Transcriptome Analysis of H2O2-Treated Wheat Seedlings Reveals a H2O2-Responsive Fatty Acid Desaturase Gene Participating in Powdery Mildew Resistance

Hydrogen peroxide (H2O2) plays important roles in plant biotic and abiotic stress responses. However, the effect of H2O2 stress on the bread wheat transcriptome is still lacking. To investigate the cellular and metabolic responses triggered by H2O2, we performed an mRNA tag analysis of wheat seedlings under 10 mM H2O2 treatment for 6 hour in one powdery mildew (PM) resistant (PmA) and two susceptible (Cha and Han) lines. In total, 6,156, 6,875 and 3,276 transcripts were found to be differentially expressed in PmA, Han and Cha respectively. Among them, 260 genes exhibited consistent expression patterns in all three wheat lines and may represent a subset of basal H2O2 responsive genes that were associated with cell defense, signal transduction, photosynthesis, carbohydrate metabolism, lipid metabolism, redox homeostasis, and transport. Among genes specific to PmA, ‘transport’ activity was significantly enriched in Gene Ontology analysis. MapMan classification showed that, while both up- and down- regulations were observed for auxin, abscisic acid, and brassinolides signaling genes, the jasmonic acid and ethylene signaling pathway genes were all up-regulated, suggesting H2O2-enhanced JA/Et functions in PmA. To further study whether any of these genes were involved in wheat PM response, 19 H2O2-responsive putative defense related genes were assayed in wheat seedlings infected with Blumeria graminis f. sp. tritici (Bgt). Eight of these genes were found to be co-regulated by H2O2 and Bgt, among which a fatty acid desaturase gene TaFAD was then confirmed by virus induced gene silencing (VIGS) to be required for the PM resistance. Together, our data presents the first global picture of the wheat transcriptome under H2O2 stress and uncovers potential links between H2O2 and Bgt responses, hence providing important candidate genes for the PM resistance in wheat.过氧化氢（Hydrogen peroxide, H₂O₂）在植物生物与非生物胁迫响应中发挥重要作用。然而目前关于H₂O₂胁迫对普通小麦转录组的影响仍缺乏系统研究。为探究H₂O₂诱导的细胞与代谢响应，本研究对1个抗白粉病（powdery mildew, PM）材料PmA以及2个感病材料Cha和Han的小麦幼苗，施加10 mM H₂O₂处理6小时后开展了mRNA标签分析。最终分别在PmA、Han与Cha中鉴定出6156、6875和3276个差异表达转录本。其中，260个基因在3个小麦材料中均呈现一致的表达模式，可作为基础H₂O₂响应基因子集，这些基因涉及细胞防御、信号转导、光合作用、碳水化合物代谢、脂质代谢、氧化还原稳态及物质转运等生物学过程。在PmA特异性表达的基因中，基因本体（Gene Ontology, GO）富集分析显示“物质转运”活性条目显著富集。MapMan分类分析显示：尽管生长素、脱落酸及油菜素内酯的信号通路基因同时存在上调与下调表达，但茉莉酸与乙烯信号通路基因均呈现上调趋势，表明H₂O₂可增强PmA材料中茉莉酸（JA）/乙烯（Et）通路的功能。为进一步探究这些基因是否参与小麦白粉病响应，本研究对感染小麦白粉病菌（Blumeria graminis f. sp. tritici, Bgt）的小麦幼苗，开展了19个H₂O₂响应的推定防御相关基因的表达检测。结果显示其中8个基因同时受H₂O₂与Bgt的共同调控，进一步通过病毒诱导基因沉默（virus induced gene silencing, VIGS）验证发现，脂肪酸去饱和酶基因TaFAD是小麦抗白粉病所必需的基因。综上，本研究首次绘制了H₂O₂胁迫下小麦转录组的全局表达图谱，揭示了H₂O₂响应与Bgt响应之间的潜在关联，为小麦抗白粉病育种提供了重要的候选基因资源。