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Title: Cadherin is a functional receptor of bacillus thuringiensis toxin Cry2Aa in the beet armyworm, spodoptera exigua

Author
item QUI, L - Huazhong Agricultural University
item HOU, L - Huazhong Agricultural University
item ZHANG, B - Huazhong Agricultural University
item LIU, L - Huazhong Agricultural University
item LI, B - Huazhong Agricultural University
item DENG, P - Huazhong Agricultural University
item MA, W - Huazhong Agricultural University
item WANG, X - Huazhong Agricultural University
item Fabrick, Jeffrey
item CHEN, L - Huazhong Agricultural University
item LEI, C - Huazhong Agricultural University

Submitted to: Journal of Invertebrate Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/27/2015
Publication Date: 3/6/2015
Publication URL: http://handle.nal.usda.gov/10113/61066
Citation: Qui, L., Hou, L., Zhang, B., Liu, L., Li, B., Deng, P., Ma, W., Wang, X., Fabrick, J.A., Chen, L., Lei, C. 2015. Cadherin is a functional receptor of bacillus thuringiensis toxin Cry2Aa in the beet armyworm, spodoptera exigua. Journal of Invertebrate Pathology. 127:47-53.

Interpretive Summary: Several protein toxins from the bacterium Bacillus thuringiensis (Bt) are used in transgenic Bt crops to control a variety of insect pests while having little or no impact on non-target insects or other plants or animals. Development of resistance to the toxins commonly used in Bt crops would jeopardize the usefulness of these important management tools. Because different Bt toxins normally associate with different targets, or receptors, in the insect gut, the current strategy to avoid or delay resistance is to “pyramid” two or more Bt toxins in the same plant. In cotton, the most commonly pyramided toxins are Cry1A and Cry2A. An ARS scientist at Maricopa, AZ and collaborators showed that both Cry1A and Cry2A associate with the same target receptor (a cadherin protein) in the gut of the beet armyworm, which is an important pest worldwide. Suppression of this cadherin reduced suceptibility of beet armyworm catepillars to the two Bt toxins. These results indicate that a single cadherin protein can serve as the receptor for more than one Bt toxin, suggesting that in at least some cases the strategy of pyramiding Bt toxins may not prevent the development of resistance to Bt crops.

Technical Abstract: Bacillus thuringiensis (Bt) insecticidal crystal (Cry) proteins are effective against some insect pests in sprays and transgenic crops, although the evolution of resistance could threaten the long-term efficacy of such Bt use. One strategy to delay resistance to Bt crops is to “pyramid” two or more Bt proteins that bind to distinct receptor proteins within the insect midgut. The most common Bt pyramid in cotton (Gossypium hirsutum L.) employs Cry1A with Cry2A to target several key lepidopteran pests, including the beet armyworm, Spodoptera exigua (Hubner), which is a serious migratory pest of many vegetable crops and is increasingly important in cotton in China. While cadherin and aminopeptidase-N are key receptors of Cry1 toxins in many lepidopterans including S. exigua, the receptor for Cry2A remains poorly characterized. Here, we show that a heterologous expressed peptide corresponding to cadherin repeat 7 to the membrane proximal extracellular domain (CR7-MPED) in the S. exigua cadherin 1b (SeCad1b) binds Cry1Ac and Cry2Aa. Moreover, SeCad1b transcription was suppressed in S. exigua larvae by oral RNA interference and susceptibility to Cry1Ac and Cry2Aa was significantly reduced. These results indicate that SeCad1b functions as a receptor of both Cry1Ac and Cry2Aa, having major implications for resistance management for S. exigua in Bt crops.