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Function of pathogenesis-related protein 10 (PR10) in soybean resistance to Asian soybean rust (ASR)

Dongfang Hu: Louisiana State University Agricultural Center

<div>ASR, which is caused by <em>Phakopsora pachyrhizi</em>, is one of the most important soybean diseases worldwide. Currently, this disease is managed through fungicide application due to the fact that all commercial soybean cultivars are susceptible to <em>P. pachyrhizi</em>. In order to develop rust-resistant commercial soybean lines, the function of the PR10 protein, which was found expressed either at higher levels or rapidly induced in resistant lines compared to susceptible ones in a time-course proteomics study, was further investigated. A short fragment of <em>PR10</em> was cloned into a <em>bean pod mottle virus</em> (BPMV) based virus induced gene silencing (VIGS) vector and introduced into soybean to suppress <em>PR10</em> expression. Rust accumulation increased 5.2 fold in two ASR resistant lines (PI417089A and PI567104B) when the <em>PR10</em> expression was suppressed by 80% through VIGS. Small RNA sequence analysis also confirmed the presence of high levels of <em>PR10</em> specific small RNAs only in soybean leaves treated with VIGS vector containing <em>RP10.</em> Meanwhile, reactive oxygen species (ROS) related microRNAs (miR408, miR398, miR2119) were highly down-regulated in the <em>PR10</em> silenced leaf samples. <em>PR10</em> silenced soybean leaves also produced less ROS after rust inoculation when stained with 3,3’-diaminobenzidine (DAB). These results indicate a direct function of PR10 in conferring ASR resistance possibly through enhancing the production of ROS at the site of rust infection.</div>