Submitted to: Annals of the Entomological Society of America
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/7/2004
Publication Date: 11/1/2004
Citation: Yoshyiama, M., Shukle, R.H. 2004. Molecular cloning and characterization of a glutathione s-transferase gene from hessian fly (diptera: cecidomyiidae). Annals of the Entomological Society of America. 97(6):1285-1293. Interpretive Summary: Hessian flies pose a significant economic threat to wheat in terms of reduced grain yield, particularly in the eastern soft winter wheat region of the United States. The use of wheat resistant to Hessian flies has proven to be the most economically and environmentally sound method of control for this pest. However, the widespread use of resistant wheat has lead to the emergence of more virulent forms or 'biotypes' of the pest that can survive on formerly resistant wheat. The development of these more virulent biotypes is the greatest threat to the continued protection of wheat, and little is known about how the pest overcomes defense reactions in wheat. Plant-eating insects derive protection against toxic plant compounds by having a complex of general-purpose defensive enzymes to overcome toxins in the plants they eat. We have identified and characterized the DNA of a gene for such a general-purpose defensive enzyme from the Hessian fly. The gene we have identified can be important in the way Hessian fly larvae survive on wheat. Knowledge about genes the Hessian fly uses to survive on wheat will aid scientists seeking to develop new and more effective resistant wheat to protect the crop in the United States. This will benefit wheat producers in terms of enhanced and more economical pest control as well as increased grain production.
Technical Abstract: Hessian flies pose a significant economic threat to wheat in terms of reduced grain yield, particularly in the eastern soft winter wheat region of the United States. However, little is known about the molecular mechanisms involved in this plant-insect interaction. Insect herbivores derive important protection against potentially toxic plant allelochemicals by having a complex of general-purpose defensive enzymes to overcome the potential toxicity of plants they eat. Glutathione S-transferases (GSTs) are enzymes involved in the detoxification of many xenobiotics such as plant defense allelochemicals as well as antioxidative defense against the prooxidative toxicity of allelochemicals. We have cloned and characterized two GST genes from biotype GP of the Hessian fly. Sequence analysis and homology searches of the coding region for the first gene (designated MdGST1) indicated that it contained an intact coding region for a GST-like protein. Analysis of the coding region for the second gene indicated that it contained numerous stops and was a pseudogene. Expression of the GST-like protein from MdGST1 in Escherichia coli and analysis of activity by measuring conjugation of reduced glutathione to the GST substrate 1-chloro-2,4-dinitrobenzene confirmed GST activity for the protein encoded by MdGST1. RT-PCR revealed that the MdGST1 gene was expressed in midgut tissue, fat body, and salivary glands of Hessian fly larvae. The potential role of GSTs in the plant-insect interaction is discussed. Future work assessing GST expression during the plant-insect interaction and the use of double-stranded RNA interference (dsRNAi) to address the function of GSTs in the interaction are planned.