Secondary metabolites in host pears defense against two fruit borers and cytochrome-P450-mediated counter-defense.

Herbivorous insects have evolved metabolic strategies to survive the challenges posed by plant secondary metabolites (SMs). This study reports an exploration of SMs present in pears, which serve as a defense against invasive Cydia pomonella and native Grapholita molesta and their counter-defense response. The feeding preferences of fruit borers are influenced by the softening of two pear varieties as they ripen. The content of SMs, such as quercetin and rutin, increases due to feeding by fruit borers. Notably, quercetin levels only increase after C. pomonella feeding. The consumption of SMs affects the growth of fruit borer population differently, potentially due to the activation of P450 genes by SMs. These two fruit borers are equipped with specific P450 enzymes that specialize in metabolizing quercetin and rutin, enabling them to adapt to these SMs in their host fruits. These findings provide valuable insights into the coevolution of plants and herbivorous insects.

Functional characterization of a novel λ-cyhalothrin metabolizing glutathione S-transferase, CpGSTe3, from the codling moth Cydia pomonella.

BACKGROUND: Recent work has shown that two codling moth (Cydia pomonella) glutathione S-transferase genes (GSTs), CpGSTd1 and CpGSTd3, can metabolize λ-cyhalothrin, one of the recommended insecticides for C. pomonella control worldwide. However, systematical characterization of delta and epsilon GSTs, especially their potential contributions in the metabolism of λ-cyhalothrin, is currently still lacking in C. pomonella. RESULTS: In this study, a total of nine cDNA sequences were identified in C. pomonella, including four in the delta and five in the epsilon subclasses. RT-qPCR showed that seven GSTs were ubiquitously expressed at all developmental stages, and CpGSTe2, CpGSTe3, and CpGSTe4 were mainly expressed in larvae. The mRNA levels of CpGSTd2, CpGSTd4, and CpGSTe5 were significantly higher in male than in female adults. Tissue-specific expression analysis revealed that the CpGSTe2, CpGSTe3, and CpGSTe4 were highly expressed in the midgut while CpGSTd2 and CpGSTd4 were predominantly expressed in the Malpighian tubules. The transcripts of these GSTs (except CpGSTe1) were co-expressed following exposure to LD10 of λ-cyhalothrin for 3 h. Recombinant CpGSTd4, CpGSTe2, and CpGSTe3 proteins expressed in Escherichia coli displayed glutathione-conjugating activity toward 1-chloro-2,4-dinitrobenzene. In addition, λ-cyhalothrin could inhibit the activity of recombinant CpGSTd4, CpGSTe2, and CpGSTe3 enzymes, but only recombinant CpGSTe3 showed λ-cyhalothrin metabolic capacity, with 21.88 ± 1.09% of parental compound being depleted within 1 h. CONCLUSION: These data show that CpGSTe3 is a third GST gene, encoding an enzyme that metabolizes λ-cyhalothrin in C. pomonella. © 2019 Society of Chemical Industry.