Analyzing Molecular Bases of Heat-Induced Loss of Wheat Resistance to Hessian Fly Infestation Using RNA-Sequencing

"Heat stress compromises resistance of wheat to Hessian fly (HF, Mayetiola destructor). The objective of our research is to analyze the molecular bases of heat-induced loss of wheat resistance to HF infestation using RNA Sequencing (RNA-Seq). A wheat cultivar 'Molly' containing a resistance gene (R-gene) H13 was infested by an avirulent HF biotype GP. Molly is resistant to biotype GP under temperature below 20°C, but becomes susceptible at higher temperatures. The infested and uninfested Molly wheat was treated with 35°C for 6 h. RNA-sequencing (RNA-seq) approach was used to analyze differentially expressed genes (DEGs) on samples collected from HF feeding site tissue in wheat plants. In the current study, we identified 21 early resistant responsive (ERR) genes in wheat plants, of which six are downregulated by heat stress in the presence of HF. We also found that heat stress largely downregulated primary and secondary metabolisms of wheat plants and exert significant impact on phytohormone metabolism. Our results suggest that heat stress compromises wheat resistance to HF infestation by suppressing expression of ERR genes, remodeling plants primary metabolism and secondary metabolisms in a way that slow down or prevent swift mobilization of resources in wheat plants to produce defense-related compounds. Additionally, 2-oxo-phytodienoic acid (OPDA) signaling may be critical to wheat resistance. Heat stress likely prevents the accumulation of OPDA by upregulation 12-oxo-phytodienoic acid reductase (OPR) that converts OPDA."