miRNA是真核生物中广泛存在的一类小分子非编码RNA，主要参与转录后基因表达调控，在动植物正常生长发育和环境应答中起重要调节作用。关于植物miRNA加工成熟的生化途径已经明晰，但对其调控机制的研究方兴未艾。双链RNA结合蛋白HYL1是加工酶DCL1的核心伴侣，研究表明HYL1有助于提高DCL1的加工效率和准确性，但具体作用机制以及HYL1是否存在其他生物学功能仍不清楚。项目前期通过遗传学筛选发现核内外切酶体成员SOP1和HEN2的突变可以显著回复hyl1-2突变体的发育缺陷及部分miRNA的表达水平，提示核内外切酶体负向调控miRNA的加工生成。本项目拟进一步探讨哪些核内RNA降解途径参与miRNA生成及其遗传互作关系，并重点围绕SOP1和HEN2的底物识别，以及HYL1如何拮抗外切酶体调控miRNA生成的分子机制开展研究。研究成果将拓展我们对miRNA加工成熟过程中质量控制机制的认识。

miRNAs are a class of eukaryotic small non-coding RNAs involved in the post-transcriptional regulation of gene expression, and play crucial roles in modulating normal development and environmental responses in animals and plants. Although the biochemical pathway of miRNA biogenesis pathway in plants has been well established, not much is known about its regulation. HYL1 encodes a double-stranded RNA binding protein that functions as a core chaperone of the miRNA processing enzyme DCL1. Current studies have shown that HYL1 improves both the processing efficiency and accuracy of DCL1, but its mechanism of action and whether HYL1 has other biological functions remain elusive. Through genetic screening, we found that mutations in two nucleus exosome components, SOP1 and HEN2, can largely restore the developmental defects of the hyl1-2 mutant and the expression levels of some miRNAs, suggesting that the nucleus exosome negatively regulates the biogenesis of miRNA. In this project, we will further explore whether additional nuclear RNA degradation pathways are involved in miRNA biogenesis and their genetic interactions. We will focus on the molecular mechanism of SOP1 and HEN2 in substrate recognition, and how HYL1 antagonizes exosome activity to ensure proper miRNA production. This research will expand our understanding of the quality control mechanisms during miRNA processing and maturation.