黄瓜基因组中抗霜霉病候选基因的生物信息学及其表达特异性

【目的】寻找黄瓜抗霜霉病基因，研究黄瓜抗霜霉病机制。【方法】利用拟南芥和甜瓜抗霜霉病蛋白质序列，搜索黄瓜基因组数据库；通过生物信息学分析候选基因特征，以黄瓜抗霜霉病自交系M801-3-1为试材，分析候选基因在叶片组织中的表达状态。【结果】共获得187个黄瓜抗霜霉病候选基因；确定了候选基因染色体位置和排列特点、序列相似性特征以及系统进化关系；大部分黄瓜R基因在未接种霜霉病菌的抗病自交系和感病叶片组织中都有一定的表达量，在接种霜霉病菌后在抗病自交系M801-3-1中Csa001907和Csa002921表达量下调，感病自交系M302-3 中Csa001907和Csa002921变化不明显。【结论】在黄瓜基因组中存在185个与拟南芥抗霜霉病基因同源的R基因，2个与甜瓜的抗霜霉病基因At1和At2同源的eR基因，通过聚类分析这些基因可以分为6类，初步认定Csa001907和Csa002921为黄瓜抗霜霉病的R基因，这2个基因在叶片组织中有一定表达量，其表达量减少可诱发抗病黄瓜品种的抗病反应。

Bioinformatics of Downy Mildew Resistance to Cucumber Candidate Genes and Specific Expression in Organise

【Objective】The objective of this study is to investigate the downy mildew resistance genes in cucumber, and to clarify its molecular mechanism. 【Method】Cucumber candidate genes with resistance against downy mildew were identified from the cucumber genome database and blast protein sequences in Arabidopsis thaliana, and melon downy mildew resistance genes. Cucumber candidate genes were analyzed by bioinformatics way. Inbred line M801-3-1 with downy mildew resistance was used as test materials. Expression patterns of the genes were monitored by RT-PCR technique in cucumber leaf.【Result】One hundred and eighty-seven cucumber candidate genes as resistances against downy mildew were identified. Through bioinformatics analysis, the location of candidate genes in chromosomes and characteristics of arrangement were confirmed, and sequence comparability characteristics and relationship of system evolution were analyzed. The results of RT-PCR test indicated that most of the tested genes expressed either sprayed with the pathogen or water. The results of Florescent real-time quantitative RT-PCR test indicated that only Csa001907 and Csa002921 showed significant reduction in the leaves sprayed with the pathogen. 【Conclusion】 In the cucumber genome, there are 185 genes homologous A. thaliana downy mildew resistance genes, and there are 2 genes homologous melon resistance to downy mildew genes At1 and At2. Through clustering analysis these genes can be divided into 6 categories. Csa001907 and Csa002921 are most likely R gene of cucumber downy mildew resistance. R genes may be stablly expressed in leaves, R genes original expressions are interfered that may be the reasons of cucumber downy mildew infections.