Revealing Differentially Expressed Genes and Identifying Effector Proteins of Puccinia striiformis f. sp. tritici in Response to High-Temperature Seedling Plant Resistance of Wheat Based on Transcriptome Sequencing

Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most important diseases of wheat (Triticum aestivum L.) globally. Recently, more aggressive Pst races have evolved to acquire new virulence profiles and are adapted better to high temperature than most of the previous races. Breeding cultivars with durable high-temperature seedling-plant (HTSP) resistance is an important strategy for controlling stripe rust. Understanding the mechanism of wheat HTSP resistance against Pst is important for more efficient breeding to improve host resistance. In the present study, transcriptomic analysis identified 25 Pst differentially expressed genes (DEGs) that were involved in the HTSP resistance in wheat cultivar Xiaoyan6 (XY6). Functional annotation indicated that these DEGs are related to membrane proteins, mRNA binding proteins, cell membrane transporters, and synthesis of cell nitrogen compounds. Among these DEGs, a candidate effector, PstCEP1 (PSTG_13342), was identified and cloned, and its function was verified. Barley stripe mosaic virus (BSMV)-mediated host-induced gene silencing (HIGS) of PstCEP1 reduced Pst virulence. Signal peptide verification and functional testing in Nicotiana benthamiana indicated that PstCEP1 is a secreted protein and has the function of suppressing programmed cell death (PCD). PstCEP1 as a candidate effector was further supported by type three secretion system (TTSS)-mediated overexpression responding to wheat HTSP resistance via affecting the pathogen-associated molecular pattern (PAMP)-triggered immunity (PTI) and effector-triggered immunity (ETI). IMPORTANCE In the present study, we performed transcriptomic analysis to identify differentially expressed genes and effector proteins of Puccinia striiformis f. sp. tritici (Pst) in response to the high-temperature seedling-plant (HTSP) resistance in wheat. Experimental validation confirmed the function of the highest upregulated effector protein, PstCEP1. This study provides a key resource for understanding the biology and molecular basis of Pst responses to wheat HTSP resistance, and PstCEP1 may be used in future studies to understand pathogen-associated molecular pattern-triggered immunity and effector-triggered immunity processes in the Pst-wheat interaction system.