[Objective] The poplar'Robusta',susceptible to virulent rust E4 Melampsora larici-populina,provides suitable host material for the study of the plant host resistance/susceptibility to pathogen.Previously study indicates that the transcription factor (TF) plays an important role in determining the poplar susceptibility.In this study,the authors tried to determine the R2R3-MYB TF genes driving basal disease resistance and focus on microRNAs (miRNAs) regulation.[Method] Two small RNA (sRNA) libraries,a degradome cDNA library and 2 digital gene expression libraries were constructed for rust-inoculated (Rust +) and rust-free (Rust-) susceptible poplar'Robusta'leaves through high-throughput sequencing.The expression of selected miRNA and target R2R3-MYBs were identified by RTq-PCR.[Result]Altogether,230 R2R3-MYBs were identified.Among those R2R3-MYBs,the expression of 55 genes were suppressed/promoted following the drive straight of the rust,the others were unchanged.Based on the miRNA and degradome sequencing,86 regulating interactions (22 miRNA to 18 R2R3-MYB) were identified.RTq-PCR of selected PC-3p-2521022_1 and PndMYB173 showed a negative post-transcriptional regulation.The R2R3-MYBs target genes predication indicated R2R3-MYBs related to many resistance and phytohormone pathways,such as response to salicylic acid stimulus,response to stress,response to jasmonic acid stimulus and response to abscisic acid stimulus.[Conclusion] The infection of virulent rust changed the expression of 23.9％ R2R3-MYBs.The differential expression of R2R3-MYBs indicated that the rust fungi infection could not only switch on but also switch off R2R3-MYB TF genes.Under the stress of rust infection,the post-transcriptional regulation of R2R3-MYBs was regulated by the families of miR159 and miR858.%[目的]强致病锈菌亲和型树种欧美杨适合做寄主感病分子机理研究.研究表明转录因子及其调控miRNA在杨树抗/感病过程中起重要的信号传导和调控作用,决定杨树与锈菌的亲和性.为深入研究杨树感病性,对欧美杨R2 R3-MYB转录因子及其调控miRNA进行研究.[方法]构建锈菌侵染和未侵染miRNA组、降解组文库和基因表达谱文库,进行高通量测序.对基因表达谱结果进行生物信息学分析鉴定R2R3-MYBs,根据miRNA组和降解组数据确定R2R3-MYBs调控miRNA.应用定量PCR技术鉴定候选R2R3-MYBs和其调控miRNA的表达量.[结果]共鉴定到230个欧美杨R2R3-MYBs,其中55个R2 R3-MYBs在锈菌侵染和未侵染叶片间表达量差异显著,其余表达量变化不显著.基于降解组,共鉴定到由22个miRNA调控18个R2R3-MYBs的86个转录后调控关系.定量PCR结果表明PC-3 p-2521022_1与PndMYB173存在转录后负调控关系.预测的R2R3-MYB靶基因涉及水杨酸、茉莉酸、乙烯和脱落酸等多个植物激素抗性路径.[结论]E4强致病锈菌侵染导致亲和型树种欧美杨23.9％的R2 R3-MYBs表达量发生变化,锈菌侵染不但可以影响R2R3-MYBs的表达量,还可以启动或关闭R2R3-MYBs的表达.欧美杨在F4强致病锈菌胁迫条件下,R2R3-MYBs转录后主要受miR159和miR858家族的miRNA调控.
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