Insect resistance of transgenic tobacco expressing an insect chitinase gene |
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Authors: | Ding Xiongfei Gopalakrishnan Bhuvana Johnson Lowell B White Frank F Wang Xiaorong Morgan Thomas D Kramer Karl J Muthukrishnan Subbaratnam |
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Institution: | (1) Department of Plant Pathology, Kansas State University, Throckmorton Hall, Manhattan, USA;(2) Department of Biochemistry, Kansas State University, Willard Hall, Manhattan, USA;(3) US Department of Agriculture, US Grain Marketing Research Laboratory, Agricultural Research Service, Manhattan, USA |
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Abstract: | Chitinase expression in the insect gut normally occurs only during moulting, where the chitin of the peritrophic membrane is presumably degraded. Thus, insects feeding on plants that constitutively express an insect chitinase gene might be adversely affected, owing to an inappropriately timed exposure to chitinase. This hypothesis was tested by introducing a cDNA encoding a tobacco hornworm (Manduca sexta) chitinase (EC 3.2.1.14) into tobacco via Agrobacterium tumefaciens-mediated transformation. A truncated but enzymatically active chitinase was present in plants expressing the gene. Segregating progeny of high-expressing plants were compared for their ability to support growth of tobacco budworm (Heliothis virescens) larvae and for feeding damage. Both parameters were significantly reduced when budworms fed on transgenic tobacco plants expressing high levels of the chitinase gene. In contrast, hornworm larvae showed no significant growth reduction when fed on the chitinase-expressing transgenics. However, both budworm and hornworm larvae, when fed on chitinase-expressing transgenic plants coated with sublethal concentrations of a Bacillus thuringiensis toxin, were significantly stunted relative to larvae fed on toxin-treated non-transgenic controls. Foliar damage was also reduced. Plants expressing an insect chitinase gene may have agronomic potential for insect control |
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Keywords: | Bacillus thuringiensis toxin Heliothis virescens Manduca sexta Nicotiana tabacum tobacco budworm tobacco hornworm chitinase |
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