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Abstract
背景回顾：Increasing grain yield is a major goal of breeders due to the rising global demand for food. We previously reported that the miR397–LACCASE (OsLAC) module regulates brassinosteroid (BR) signaling and grain yield in rice (Oryza sativa).
提出问题：However, the precise roles of laccase enzymes in the BR pathway remain unclear.
结果1-LAC-TTL-BR-籽粒产量：Here, we report that OsLAC controls grain yield by preventing the turnover of TRANSTHYRETIN-LIKE (OsTTL), a negative regulator of BR signaling. Overexpressing OsTTL decreased BR sensitivity in rice, while loss-of-function of OsTTL led to enhanced BR signaling and increased grain yield.
结果2-LAC-TTL磷酸化：OsLAC directly binds to OsTTL and regulates its phosphorylation-mediated turnover. The phosphorylation site Ser226 of OsTTL is essential for its ubiquitination and degradation. Overexpressing the dephosphorylation-mimic form of OsTTL (OsTTLS226A) resulted in more severe defects than did overexpressing OsTTL.
结论：These findings provide insight into the role of an ancient laccase in BR signaling and suggest that the OsLAC–OsTTL module could serve as a target for improving grain yield.
摘 要
由于全球对于粮食的需求不断增加，粮食产量的提高成为育种者的一个主要目标。作者之前报道过miR397-OsLAC模块调控水稻的油菜素内酯（BR）信号转导及籽粒产量。但是，漆酶在BR通路中的确切作用尚不清楚。本文中，作者进一步报道了OsLAC通过阻止BR信号转导负调控子OsTTL蛋白的周转/更新（turnover）来控制粮食产量。过表达OsTTL降低了水稻的BR敏感性，而OsTTL功能缺失则会导致BR信号转导增强以及籽粒产量的增加。OsLAC能够直接结合OsTTL并调节其磷酸化介导的周转。OsTTL蛋白在Ser226位点的磷酸化对其泛素化和降解至关重要。过表达OsTTL的去磷酸化模拟变体OsTTLS226A会导致比过表达OsTTL更为严重的缺陷。本文的发现为古老的漆酶在BR信号转导中的作用提供了新的视野，并表明OsLAC-OsTTL模块可以在未来用作提高粮食产量的一个分子靶标。
中山大学陈月琴教授和练剑平副教授为本文共同通讯作者，广东农科院于洋副研究员为本文第一作者。该研究得到了国家自然科学基金（U1901202和32200441）、“十四五”广东省农业科技创新十大主攻方向（2022SDZG05）、广东省基础与应用基础研究基金（2022A1515010858）以及广东省农作物种质资源保存与利用重点实验室开放课题（ZZZY2001）的联合资助。
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