梨火疫病菌两个Sec依赖的外泌纤维素酶鉴定及在侵染梨幼果过程中的基因表达分析

Identification of Two Sec-dependent Cellulases in Erwinia amylovora and Gene Expression Analysis During Infection of Immature Pear Fruit

利用生物信息学技术结合基于大肠杆菌的碱性磷酸酯酶(PhoA)检测体系,在梨火疫病菌(Erwinia amylovora)全基因组序列中筛选鉴定了2个依赖Sec途径分泌的纤维素酶:内切葡聚糖酶EAMY3602和β-葡萄糖苷酶EAMY1236。将梨火疫病菌DSM17948接种酥梨幼果,分别于接种后0、8和24 h定量检测基因表达,结果显示EAMY3602编码基因(Ea3602)在接种后8和24 h的mRNA表达量逐渐降低,但与0 h相比无显著差异;EAMY1236编码基因(Ea1236)在接种后8和24 h的mRNA表达量逐步提高,较0 h分别提高了2.43和3.26倍,差异具有统计学意义(P<0.01)。由研究结果推测Sec依赖分泌的内切葡聚糖酶EAMY3602可能与梨火疫病菌侵染无关,而β-葡萄糖苷酶EAMY1236可能是梨火疫病菌的毒力因子,在侵染寄主植物过程中发挥作用。

In this study, by using bioinformatics analysis and Escherichia coli-based alkaline phosphatase(PhoA) gene fusion system, we identified two Sec-dependent secreted cellulases, an endoglucanase EAMY3602 and a β-glucosidase EAMY1236, from the whole genome of Erwinia amylovora. The cell suspension of E. amylovora strain DSM17948 was inoculated into the young pear fruits, quantitative detection of gene expression at 0, 8 and 24 hpi(hours post-inoculation), respectively, which showed that the mRNA expression levels of Ea3602, the coding gene of EAMY3602, were continuously decreased at 8 and 24 hpi, with no significant difference when compared with that at 0 hpi. The transcript levels of Ea1236, the coding gene of EAMY1236, at 8 and 24 hpi were 2.43 and 3.26 fold higher than that at 0 hpi. Research results showed that the Sec-dependent secreted endoglucanase EAMY3602 had no implication in plant infection, but β-glucosidase EAMY1236 probably acted as a virulence factor that plays role in the process of E. amylovora infecting the immature pears.