Insect Science 13, 339-348 Hessian fly genes encoding small secreted gut proteins 339 Correspondence: Ming-Shun Chen, Department of Entomology, Kansas State University, 123 Waters Hall, Manhattan, KS 66506. Tel: 785 532 4719; fax: 785 532 6232; email: mchen@ksu.edu Genes encoding a group of related small secreted proteins from the gut of Hessian fly larvae [Mayetiola destructor (Say)] Abstract A group of related genes has been isolated and characterized from the gut of Hessian fly larvae [Mayetiola destructor (Say)]. Members in this group appear to encode proteins with secretary signal peptides at the N-terminals. The mature putative proteins are small, acidic proteins with calculated molecular masses of 14.5 to 15.3 kDa, and isoelectric points from 4.56 to 4.88. Northern blot analysis revealed that these genes are expressed predominantly in the gut of Hessian fly larvae and pupae. Two related genes, G10K1 and G10K2, were isolated as tandem repeats. Both genes contain three exons and two introns. The intron/exon boundaries were conserved in terms of amino acid encoding, suggesting that they arose by gene duplication. The fact that the frequency of this group of clones in a gut cDNA library higher than that of total cDNA clones encoding digestive enzymes suggested that this group of proteins may perform an important function in the gut physiology of this insect. However, the exact functions of these proteins are as yet known since no sequence similarity could be identified between these proteins and any known sequences in public databases using standard methods. Key words Hessian fly, gut, Mayetiola destructor, secreted protein, wheat DOI 10.1111/j.1744-7917.2006.00102.x MING-SHUN CHEN 1,2 , XIANG LIU 2 , YU-CHENG ZHU 3 , JOHN C. REESE 2 and GERALD E. WILDE 2 1 USDA-ARS, Plant Science and Entomology Research Unit, 2 Department of Entomology, Kansas State University, Manhattan, Kansas, and 3 USDA-ARS-JWDSRC, Stoneville, Minnesota, USA Introduction The Hessian fly [Mayetiola destructor (Say)] is one of the most destructive pests of wheat (Triticum aestivum L.) in North America, South Europe, North Africa, and Central Asia. In the US, this insect can cause annual losses of up to 5%-10% of the wheat crop of US farmers (Hatchett et al., 1987; Buntin, 1999). Historically, host plant resistance genes in wheat are the most effective and cost-efficient way to control this pest (Hatchett & Gallun, 1970; Ratcliffe & Hatchett, 1997). However, the success of this strategy is challenged by the ability of the Hessian fly to constantly develop populations virulent to host resistance genes after their deployment. So far, 32 resistance genes have been identified (Ratcliffe & Hatchett, 1997; Martin-Sanches et al., 2003; Williams et al., 2003; Sardesai et al., 2005). However, for many of the known resistance genes, a virulent biotype can be found in field populations (Ratcliffe et al., 1994, 2000). At least four resistant cultivars carrying five resistance genes (H3, H5, H6, and a combination of H7H8) no longer confer an effective level of resistance. To safeguard future success in managing this destructive pest, we need to identify alternatives to the traditional host- resistance strategy for controlling this pest. The Hessian fly larva is the only stage that causes damage to wheat plants. The larva lives between leaf- sheaths at the base like a parasite and sucks juice from the plant (Haseman, 1930; Hatchett et al., 1990). Since the gut of many major agricultural insect pests is also the target for