Comparative proteomic analysis of susceptible and resistance maize lines to southern corn rust

Southern corn rust (SCR) is one of destructive diseases in maize caused by Puccinia polysora Undrew. (P. polysara), widely occurring in warm-temperate and tropical regions globally. To identify candidate SCR resistance-related proteins and understand the molecular mechanism underlaying the maize and P. polysara interaction, comparative proteomic analysis of susceptible and resistance maize lines was performed. A total of 6,612 proteins were successfully identified using an iTRAQ-based proteomic approach. Fold changes and statistical analysis demonstrated that 687 proteins increased and 802 proteins decreased in the resistant line, while 571 increased and 464 decreased in the susceptible line. One remorin protein, namely ZmREM1.3 (B4G1B0), was significantly induced by SCR in the resistant genotype, while decreased in susceptible genotype after P. polysara infection. Plant-specific remorin proteins have been shown to play important roles during microbial infection and plant signaling processes. Transgenic analysis showed that overexpression of ZmREM1.3 in maize confers enhanced resistance to the biotrophic fungal pathogen SCR. Upon pathogen challenge, the ZmREM1.3-overexpressing plants accumulated higher levels of defense hormones, SA and JA. Moreover, stronger induction of defense gene expression was also observed in ZmREM1.3-overexpressing maize plants in response to SCR infection. Taken together, our results support that ZmREM1.3 plays a positive role in regulating the maize defense against SCR likely through SA/JA-mediated defense signaling pathways. This is the first attempt for large scale analysis of the molecular mechanisms underlaying the maize and P. polysara interaction at the proteomic level, and the first evidence for remorin protein family in resistant to fungal disease.南方玉米锈病（Southern corn rust, SCR）是由多堆柄锈菌（Puccinia polysora Undrew，P. polysora）引起的毁灭性玉米病害之一，在全球暖温带与热带区域广泛发生。为鉴定与SCR抗病相关的候选蛋白，并解析玉米与多堆柄锈菌互作的分子机制，本研究对感病及抗病玉米品系开展了比较蛋白质组学分析。采用基于同位素相对与绝对定量标记（iTRAQ）的蛋白质组学方法，共成功鉴定到6612种蛋白质。通过倍数变化分析与统计学检验，抗病品系中共有687种蛋白质表达上调、802种下调；而感病品系中上调与下调的蛋白质分别为571种与464种。本研究发现，一类瑞莫林蛋白（remorin）ZmREM1.3（B4G1B0）在抗病基因型中被SCR显著诱导表达，但在感病基因型受多堆柄锈菌侵染后其表达量显著下调。植物特异性瑞莫林蛋白已被证实可在微生物侵染及植物信号转导过程中发挥重要功能。转基因功能验证结果表明，在玉米中过表达ZmREM1.3可显著增强其对活体营养型真菌病原物SCR的抗性。在病原物侵染后，过表达ZmREM1.3的玉米植株体内防御激素水杨酸（SA）与茉莉酸（JA）的积累水平显著升高。此外，过表达ZmREM1.3的玉米植株在受SCR侵染时，其防御基因的表达也被更强地诱导。综上，本研究结果证实ZmREM1.3通过水杨酸/茉莉酸介导的防御信号通路，正向调控玉米对SCR的防御反应。本研究首次在蛋白质组学层面大规模解析了玉米与多堆柄锈菌的互作分子机制，同时也为瑞莫林蛋白家族参与抗真菌病害提供了首个实验证据。