Collaborative Innovation Center of Henan Grain Crops, Henan Agricultural University, Zhengzhou 450046, China; Key Laboratory of Rice Biology in Henan Province, Henan Agricultural University, Zhengzhou 450046, China; Henan Engineering Laboratory of Rice, Henan Agricultural University, Zhengzhou 450002, China.
Joint Center for Single Cell Biology/School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai 200240, China.
Plant Commun. 2023 Sep 11;4(5):100604. doi: 10.1016/j.xplc.2023.100604. Epub 2023 Apr 20.
Grain weight and quality are always determined by grain filling. Plant microRNAs have drawn attention as key targets for regulation of grain size and yield. However, the mechanisms that underlie grain size regulation remain largely unclear because of the complex networks that control this trait. Our earlier studies demonstrated that suppressed expression of miR167 (STTM/MIM167) substantially increased grain weight. In a field test, the yield increased up to 12.90%-21.94% because of a significantly enhanced grain filling rate. Here, biochemical and genetic analyses revealed the regulatory effects of miR159 on miR167 expression. Further analysis indicated that OsARF12 is the major mediator by which miR167 regulates rice grain filling. Overexpression of OsARF12 produced grain weight and grain filling phenotypes resembling those of STTM/MIM167 plants. Upon in-depth analysis, we found that OsARF12 activates OsCDKF;2 expression by directly binding to the TGTCGG motif in its promoter region. Flow cytometry analysis of young panicles from OsARF12-overexpressing plants and examination of cell number in cdkf;2 mutants verified that OsARF12 positively regulates grain filling and grain size by targeting OsCDKF;2. Moreover, RNA sequencing results suggested that the miR167-OsARF12 module is involved in the cell development process and hormone pathways. OsARF12-overexpressing plants and cdkf;2 mutants exhibited enhanced and reduced sensitivity to exogenous auxin and brassinosteroid (BR) treatment, confirming that targeting of OsCDKF;2 by OsARF12 mediates auxin and BR signaling. Our results reveal that the miR167-OsARF12 module works downstream of miR159 to regulate rice grain filling and grain size via OsCDKF;2 by controlling cell division and mediating auxin and BR signals.
粒重和品质始终由籽粒灌浆决定。植物 microRNAs 作为调控粒型和产量的关键靶标引起了关注。然而，由于控制该性状的复杂网络，粒型调控的机制在很大程度上仍不清楚。我们之前的研究表明，miR167（STTM/MIM167）的表达受到抑制可显著增加粒重。在田间试验中，由于灌浆速率显著提高，产量增加了 12.90%-21.94%。在这里，生化和遗传分析揭示了 miR159 对 miR167 表达的调控作用。进一步的分析表明，OsARF12 是 miR167 调控水稻灌浆的主要介质。过表达 OsARF12 产生了类似于 STTM/MIM167 植株的粒重和灌浆表型。经过深入分析，我们发现 OsARF12 通过直接结合其启动子区域的 TGTCGG 基序激活 OsCDKF;2 的表达。过表达 OsARF12 的水稻幼穗的流式细胞术分析和 cdkf;2 突变体中细胞数量的检测证实，OsARF12 通过靶向 OsCDKF;2 正向调控灌浆和粒重。此外，RNA 测序结果表明，miR167-OsARF12 模块参与细胞发育过程和激素途径。过表达 OsARF12 的植株和 cdkf;2 突变体对外源生长素和油菜素内酯（BR）处理的敏感性增强和降低，证实 OsARF12 对 OsCDKF;2 的靶向作用通过调节生长素和 BR 信号转导。我们的研究结果表明，miR167-OsARF12 模块通过 OsCDKF;2 作用于下游，通过控制细胞分裂和调节生长素和 BR 信号转导，调控水稻灌浆和粒重。
