• RNA-dependent RNA polymerases (RDR) generate double-stranded (ds)RNA triggers for RNA silencing across eukaryotes. Among the three clades, α-clade and β-clade members are key components of RNA silencing and mediators of stress responses across eukaryotes. However, γ-clade members are unusual in that they are represented in phylogenetically distant plants and fungi, and their functions are unknown.
• Using genetic, bioinformatic and biochemical methods, we show that γ-clade RDRs from Oryza sativa L. are involved in plant development as well as regulation of expression of coding and noncoding RNAs.
• Overexpression of γ-clade RDRs in transgenic rice and tobacco plants resulted in robust growth phenotype, whereas their silencing in rice displayed strong inhibition of growth. Small (s)RNA and RNA-seq analysis of OsRDR3 mis-expression lines suggested that it is specifically involved in the regulation of repeat-rich regions in the genome. Biochemical analysis confirmed that OsRDR3 has robust polymerase activities on both single stranded (ss)RNA and ssDNA templates similar to the activities reported for α-clade RDRs such as AtRDR6.
• Our results provide the first evidence of the importance of γ-clade RDRs in plant development, their atypical biochemical activities and their contribution to the regulation of gene expression.

中文翻译：

---

γ-进化枝 RNA 依赖性 RNA 聚合酶在水稻发育和产量相关性状中的重要作用与其调节特定基因组区域的非典型聚合酶活性有关

• RNA 依赖性 RNA 聚合酶 (RDR) 生成双链 (ds) RNA 触发器，用于跨真核生物的 RNA 沉默。在这三个进化枝中，α-进化枝和 β-进化枝成员是 RNA 沉默的关键组成部分，也是真核生物应激反应的介质。然而，γ-进化枝成员的不寻常之处在于它们存在于系统发育上较远的植物和真菌中，并且它们的功能是未知的。
• 使用遗传、生物信息学和生化方法，我们表明来自Oryza sativa L. 的 γ-进化枝 RDR 参与植物发育以及编码和非编码 RNA 表达的调节。
• γ-进化枝 RDRs 在转基因水稻和烟草植物中的过表达导致强劲的生长表型，而它们在水稻中的沉默显示出强烈的生长抑制。OsRDR3 错误表达系的小 (s)RNA 和 RNA-seq 分析表明它专门参与基因组中重复丰富区域的调节。生化分析证实，OsRDR3 在单链 (ss)RNA 和 ssDNA 模板上都具有强大的聚合酶活性，类似于针对 α-进化枝 RDR（如 AtRDR6）所报道的活性。
• 我们的研究结果首次证明了 γ-进化枝 RDR 在植物发育中的重要性、它们的非典型生化活性以及它们对基因表达调控的贡献。