中文摘要：

[目的]家蚕Bombyx mori微粒子病是蚕业生产上的毁灭性病害,家蚕微孢子虫Nosema bombycis是该病的病原,可经卵垂直传播和经口水平传播。为了探索家蚕微孢子虫中对重复元件的抵御以及对基因转录调控的潜在方式,本研究拟在基因组水平上对该物种的小RNAs进行全面系统的分析,鉴定与转座子相关的小RNAs和潜在的miRNAs。[方法]从感染家蚕微孢子虫的家蚕中肠中提取总RNA,分离小片段RNA并反转录后,进行Solexa高通量测序。通过生物信息学方法对小RNAs进行分类及功能注释,鉴定起源于家蚕微孢子虫不同类型转座子的小RNAs,并对潜在的miRNA进行预测分析。[结果]家蚕微孢子虫小RNAs的长度主要是24和25 nt,其中大部分序列表现出5＇末端的尿嘧啶偏好性。家蚕微孢子虫中存在丰富的与转座子相关联的小RNAs,并且与转座子标准序列匹配的反义小RNAs明显多于正义小RNAs。同时,鉴定获得了31个候选miRNAs,部分为Nosema属的其他孢子虫中所共有,暗示其在微孢子虫基因组进化上具有保守性。[结论]首次鉴定到家蚕微孢子虫的转座子相关性小RNAs,暗示小RNAs在家蚕微孢子虫基因组对转座子防御过程中起到作用,31个潜在的miRNAs为家蚕微孢子虫miRNAs的功能验证提供了后续靶标。

英文摘要：

[Aim]The microsporidian Nosema bombycis can produce epizootic outbreaks in populations of the domestic silkworm（ Bombyx mori） by the major mode of vertical transmission and horizontal transmission. In order to explore the genomic defense system against repetitive elements and potential means of gene regulation in N. bombycis,we conducted the survey of small RNAs associated with transposons and identification of the potential miRNAs in this silkworm parasite. [Methods ] Total RNAs were extracted from silkworm midguts infected by N. bombycis spores and small RNA cD NA libraries were constructed for deep sequencing. After Solexa sequencing,we performed the functional characterization of N. bombycis small RNAs based on the reference genomic sequence through bioinformatics. [Results]N. bombycis has predominantly small RNAs with the length of 24 and 25 nt,most of which show a strong base bias for U at the 5＇ end. Redundant small RNAs were associated with transposons in N. bombycis,and the amount of antisense small RNAs aligned with transposons was much more than that of sense small RNAs. Thirty-one candidate miRNAs were characterized by means of computational prediction,and certain miRNAs were shared by other Nosema species,suggesting that they may evolve conservatively. [Conclusion]There should exist small RNAs genomic defense system against transposons in N. bombycis. Tentative identification of potential thirty-one miRNAs provides a basis for further functional research of their targets.