Dataset Information

Evolution of Asian Corn Borer Resistance to Bt Toxins Used Singly or in Pairs.

ABSTRACT: Transgenic crops producing insecticidal proteins from Bacillus thuringiensis (Bt) have revolutionized pest control, but the benefits of this approach have been reduced by the evolution of resistance in pests. The widely adopted 'pyramid strategy' for delaying resistance entails transgenic crops producing two or more distinct toxins that kill the same pest. The limited experimental evidence supporting this strategy comes primarily from a model system under ideal conditions. Here we tested the pyramid strategy under nearly worst-case conditions, including some cross-resistance between the toxins in the pyramid. In a laboratory selection experiment with an artificial diet, we used Bt toxins Cry1Ab, Cry1F, and Cry1Ie singly or in pairs against Ostrinia furnacalis, one of the most destructive pests of corn in Asia. Under the conditions evaluated, pairs of toxins did not consistently delay the evolution of resistance relative to single toxins.

SUBMITTER: Wang Y

PROVIDER: S-EPMC6723947 | biostudies-literature | 2019 Aug

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Evolution of Asian Corn Borer Resistance to Bt Toxins Used Singly or in Pairs.

Wang Yueqin Y Quan Yudong Y Yang Jing J Shu Changlong C Wang Zhenying Z Zhang Jie J Gatehouse Angharad M R AMR Tabashnik Bruce E BE He Kanglai K

Toxins 20190806 8

Transgenic crops producing insecticidal proteins from <i>Bacillus thuringiensis</i> (Bt) have revolutionized pest control, but the benefits of this approach have been reduced by the evolution of resistance in pests. The widely adopted 'pyramid strategy' for delaying resistance entails transgenic crops producing two or more distinct toxins that kill the same pest. The limited experimental evidence supporting this strategy comes primarily from a model system under ideal conditions. Here we tested ...[more]

PMID: 31390820

Similar Datasets

Project description:The Asian corn borer, Ostrinia furnacalis, is a serious insect pest that can infest corn leaves and stems. Due to its internal feeding behavior, its larvae are not exposed to insecticides that are usually sprayed for pest control. To minimize crop damage caused by O. furnacalis, improving insect resistance trait of corn has been considered as an optimal control tactic. This study screened 27 corn varieties for their insect resistance trait and selected three varieties of Ilmichal (IM), P3394, and Kwangpyeongok (KP) that showed insect resistance trait. O. furnacalis larvae did not show any significant difference in preference between these three insect-resistant corn varieties and a control susceptible variety. However, these resistant varieties after ingestion significantly interfered with larval development of O. furnacalis. This suggests that the insect resistance trait is induced by antibiosis, but not by antixenosis. Indeed, larvae fed with these varieties suffered from low chymotrypsin (CHY) activities in the midgut juice. To determine the target CHY inhibited by resistant corn varieties, a total of nine CHY genes (Of-CHY1~Of-CHY9) were predicted from the transcriptome of O. furnacalis. Six genes (Of-CHY1~Of-CHY6) were expressed in all developmental stages and tissues. Especially, Of-CHY3 was highly expressed in the midgut of O. furnacalis larvae. RNA interference (RNAi) using double-stranded RNA (dsRNA) specific to Of-CHY3 (2 μg of dsRNA injected to each L5 larva) resulted in significant reduction of Of-CHY3 expression level at 24 h post-treatment. Feeding L3 larvae with this dsRNA also significantly suppressed the expression level of Of-CHY3 and reduced its enzyme activity at 24 h post-treatment. A recombinant Escherichia coli expressing dsRNA specific to Of-CHY3 was constructed using L4440 vector. Feeding such recombinant bacteria suppressed the expression level of Of-CHY3 and prevented larval development of O. furnacalis. These results suggest that the three resistant varieties can produce a resistance factor(s) to inhibit the CHY activity of O. furnacalis and suppress larval growth. This study suggests that CHY might be an inhibition target in O. furnacalis for breeding insect-resistant corns.

Project description:We assessed the effectiveness of a biofortified maize line (4BtxHC) which accumulates high levels of antioxidant carotenoids that also expressed the insecticidal Cry1Ac Bacillus thuringiensis (Bt) gene against the European corn borer Ostrinia nubilalis. This line had been previously engineered to accumulate carotenoids specifically in the seed endosperm, whereas the Bt gene was expressed constitutively. The concentrations of Bt toxin (Cry 1Ac) in the leaves of the 4Bt and 4BtxHC lines were not significantly different at 47±6 μg/g of fresh weight (FW); neither were they in the kernels of both lines (35±3 μg/g FW). The kernels and leaves were toxic to the larvae of O. nubilalis. However, the insecticidal activity was substantially lower (ca. 20%) than that of lines that expressed only Bt in spite that the two lines showed a quantity of toxin not significantly different in kernels or in leaves. Although the reduced effectiveness of Cry1Ac in kernels may not be entirely surprising, the observation of the same phenomenon in vegetative tissues was unexpected. When semi-artificial diets containing kernels from 4Bt supplemented with different levels of β-carotene were used in insect bioassays, the β-carotene moderated the effectiveness of the Bt similarly to the plant material with carotenoid enrichment. To elucidate the biochemical basis of the reduced effectiveness of Bt toxin in the carotenoid-enriched plants, we measured the activity of three enzymes known to be implicated in the detoxification defence, namely, catalase, superoxide dismutase and glutathione S-transferase. Whereas Cry1Ac expression significantly increased SOD and CAT enzymatic activity in the absence of carotenoids, carotenoids, either in 4BtxHC or in artificial diets enriched with β-carotene, significantly lowered CAT activity. Carotenoids can therefore moderate the susceptibility of the maize borer O. nubilalis to Cry1Ac, and we hypothesize that their role as antioxidants could explain this phenomenon via their scavenging of reactive oxygen species produced during Cry1Ac detoxification in the larvae. The involvement of this mechanism in the decreased mortality caused by Cry1Ac when carotenoids are present in the diet is discussed.

Dataset Information

Evolution of Asian Corn Borer Resistance to Bt Toxins Used Singly or in Pairs.

Publications

Evolution of Asian Corn Borer Resistance to Bt Toxins Used Singly or in Pairs.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets