Lookup NU author(s): Dr Nawaporn Onkokesung
This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).
Anthocyanins and flavonols are secondary metabolites that can function in plant defence against herbivores. In Arabidopsis thaliana, anthocyanin and flavonol biosynthesis are regulated by MYB transcription factors. Overexpression of MYB75 (oxMYB75) in Arabidopsis results in increasing anthocyanin and flavonol levels which enhances plant resistance to generalist caterpillars. However, how these metabolites affect specialist herbivores has remained unknown. Performance of a specialist aphid (Brevicoryne brassicae) was unaffected after feeding on oxMYB75 plants, whereas a specialist caterpillar (Pieris brassicae) gained significantly higher body mass when feeding on this plant. An increase in anthocyanin and total flavonol glycoside levels correlated negatively with the body mass of caterpillars fed on oxMYB75 plants. However, a significant reduction of kaempferol-3,7-dirhamnoside (KRR) corresponded to an increased susceptibility of oxMYB75 plants to caterpillar feeding. Pieris brassicae caterpillars also grew less on an artificial diet containing KRR or on oxMYB75 plants that were exogenously treated with KRR, supporting KRR’s function in direct defence against this specialist caterpillar. The results show that enhancing the activity of the anthocyanin pathway in oxMYB75 plants results in re-channelling of quercetin/kaempferol metabolites which has a negative effect on the accumulation of KRR, a novel defensive metabolite against a specialist caterpillar.
Author(s): Onkokesung N, Reichelt M, van Doorn A, Schuurink RC, van Loon JJA, Dicke M
Publication type: Article
Publication status: Published
Journal: Journal of Experimental Botany
Print publication date: 01/05/2014
Online publication date: 11/03/2014
Acceptance date: 12/02/2014
ISSN (print): 0022-0957
ISSN (electronic): 1460-2431
Publisher: Oxford University Press
Notes: Specialist herbivores are well-adapted to host plant defence metabolites. In fact, specialist herbivores i.e. Pieris brassicae caterpillars use glucosinolates, a major defence metabolite in Brassicaceae family including Arabidopsis, as a feeding cue. Hence host plants do not rely on a specific class of defence metabolite to defence themselves against specialist herbivores. A mixture or ‘cocktail’ of defence metabolites has been proposed to play an important role to protect host plants against their specialist herbivores. In this study, we demonstrate that in combination with glucosinolates, kaempferol dirhamnoside (KRR) is an active defence metabolite against P. brassicae caterpillars. Moreover, we also demonstrated that MYB75, a master transcript regulator of anthocyanin biosynthetic pathway, also exerted some control on flavonol glycosides biosynthetic pathway. This study is another example of using master transcript regulator in metabolite engineering to improve plant resistances against a specialist caterpillar attack.
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