Cytological and molecular characterization of non-host resistance in Arabidopsis thaliana against wheat stripe rust.

Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most destructive diseases of wheat worldwide. We report the use of the non-host plant Arabidopsis thaliana to identify the basis of resistance to Pst at the cytological and molecular levels. No visible symptoms were observed on Arabidopsis leaves inoculated with Pst. Microscopic observations showed that significantly reduced numbers of Pst urediospores had successfully achieved penetration in Arabidopsis compared with those in wheat. There were significant differences in the frequency of stomatal penetration but not in fungal growth among different Pst races in Arabidopsis. The fungus failed to successfully form haustoria in Arabidopsis and attempted infection induced an active response including accumulation of phenolic compounds and callose deposition in plant cells. A set of defence-related genes were also up regulated during the Pst infection. Compared with wild type plants, increased fungal growth was observed in an npr1-1 mutant and in NahG transformed plants, which both are insensitive to salicylic acid. However, treatment of Arabidopsis plants with cytochalasin B, an inhibitor of actin microfilament polymerization, did not increase susceptibility to Pst. Our results demonstrate that Arabidopsis can be used to study mechanisms of non-host resistance to wheat stripe rust, and highlight the significance of participation of salicylic acid in non-host resistance to rust fungi.