植物microRNA的保守性及其分布的分析

MicroRNA(miRNA)是真核生物中具有重要调控作用的小分子非编码RNA。本文对miRNA官网miRBase数据库Release 22.1中隶属于植物界的绿藻门、苔藓植物门、蕨类植物门、裸子植物门、被子植物门共计82个物种的miRNA进行了统计分析。miRBase共收录植物miRNA 前体8 615个，成熟miRNA 10 414条，隶属于2 892个miRNA家族。绿藻门miRNA与其他4个门miRNA无同源性；对其他4个门植物miRNA的保守性进行研究，发现存在于2个植物门的miRNA家族有26个，属于中度保守miRNA家族；14个miRNA家族存在于3个及3个以上植物门中，属于高度保守miRNA家族，其中7个miRNA家族系苔藓、蕨类、裸子和被子植物共有，是植物中最保守的miRNA。分析表明，超过30个miRNA家族的植物有35种。进一步对40个中度或者高度保守miRNA在35种植物中的分布进行研究，发现miRNA家族及其成员在物种间的分布存在较大的差异。这些分布上的差异一方面反映不同植物中miRNA的研究深度不同，另一方面也反映出miRNA在植物进化过程中的适应性调整。研究不同植物中miRNA家族的分布，可在miRNA水平为植物早期进化同源性的研究提供分子依据。

Conservation and Distribution of MicroRNA in Plants

MicroRNA is a kind of small molecule non-coding RNA that plays important regulatory roles in eukaryotes. We statistically analyzed the plant miRNAs deposited in miRBase (Release 22.1) which include 82 plant species belong to Chlorophyta, Bryophyta, Pteridophyta, Gymnospermae and Magnoliophyta. Totally, there are 8 615 plant miRNA precursors and 10 414 mature miRNAs belonging to 2 892 miRNA families deposited in miRBase. The Chlorophyta miRNA has no homology with the other four phyla miRNAs. Therefore, we focused on the conservation of miRNAs in the other four phyla. There are 26 miRNA families existing in two plant phyla. They are designed as moderately conserved miRNA family; there are 14 miRNA families existing in at least three plant phyla and belonging to the highly conserved miRNA family; among them, seven miRNA families are found in Bryophyta, Pteridophyta, Gymnospermae and Magnoliophyta. They are the most conserved miRNAs among plant species. The analysis showed that there are 35 plant species owing more than 30 miRNA families. The distribution of the 40 moderately or highly conserved miRNA families were analyzed in these 35 plant species, and found that the distribution of miRNA families and miRNA numbers in the same family are quite different among different species. These differences may derive from the varied depths that miRNAs were studied in different plant species, in another way, they reflect that plants had adjusted their miRNA component and members for adapting to the environment in the process of plant evolution. Studying the distribution of miRNA families in different plants can provide molecular basis for studies on early evolutionary homology of plants at the miRNA level.