Identification of microRNA responsive to pathogen infection in sugarcane

Sugarcane is a very efficient crop to produce ethanol. In recent years, extensive efforts have been made in order to increase sugarcane yields. To reach this goal, molecular biology tools have been used comprehensively, identifying genes, pathways and genetic polymorphisms. However, some important molecular components, like microRNAs, have not been deeply investigated. MicroRNAs are an important class of endogenous small, noncoding RNAs that regulate gene expression at the post-transcription level and play fundamental roles in diverse aspects of animal and plant biology. Plant genomes harbor numerous miRNA genes that regulate many protein-coding genes to influence key processes ranging from development, metabolism, and responses to abiotic and biotic stresses. There is wide range of pests and diseases that affect sugarcane, yet the mechanisms that regulate pathogen interactions with sugarcane have not been thoroughly investigated. To gain knowledge on the physiological responses to pathogens mediated by microRNAs in sugarcane, we screened the transcriptoma of sugarcane plants infected with Acidovorax avenae subsp avenae, the causal agent of red stripe disease in sugarcane, and detected several microRNAs modulated in the presence of the pathogen. Furthermore, we validated with qPCR a number of microRNA expression patterns observed by bioinformatics analysis. In addition, we observed high expression levels of several star microRNAs, in numbers larger than the mature microRNAs in some cases. Interestingly, sof-miR408 was consistently down-regulated in the presence of several pathogens, but not in the presence beneficial microbes. This result indicates that the sugarcane senses pathogenic or beneficial microorganisms differentially and triggers specific epigenetic regulatory mechanisms accordingly Screenning of sRNA transcriptome of sugarcane plants infected with Acidovorax avenae subsp avenae after seven days

甘蔗是生产乙醇的高效作物。近年来，科研人员围绕提升甘蔗产量开展了大量研究工作。为达成这一目标，分子生物学工具已得到全面应用，用于鉴定相关基因、代谢通路及遗传多态性。然而，包括微小RNA（microRNA）在内的部分重要分子组分尚未得到深入研究。微小RNA是一类重要的内源性非编码小RNA，可在转录后水平调控基因表达，在动植物生物学的诸多过程中发挥核心作用。植物基因组中存在大量miRNA基因，通过调控众多蛋白编码基因，影响植物发育、代谢以及对非生物和生物胁迫的应答等关键进程。甘蔗会受到多种病虫害的侵袭，但调控其与病原菌互作的分子机制仍未得到充分阐释。为解析甘蔗中微小RNA介导的病原菌响应生理机制，本研究对感染燕麦食酸菌燕麦亚种（*Acidovorax avenae* subsp *avenae*，该病原菌是甘蔗红条病的致病菌）的甘蔗植株转录组（transcriptome）进行了筛选，鉴定出多个在病原菌侵染条件下发生表达调控的miRNA。此外，本研究通过实时定量PCR（quantitative real-time PCR, qPCR）验证了生物信息学分析所得到的部分miRNA表达模式。同时，研究还发现多个星号微小RNA（star microRNA）的表达量较高，在部分样本中其表达水平甚至高于成熟miRNA。值得注意的是，sof-miR408在多种病原菌侵染条件下均呈现持续下调表达，但在有益微生物处理组中未出现该表达模式。这一结果表明，甘蔗可差异化识别病原菌与有益微生物，并据此触发特异性的表观遗传调控机制。本研究还对感染燕麦食酸菌燕麦亚种7天的甘蔗植株小RNA（small RNA, sRNA）转录组进行了筛选。