The effector repertoire of Puccinia striiformis subdues host-plant immunity

Rust outbreaks cause severe yield lossespose a serious threat to global food security. As biotrophic pathogens, rust fungi produce effectors to suppress host immunity. In this study, we used a systemic approach to identify and characterize effectors in Puccinia striiformis f. sp. tritici. Among secreted proteins encoded by the Pst genome, we identified 150 putative effectors that are Cys-rich or up-regulated during hostinfection. A systematic screen showed that 14 of them suppressed programmed cell death (PCD) triggered by BAX and INF1 in Nicotiana benthamiana, and all have high intra- and inter-species polymorphisms at the protein level. Although these 14 effectors individually made only minor contributions to Pst virulence, delivery of them into wheat plants via a bacterial type-III secretion system efficiently suppressed PTI and ETI. Interestingly, three of them, Pst_4941, Pst_4884, and Pst_5578, triggered HR-like PCD in the AvSYr1NIL, but only Pst_4941 also caused PCD in the AvSYr7 NIL, suggesting that they may function as avirulence factors. This study suggests that Pst effectors function to suppress PTI and ETI.

State Key Laboratory of Crop Stress Biology for Arid Areas and College of Agronomy, Northwest A&F University, P. R. China
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