马铃薯晚疫病作为马铃薯生产中的头号病害，是引起粮食作物产量损失最严重的一种真菌病害。孢子囊萌发是P. infestans侵染过程中至关重要的阶段。miRNA在动植物中广泛存在，可通过识别靶基因实现转录后的基因调控。本项目研究拟选取P. infestans菌株三个不同发育时期的组织样品- - 未萌发的孢子囊、萌发的孢子囊和菌丝，利用Illumina技术对三个样本进行小RNA测序，通过数据分析预测P. infestans不同发育阶段的milRNA及其作用的靶基因。并通过sRNA杂交实验证实部分milRNA的存在，找到其发夹前体，初步研究milRNA对靶基因作用机制。通过构建样品之间的小RNA差异表达谱，找出在孢子囊萌发过程中特意表达的miRNA及其靶基因，为深入研究P. infestans与植物寄主的相互作用机制奠定基础。

Late blight, caused by Phytophthora infestans (Mont.) de Bary (Oomycota, Stramenopiles) is the most important diseases threatening potato production in many countries, especially in China. This plant pathogen causes billions of lost in potatoes, tomatoes and other members of the Solanaceae worldwide. In the life cycle of P. infestans, sporangia germination is a critical stage in the process of P. infestans infection. The genome of P. infestans, completed sequencing in 2009, was found to be considerably larger (240 Mbp) than that of most other Phytophthora species whose genomes have been sequenced; Phytophthora sojae has a 95 Mbp genome and Phytophthora ramorum had a 65 Mbp genome. It also contained a diverse variety of transposons and many gene families encoding for effector proteins that are involved in causing pathogenicity. However, MicroRNA is rarely researched in this pathogen. MicroRNAs are small non-coding RNAs of approximately 22 nt with important regulatory roles in post-transcriptional regulation of gene expression. Most published documents indicated that miRNAs play important roles in plant development, such as organ separation, leaf development and polarity, lateral root formation, floral organ identity and reproduction, etc. MiRNAs are alsovery important in regulation of animal development, differentiation, carcinogenesis, and immunoreaction. Since the discovery of the first miRNA in C. elegans, miRNAs have been widely found in animals, plants, and algae, but not in P. infestans or Oomycetes. Our preliminary work shows that there is a highly chance that miRNA also exist in P. infestans and functions to their target genes. This project intends to get the small RNA sequencing data by Illumina platform with the three different developmental stages tissues, non-germinated sporangia, germinated sporangia and mycelium. The sequencing data will be used to analyze the potential miRNAs and predict their hairpin precursors and target genes. Small RNA hybridization will be performed to confirm the presence of miRNAs. Differential expression profiling among different tissues will be built through Bioinformatics analysis. We are going to identify the differentially expressed miRNAs in sporangium germination process, test the expression level with qPCR and predict their target genes. The mechanism of miRNA worked with its target genes will also be researched in this project.