Molecular dissection of the Hessian fly/wheat interactions

The Hessian fly, Mayetiola destructor, is the most destructive pest of both bread and durum wheat (Triticum aestivum L. and Triticum turgidum Desf.) in the United States and also causes economic threshold level infestations in other parts of the globe. Despite its agricultural importance, scarce knowledge exists about the molecular mechanism(s) that are involved in the Hessian fly/wheat interactions. Research presented in this thesis primarily focuses on identifying midgut-expressed genes in the insect during its interaction with wheat. The first part of the thesis concentrates on the aspect of digestion and includes data on two midgut-specific serine proteases and a putative peritrophin gene. Both serine proteases were cloned from the Hessian fly via homology-based cloning, while the peritrophin gene was recovered from an expressed sequence tag (EST) project. In the second part, genes constituting detoxification and antioxidant defense were studied to validate their importance in the biology of the insect and during interaction with its host. Part three focuses on immune response genes that display differential gene expression patterns in the insect and also seem to have a role in moderating the midgut micro-flora. Part four of the thesis attempts a comparative transcriptomic approach for the salivary secretions amongst three important gall midge insect pests including the Hessian fly, the Asian rice gall midge (Orseolia oryzae) and the orange wheat blossom midge (Sitodiplosis mosellana). This study was primarily performed to reveal common expressed genes in all three insect species as well as unique genes restricted to each species. The three appendices concentrate work performed on S. mosellana