RNA-dependent RNA polymerase 6 (RDR6) is a core component of the small RNA biogenesis pathway, but its function in meiosis is unclear. Here, we report a new allele of OsRDR6 (Osrdr6-meiosis [Osrdr6-mei]), which causes meiosis-specific phenotypes in rice (Oryza sativa). In Osrdr6-mei, meiotic double-strand break (DSB) formation is partially blocked. We created a biallelic mutant with more severe phenotypes, Osrdr6-bi, by crossing Osrdr6-mei with a knockout mutant, Osrdr6-edit. In Osrdr6-bi meiocytes, 24 univalents were observed, and no histone H2AX phosphorylation foci were detected. Compared with the wild type, the number of 21-nucleotide small RNAs in Osrdr6-mei was dramatically lower, while the number of 24-nucleotide small RNAs was significantly higher. Thousands of differentially methylated regions (DMRs) were discovered in Osrdr6-mei, implying that OsRDR6 plays an important role in DNA methylation. There were 457 genes downregulated in Osrdr6-mei, including three genes, CENTRAL REGION COMPONENT1, P31^comet, and O. sativa SOLO DANCERS, related to DSB formation. Interestingly, the downregulated genes were associated with a high level of 24-nucleotide small RNAs but less strongly associated with DMRs. Therefore, we speculate that the alteration in expression of small RNAs in Osrdr6 mutants leads to the defects in DSB formation during meiosis, which might not be directly dependent on RNA-directed DNA methylation.

RNA依赖性RNA聚合酶6（RDR6）是小RNA生物发生途径的核心组成部分，但其在减数分裂中的功能尚不清楚。在这里，我们报告了Osrdr6的一个新等位基因（ Osrdr6-减数分裂[ Osrdr6-mei ]），它导致水稻（ Oryza sativa ）减数分裂特异性表型。在Osrdr6-mei中，减数分裂双链断裂 (DSB) 的形成被部分阻断。我们通过将Osrdr6-mei与敲除突变体Osrdr6-edit杂交，创建了具有更严重表型的双等位突变体Osrdr6-bi 。在Osrdr6-bi 性母细胞中，观察到 24 个单价体，并且未检测到组蛋白 H2AX 磷酸化灶。与野生型相比， Osrdr6-mei中21核苷酸小RNA的数量明显减少，而24核苷酸小RNA的数量明显增多。 Osrdr6-mei中发现了数千个差异甲基化区域（DMR），这表明 OsRDR6 在 DNA 甲基化中发挥着重要作用。 Osrdr6-mei中有457个基因下调，其中与DSB形成相关的CENTRAL REGION COMPONENT1 、 P31 ^comet和O. sativa SOLO DANCERS 3个基因。有趣的是，下调的基因与高水平的 24 核苷酸小 RNA 相关，但与 DMR 的相关性不太强。因此，我们推测Osrdr6突变体中小RNA表达的改变导致了减数分裂过程中DSB形成的缺陷，这可能不直接依赖于RNA指导的DNA甲基化。