State Key Laboratory of Genetic Engineering, Collaborative Innovation Center for Genetics and Development, Institute of Plant Biology, School of Life Sciences, Fudan University, Shanghai, 200438, China.
Sci China Life Sci. 2015 Mar;58(3):246-52. doi: 10.1007/s11427-015-4800-0. Epub 2015 Jan 29.
In plants, each pollen mother cell undergoes two rounds of cell divisions to form a mature pollen grain, which contains a vegetative cell (VC) and two sperm cells (SC). As a companion cell, the VC carries the SCs to an ovule by germinating a pollen tube. In-depth sequencing analyses of mature pollen showed that microRNAs (miRNAs) and short interfering RNAs (siRNAs) are present in both the VC and SCs. Additionally, epigenetically-regulated transposable elements (TEs) are reactivated in the VC and these TE mRNAs are further processed into 21-nt epigenetically reactivated siRNA (easiRNA) in SCs, which prevent 24-nt siRNA accumulation and sequester miRNA loading. Small RNAs are thought to move from the VC to SCs, where they regulate gene expression and reinforce TE silencing. Here, we summarize current knowledge of the biogenesis and function of miRNAs, siRNAs, and easiRNAs in pollen, emphasizing how these different small RNAs coordinately contribute to sperm cell formation and TE silencing.
在植物中，每个花粉母细胞经历两轮细胞分裂，形成一个成熟的花粉粒，其中包含一个营养细胞 (VC) 和两个精子细胞 (SC)。作为一个伴细胞，VC 通过萌发花粉管将 SC 带到一个胚珠中。对成熟花粉的深度测序分析表明，miRNAs（miRNA）和小干扰 RNA（siRNA）存在于 VC 和 SC 中。此外，在 VC 中，受表观遗传调控的转座元件 (TE) 被重新激活，这些 TE mRNA 进一步在 SC 中加工成 21-nt 表观遗传再激活 siRNA（easiRNA），从而防止 24-nt siRNA 的积累和 miRNA 的装载。小 RNA 被认为从 VC 移动到 SC，在那里它们调节基因表达并加强 TE 的沉默。在这里，我们总结了 miRNA、siRNA 和 easiRNA 在花粉中的生物发生和功能的现有知识，强调了这些不同的小 RNA 如何协调促进精子细胞的形成和 TE 的沉默。
