Wheat hypersensitive-induced reaction genes TaHIR1 and TaHIR3 are involved in response to stripe rust fungus infection and abiotic stresses.

KEY MESSAGE : TaHIR1 and TaHIR3 play positive roles in resistance to the stripe rust fungus via inducing HR and regulating defense-related genes, but are negatively regulated by various abiotic stimuli. Plant hypersensitive-induced reaction (HIR) genes are known to be associated with the hypersensitive response and disease defense. In wheat, two HIR genes, TaHIR1 and TaHIR3, have been identified and found to be up-regulated after infection with the stripe rust fungus. Here, we further determined their roles in defense against abiotic stresses and the stripe rust pathogen, Puccinia striiformis f. sp. tritici. TaHIR1 and TaHIR3 proteins were localized in the plasma membrane of tobacco cells. The expression of TaHIR1 and TaHIR3 was reduced by the environmental stimuli, including low temperature, drought, and high salinity stresses. In addition, the expression of TaHIR1 and TaHIR3 was down-regulated by exogenously applied ethrel and abscisic acid, whereas expression was not affected by treatments with salicylic acid and methyl jasmonate. Furthermore, barley stripe mosaic virus-induced gene silencing of TaHIR1 and TaHIR3 reduced resistance in wheat cultivar Suwon11 against an avirulent stripe rust pathotype CYR23 and area of necrotic cells neighboring the infection sites, and altered the expression levels of defense-related genes. These results suggest that TaHIR1 and TaHIR3 function positively in the incompatible interaction of wheat-stripe rust fungus, but exhibit negative transcriptional response to abiotic stresses.