PhasiRNAs (phased secondary siRNAs) play important regulatory roles in the development processes and biotic or abiotic stresses in plants. Some of phasiRNAs involve in the reproductive development in grasses, which include two categories, 21-nt (nucleotide) and 24-nt phasiRNAs. They are triggered by miR2118 and miR2275 respectively, in premeiotic and meiotic anthers of rice, maize and other grass species. Wheat (Triticum aestivum) with three closely related subgenomes (subA, subB and subD), is a model of allopolyploid in plants. Knowledge about the role of phasiRNAs in the inflorescence development of wheat is absent until now, and the evolution of PHAS loci in polyploid plants is also unavailable. Using 261 small RNA expression datasets from various tissues, a batch of PHAS (phasiRNA precursors) loci were identified in the young spike of wheat, most of which were regulated by miR2118 and miR2275 in their target site regions. Dissection of PHAS and their trigger miRNAs among the diploid (AA and DD), tetraploid (AABB) and hexaploid (AABBDD) genomes of Triticum indicated that distribution of PHAS loci were dominant randomly in local chromosomes, while miR2118 was dominant only in the subB genome. The diversity of PHAS loci in the three subgenomes of wheat and their progenitor genomes (AA, DD and AABB) suggested that they originated or diverged at least before the occurrence of the tetraploid AABB genome. The positive correlation between the PHAS loci or the trigger miRNAs and the ploidy of genome indicated the expansion of genome was the major drive force for the increase of PHAS loci and their trigger miRNAs in Triticum. In addition, the expression profiles of the PHAS transcripts suggested they responded to abiotic stresses such as cold stress in wheat. Altogether, non-coding phasiRNAs are conserved transcriptional regulators that display quick plasticity in Triticum genome. They may be involved in reproductive development and abiotic stress in wheat. It could be referred to molecular research on male reproductive development in Triticum.

中文翻译：

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异六倍体小麦幼穗中PHAS基因座的进化。

PhasiRNA（分阶段的次级siRNA）在植物的发育过程以及生物或非生物胁迫中起重要的调节作用。一些phasiRNA参与了草的生殖发育，其中包括两类：21-nt（核苷酸）和24-nt phasiRNA。它们分别由水稻，玉米和其他草种的减数分裂前药和减数分裂花药中的miR2118和miR2275触发。具有三个密切相关的亚基因组（subA，subB和subD）的小麦（Triticum aestivum）是植物中同素多倍体的模型。到目前为止，尚无关于phasiRNA在小麦花序发育中作用的知识，而且在多倍体植物中也没有PHAS基因座的进化。利用来自各种组织的261个小RNA表达数据集，在小麦幼穗中鉴定出一批PHAS（phasiRNA前体）基因座，其中大多数在其靶位点区域受miR2118和miR2275调控。Triticum的二倍体（AA和DD），四倍体（AABB）和六倍体（AABBDD）基因组中的PHAS及其触发miRNA的解剖表明，PHAS基因座的分布在局部染色体中随机占优势，而miR2118仅在subB基因组中占优势。小麦三个亚基因组及其祖先基因组（AA，DD和AABB）中PHAS基因座的多样性表明，它们至少在四倍体AABB基因组出现之前就起源或分化。PHAS基因座或触发miRNA与基因组的倍数呈正相关，说明基因组的扩增是小麦中PHAS基因座及其触发miRNA增加的主要驱动力。此外，PHAS转录本的表达谱表明，它们对非生物胁迫（如小麦的冷胁迫）有反应。总而言之，非编码phasiRNA是保守的转录调节因子，在Triticum基因组中显示出快速可塑性。它们可能参与小麦的生殖发育和非生物胁迫。可以参考有关小麦的男性生殖发育的分子研究。