavone aglycones (daidzein, formononetin, and genistein), 13 C-labeled isoflavone 7-O-glucosides (daidzin, ononin, and genistin), and 13 C-labeled isoflavone 7-O-(6″-O-malonyl-β-glucosides) (malonyldaidzin, malonylononin, and malonylgenistin). In contrast levels of 13 C-labeled flavones and flavonol (4′,7-dihydroxyflavone, kaempferol, and apigenin) were not significantly altered. Curiously, application of fatty acid-amino acid conjugate (FAC) elicitors present in S. litura gut contents, namely N-linolenoyl-L-glutamine and N-linoleoyl-L-glutamine, both promoted the induced accumulation of isoflavone 7-O-glucosides and isoflavone 7-O-(6″-O-malonyl-β-glucosides), but not isoflavone aglycones in the leaves. These results demonstrate that at least two separate reactions are involved in elicitor-induced soybean leaf responses to the S. litura gut contents: one is the de novo biosynthesis of isoflavone conjugates induced by FACs, and the other is the hydrolysis of the isoflavone conjugates to yield isoflavone aglycones. Gut content extracts alone displayed no hydrolytic activity. The quantitative analysis of isoflavone de novo biosynthesis, with respect to both aglycones and conjugates, affords a useful bioassay system for the discovery of additional plant defense elicitor(s) in S. litura gut contents that specifically promote hydrolysis of isoflavone conjugates.

Z‐Ligustilide Exerted Hormetic Effect on Growth and Detoxification Enzymes of Spodoptera litura Larvae

“…For example, the induced accumulation of isoflavone 7-O-glucosides and isoflavone 7-O-(6′′-O-malonyl- β -glucosides) was observed after soybean (Var. Enrei) leaves were treated with a combination of plant defense elicitors present in S. litura gut content extracts [ 33 ]. Two isoflavone aglycones (daidzein and formononetin) and their conjugates (glucosides and malonyl glucosides) were found to increase in soybean leaves [Glycine max (L.) Merr.…”

Isoflavone Malonyltransferases GmIMaT1 and GmIMaT3 Differently Modify Isoflavone Glucosides in Soybean (Glycine max) under Various Stresses

“…Soybean tissues infected with pathogens produce isoflavonoid phytoalexins (coumestrol and glyceollins) in site during defense responses to pathogen attacks (Zavala et al, 2015; Nakata et al, 2016; Yoneyama et al, 2016). The fluctuations of endogenous isoflavones in various forms, such as glucosides and malonates, are also detected under various conditions, although their coding physiological meanings barely are understood (Suzuki et al, 2007; Dhaubhadel et al, 2008; Farag et al, 2008; Zhao et al, 2011; Zhao, 2015).…”

“…Isoflavonoids play a vital role in plant defense response against different biotic and abiotic stresses, such as plant-pathogen by acting as precursors for phytoalexins biosynthesis (Graham and Graham, 1991; Dixon, 2001; Zhao et al, 2005;Akashi et al, 2009; Zhou et al, 2011; Ishiga et al, 2015; Yoneyama et al, 2016), plant-insects (Murakami et al, 2014; Zavala et al, 2015; Nakata et al, 2016), plant-symbionts by providing signals for Nod gene stimulation and nodule development (Subramanian et al, 2007; Zhang et al, 2009; Yasuda et al, 2016), and abiotic environmental stresses (Gutierrez-Gonzalez et al, 2010; Tripathi et al, 2016). They also contribute significantly to health beneficiary properties of legume seed foods for improving human health against heart disease, female breast cancer, and cardiovascular disease (Shin and Lee, 2013; Lee et al, 2016).…”

Identification and functional analysis of diet-responsive genes in Spodoptera litura (Fabricius)

“…), are rich in iso avones. [12,13]. Derivatives of 1, 4-benzoxazin-3-one (BX) are the most common secondary metabolites in the plants of Poaceae, including maize (Zea mays L.) [14,15].…”