TY - JOUR

T1 - How insects overcome two-component plant chemical defence

T2 - plant β-glucosidases as the main target for herbivore adaptation

AU - Pentzold, Stefan

AU - Zagrobelny, Mika

AU - Rook, Frederik

AU - Bak, Søren

PY - 2014

Y1 - 2014

N2 - Insect herbivory is often restricted by glucosylated plant chemical defence compounds that are activated by plantβ-glucosidases to release toxic aglucones upon plant tissue damage. Such two-component plant defences are widespreadin the plant kingdom and examples of these classes of compounds are alkaloid, benzoxazinoid, cyanogenic and iridoidglucosides as well as glucosinolates and salicinoids. Conversely, many insects have evolved a diversity of counteradaptationsto overcome this type of constitutive chemical defence. Here we discuss that such counter-adaptations occurat different time points, before and during feeding as well as during digestion, and at several levels such as the insects’feeding behaviour, physiology and metabolism. Insect adaptations frequently circumvent or counteract the activity ofthe plant β-glucosidases, bioactivating enzymes that are a key element in the plant’s two-component chemical defence.These adaptations include host plant choice, non-disruptive feeding guilds and various physiological adaptations aswell as metabolic enzymatic strategies of the insect’s digestive system. Furthermore, insect adaptations often act incombination, may exist in both generalists and specialists, and can act on different classes of defence compounds. Wediscuss how generalist and specialist insects appear to differ in their ability to use these different types of adaptations:in generalists, adaptations are often inducible, whereas in specialists they are often constitutive. Future studies aresuggested to investigate in detail how insect adaptations act in combination to overcome plant chemical defences andto allow ecologically relevant conclusions.

AB - Insect herbivory is often restricted by glucosylated plant chemical defence compounds that are activated by plantβ-glucosidases to release toxic aglucones upon plant tissue damage. Such two-component plant defences are widespreadin the plant kingdom and examples of these classes of compounds are alkaloid, benzoxazinoid, cyanogenic and iridoidglucosides as well as glucosinolates and salicinoids. Conversely, many insects have evolved a diversity of counteradaptationsto overcome this type of constitutive chemical defence. Here we discuss that such counter-adaptations occurat different time points, before and during feeding as well as during digestion, and at several levels such as the insects’feeding behaviour, physiology and metabolism. Insect adaptations frequently circumvent or counteract the activity ofthe plant β-glucosidases, bioactivating enzymes that are a key element in the plant’s two-component chemical defence.These adaptations include host plant choice, non-disruptive feeding guilds and various physiological adaptations aswell as metabolic enzymatic strategies of the insect’s digestive system. Furthermore, insect adaptations often act incombination, may exist in both generalists and specialists, and can act on different classes of defence compounds. Wediscuss how generalist and specialist insects appear to differ in their ability to use these different types of adaptations:in generalists, adaptations are often inducible, whereas in specialists they are often constitutive. Future studies aresuggested to investigate in detail how insect adaptations act in combination to overcome plant chemical defences andto allow ecologically relevant conclusions.

U2 - 10.1111/brv.12066

DO - 10.1111/brv.12066

M3 - Review

VL - 89

SP - 531

EP - 551

JO - Biological Reviews

JF - Biological Reviews

SN - 1464-7931

IS - 3

ER -