ARS | Publication request: Analysis of Transcripts and Proteins Expressed in the Salivary Glands of Hessian Fly (Mayetiola destructor) Larvae

Submitted to: Journal of Insect Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 8, 2007
Publication Date: January 1, 2008
Citation: Chen, M., Huixian, Z., Zhu, Y., Scheffler, B.E., Liu, X., Liu, X., Hulbert, S., Stuart, J. 2008. Analysis of Transcripts and Proteins Expressed in the Salivary Glands of Hessian Fly (Mayetiola destructor) Larvae. Journal of Insect Physiology.54:1-16.

Interpretive Summary: The Hessian fly (Mayetiola destructor) is one of the most destructive insects of wheat. The insect is currently controlled almost exclusively by host plant resistance. The challenge for host plant resistance is that Hessian fly constantly develops new biotypes that overcome resistance of deployed cultivars. To generate durable resistant wheat plants, we need to understand how new biotypes are being developed. The objective of this research is to analyze the genes expressed in the salivary glands of Hessian fly larvae, and the proteins that are likely injected into host plants. The proteins injected into host plants are likely important for insect biotype development. This research identified a large number of genes encoding proteins that are likely injected into wheat tissues. The super-diversity and fast evolution of these genes are consistent with rapid biotype development of the insect. This research provides a foundation for future research to reveal the mechanism of biotype development.

Technical Abstract: Hessian fly (HF) (Mayetiola destructor) larvae are thought to manipulate host growth and metabolism through salivary secretions. However, the transcriptome and proteome of HF salivary glands have not been systematically analyzed. In this research, we analyzed Expressed-Sequence-Tags (EST) representing 6,106 cDNA clones randomly selected from four libraries made from dissected salivary glands. We also analyzed the protein composition of dissected salivary glands using one- and two-dimensional gel electrophoresis as well as LC-MS/MS analysis. Transcriptomic analysis revealed that approximately 60% of the total cDNA clones and 40% of assembled uni-sequences encoded secretory proteins (SP). The SP-encoding cDNAs were grouped into superfamilies and families according to sequence similarities. In addition to the high percentage of SP-encoding transcripts, there was also a high percentage of transcripts encoding proteins that were either involved directly in protein synthesis or in house-keeping functions that provide conditions necessary for protein synthesis. Proteomic analysis also revealed a high percentage of proteins involved in protein synthesis either directly or indirectly. The high percentage of SP-encoding transcripts and high percentage of proteins related to protein synthesis suggested that the salivary glands of HF larvae are indeed specialized tissues for synthesis of proteins for host injection. However, LC-MS/MS analysis of 64 proteins did not identify any SPs corresponding to the cDNA sequences. The lack of accumulation of SPs in the salivary glands indicated the SPs were likely secreted as soon as they were synthesized.