PhasiRNAs (phased, small interfering RNAs) play a crucial role in supporting male fertility in grasses. Earlier work in maize (Zea mays) and rice (Oryza sativa) – and subsequently many other plant species – identified premeiotic 21-nt and meiotic 24-nt phasiRNAs. More recently, a group of premeiotic 24-nt phasiRNAs was discovered in the anthers of two Pooideae species, barley (Hordeum vulgare) and bread wheat (Triticum aestivum). Whether premeiotic 24-nt phasiRNAs and other classes of reproductive phasiRNAs are conserved across Pooideae species remains unclear. We conducted comparative RNA profiling of three anther stages in six Pooideae species and one Bambusoideae species. We observed complex temporal accumulation patterns of 21-nt and 24-nt phasiRNAs in Pooideae and Bambusoideae grasses. In Bambusoideae, 21-nt phasiRNAs accumulated during meiosis, whereas 24-nt phasiRNAs were present in both premeiotic and postmeiotic stages. We identified premeiotic 24-nt phasiRNAs in all seven species examined. These phasiRNAs exhibit distinct biogenesis mechanisms and potential Argonaute effectors compared to meiotic 24-nt phasiRNAs. We show that specific Argonaute genes co-expressed with stage-specific phasiRNAs are conserved across Bambusoideae and Pooideae species. Our degradome analysis identified a set of conserved miRNA target genes across species, while 21-nt phasiRNA targets were species-specific. Cleavage of few targets was observed for 24-nt phasiRNAs. In summary, this study demonstrates that premeiotic 24-nt phasiRNAs are present across Bambusoideae and Pooideae families, and the temporal accumulation of other classes of 21-nt and 24-nt phasiRNA differs between bamboo and Pooideae species. Furthermore, targets of the three classes of phasiRNAs may be rapidly evolving or undetectable.

中文翻译：

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比较 RNA 分析可识别 Bambusoideae 和 Pooideae 物种中的阶段特异性 phasiRNA 和共表达的 Argonaute 基因


PhasiRNA（相位小干扰 RNA）在支持禾本科植物的雄性生育能力方面起着至关重要的作用。玉米 （Zea mays） 和水稻 （Oryza sativa） 的早期工作 - 以及随后的许多其他植物物种 - 确定了减数分裂前 21-nt 和减数分裂 24-nt phasiRNA。最近，在两种 Pooideae 物种大麦 （Hordeum vulgare） 和面包小麦 （Triticum aestivum） 的花药中发现了一组减数分裂前的 24-nt phasiRNA。减数分裂前 24-nt phasiRNAs 和其他类别的生殖 phasiRNAs 在 Pooideae 物种中是否保守尚不清楚。我们对 6 种 Pooideae 和 1 种 Bambusoideae 的三个花药阶段进行了比较 RNA 分析。我们在 Pooideae 和 Bambusoideae 草中观察到 21-nt 和 24-nt phasiRNAs 的复杂时间积累模式。在 Bambusoideae 中，21-nt phasiRNAs 在减数分裂期间积累，而 24-nt phasiRNAs 存在于减数分裂前和减数分裂后阶段。我们在检查的所有 7 个物种中鉴定了减数分裂前的 24-nt phasiRNA。与减数分裂 24-nt phasiRNA 相比，这些 phasiRNA 表现出不同的生物发生机制和潜在的 Argonaute 效应子。我们表明，与阶段特异性 phasiRNA 共表达的特异性 Argonaute 基因在 Bambusoideae 和 Pooideae 物种中是保守的。我们的降解组分析确定了一组跨物种的保守 miRNA 靶基因，而 21-nt phasiRNA 靶标是物种特异性的。观察到 24-nt phasiRNAs 的少数靶标切割。总之，本研究表明，减数分裂前的 24-nt phasiRNAs 存在于 Bambusoideae 和 Pooideae 家族中，其他类别的 21-nt 和 24-nt phasiRNA 的时间积累在竹子和 Pooideae 物种之间有所不同。 此外，这三类 phasiRNA 的靶标可能正在快速进化或无法检测到。