Submitted to: Journal of Chemical Ecology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/20/2007
Publication Date: 11/16/2007
Citation: Liu, X., Bai, J., Zhu, L., Liu, X., Weng, N., Reese, J.C., Harris, M., Stuart, J.J., Chen, M. 2007. Differential Gene Expression of H9 and H13 Wheat Genotypes during Attack by Virulent and Avirulent Hessian Fly (Mayetiola destructor) Larvae. Journal of Chemical Ecology. 33:2171-2194. 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 the host plant resistance strategy is that resistance conferred by R-genes is short lived, lasting for about 6 to 8 years. Therefore, new strategies for durability should be explored. This objective of this research is to examine gene expression in resistant and susceptible plants and to identify potential genes that might provide durable resistance. A large number of genes (1119) were found expressed differently between resistant and susceptible wheat seedlings. We are currently studying the roles of these differentially expressed genes in host plant resistance.
Technical Abstract: Wheat and its relatives possess large numbers of resistance genes (R-genes) specific for Hessian fly (HF) [Mayetiola destructor (Say)], an insect that manipulates its host by establishing a nutritive feeding tissue. Many R-genes confer complete resistance to the Hessian fly, i.e. 100% of attacking larvae die within days of initial attack. To counteract this type of resistance, Hessian fly has the ability to differentiate and maintain population heterogeneity, i.e. different genotypes (also referred to as biotypes phenotypically) that can overcome resistance conferred by specific R-genes. The objective of this study was to use the wheat-HF system to study the molecular interactions between host plants and insects. Using two different R-genes, H9 and H13, a genome-wide transcriptional analysis was performed to determine gene expression during two types of interactions: incompatible (R-gene + avirulent larvae) and compatible (R-gene + virulent larvae). A large number of transcripts (1,119) showed significant alterations in gene expression during either compatible or incompatible interactions. Analysis of the genes with known functions revealed that the genes encoding proteins involved in direct defense and the genes encoding enzymes involved in the phenylpropanoid, cell wall, and lipid metabolism pathways, were the major targets for differential regulation during compatible and incompatible interactions. Thus a combination of the enhancement of antibiosis defense, the evasion of nutrient metabolism induction, and the fortification and expansion of the cell wall, are likely the collective mechanism for host plant resistance observed during incompatible interactions. To overcome this resistance, virulent larvae appeared to suppress antibiosis defense, while inducing nutrient metabolism, weakening cell wall, and inhibiting plant growth.