AUTHOR=Cui Zhongchi , Wu Wenyue , Fan Fan , Wang Fei , Liu Daqun , Di Dianping , Wang Haiyan 

TITLE=Transcriptome analysis of Lr19-virulent mutants provides clues for the AvrLr19 of Puccinia triticina

JOURNAL=Frontiers in Microbiology

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2023.1062548

DOI=10.3389/fmicb.2023.1062548

ISSN=1664-302X

ABSTRACT=<sec><title>Introduction</title><p>Wheat leaf rust caused by <italic>Puccinia triticina</italic> (<italic>Pt</italic>) remains one of the most destructive diseases of common wheat worldwide. Understanding the pathogenicity mechanisms of <italic>Pt</italic> is important to control wheat leaf rust.</p></sec><sec><title>Methods</title><p>The urediniospores of <italic>Pt</italic> race PHNT (wheat leaf rust resistance gene <italic>Lr19</italic>-avirulent isolate) were mutagenized with ethyl methanesulfonate (EMS), and two <italic>Lr19</italic>-virulent mutants named M1 and M2 were isolated. RNA sequencing was performed on samples collected from wheat cultivars Chinese Spring and TcLr19 infected with wild-type (WT) PHNT, M1, and M2 isolates at 14 days post-inoculation (dpi), respectively. Screening <italic>AvrLr19</italic> candidates by quantitative reverse transcription PCR (qPCR) and Agrobacterium-mediated transient assays in <italic>Nicotiana benthamiana</italic>.</p></sec><sec><title>Results</title><p>560 genes with single nucleotide polymorphisms (SNPs) and insertions or deletions (Indels) from non-differentially expressed genes were identified. Among them, 10 secreted proteins were screened based on their fragments per kilobase of exon model per million mapped reads (FPKM) values in the database. qPCR results showed that the expression profiles of 7 secreted proteins including PTTG_27471, PTTG_12441, PTTG_28324, PTTG_26499, PTTG_06910, PTTG_26516, and PTTG_03570 among 10 secreted proteins in mutants were significantly different with that in wild-type isolate after infection wheat TcLr19 and might be related to the recognition between <italic>Lr19</italic> and <italic>AvrLr19</italic>. In addition, a total of 216 differentially expressed genes (DEGs) were obtained from three different sample comparisons including M1-vs-WT, M2-vs-WT, and M1-vs-M2. Among 216 DEGs, 15 were predicted to be secreted proteins. One secreted protein named PTTG_04779 could inhibit programmed progress of cell death (PCD) induced by apoptosis-controlling genes B-cell lymphoma-2 associated X protein (BAX) on <italic>Nicotiana benthamiana</italic>, indicating that it might play a virulence function in plant. Taken together, total 8 secreted proteins, PTTG_04779, PTTG_27471, PTTG_12441, PTTG_28324, PTTG_26499, PTTG_06910, PTTG_26516, PTTG_03570 are identified as <italic>AvrLr19</italic> candidates.</p></sec><sec><title>Discussion</title><p>Our results showed that a large number of genes participate in the interaction between <italic>Pt</italic> and TcLr19, which will provide valuable resources for the identification of <italic>AvrLr19</italic> candidates and pathogenesis-related genes.</p></sec>