iTRAQ proteomics reveals the regulatory response to <i>Magnaporthe oryzae</i> in durable resistant vs. susceptible rice genotypes

Rice blast disease caused by Magnaporthe oryzae (M. oryzae) is one of the most serious diseases. Although previous research using two-dimensional gel-based proteomics to assess the proteins related to the rice blast resistance had been done, few proteins were identified. Here, we used the iTRAQ method to detect the differentially expressed proteins (DEPs) in the durable resistant rice variety Gangyuan8 (GY8) and the susceptible rice variety Lijiangxintuanheigu (LTH) in response to M. oryzae invasion, and then transcriptome sequencing was used to assist analysis A total of 193 and 672 DEPs were specifically identified in GY8 and LTH, respectively, with only 46 similarly expressed DEPs being shared by GY8 and LTH.39 DEPs involved in plant-pathogen interaction, plant hormone signal transduction, fatty acid metabolism and peroxisome biosynthesis were significantly different between compatible interaction (LTH) and incompatible interaction (GY8). Some proteins participated in peroxide signal transduction and biosynthesis was down-regulated in GY8 but up-regulated in LTH. A lot of genes encoding pathogenesis-related gene (PR), such as chitinase and glucanase, were significantly up-regulated at both the transcriptome and proteome levels at 24 hours post-inoculation in GY8, but up-regulated at the transcriptome level and down-regulated at the proteome level in LTH. Our study reveals that the pathogen-associated molecular pattern (PAMP)-triggered immunity defense system may be activated at the transcriptome level but was inhibited at the protein level in susceptible rice varieties after inoculation. The results may facilitate future studies of the molecular mechanisms of rice blast resistance.由稻瘟病菌（Magnaporthe oryzae，简称M. oryzae）引起的稻瘟病是最严重的作物病害之一。尽管此前已有研究利用二维凝胶蛋白质组学技术分析水稻抗稻瘟病相关蛋白，但仅鉴定出极少数蛋白。本研究采用同位素相对和绝对定量标记（iTRAQ）技术，检测持久抗病水稻品种冈优8号（GY8）与感病水稻品种丽江新团黑谷（LTH）在受稻瘟病菌侵染后的差异表达蛋白（DEPs），并辅以转录组测序进行联合分析。最终分别在GY8和LTH中特异性鉴定出193和672个差异表达蛋白，二者仅共享46个表达模式相似的差异蛋白。在亲和互作（LTH）与非亲和互作（GY8）之间，共有39个参与植物-病原体互作、植物激素信号转导、脂肪酸代谢及过氧化物酶体生物合成的差异表达蛋白存在显著表达差异。部分参与过氧化物信号转导与生物合成的蛋白在GY8中呈下调表达，而在LTH中则上调表达。在接种后24小时，GY8中大量编码病程相关基因（PR）的基因（如几丁质酶、葡聚糖酶）在转录组与蛋白质组水平均显著上调；而LTH中此类基因仅在转录组水平上调，蛋白质组水平却呈下调趋势。本研究揭示，在感病水稻品种接种稻瘟病菌后，其病原相关分子模式触发的免疫（PTI）防御系统可能在转录组层面被激活，但在蛋白质组层面受到抑制。本研究结果可为后续解析水稻抗稻瘟病的分子机制提供参考。