The hypersensitive induced reaction 3 ( HIR 3 ) gene contributes to plant basal resistance via an EDS 1 and salicylic acid‐dependent pathway

Summary The hypersensitive‐induced reaction ( HIR ) gene family is associated with the hypersensitive response ( HR ) that is a part of the plant defense system against bacterial and fungal pathogens. The involvement of HIR genes in response to viral pathogens has not yet been studied. We now report that the HIR 3 genes of Nicotiana benthamiana and Oryza sativa (rice) were upregulated following rice stripe virus ( RSV ) infection. Silencing of HIR 3 s in N. benthamiana resulted in an increased accumulation of RSV RNA s, whereas overexpression of HIR 3s in N. benthamiana or rice reduced the expression of RSV RNA s and decreased symptom severity, while also conferring resistance to Turnip mosaic virus , Potato virus X , and the bacterial pathogens Pseudomonas syringae and Xanthomonas oryzae . Silencing of HIR 3 genes in N. benthamiana reduced the content of salicylic acid ( SA ) and was accompanied by the downregulated expression of genes in the SA pathway. Transient expression of the two HIR 3 gene homologs from N. benthamiana or the rice HIR 3 gene in N. benthamiana leaves caused cell death and an accumulation of SA, but did not do so in EDS 1 ‐silenced plants or in plants expressing NahG . The results indicate that HIR 3 contributes to plant basal resistance via an EDS 1 ‐ and SA‐dependent pathway.