Regulation of seed size is a key strategy for improving crop yield and is also a basic biological question. However, the molecular mechanisms by which plants determine their seed size remain elusive. Here, we report that the GW2-WG1-OsbZIP47 regulatory module controls grain width and weight in rice. WG1, which encodes a glutaredoxin protein, promotes grain growth by increasing cell proliferation. Interestingly, WG1 interacts with the transcription factor OsbZIP47 and represses its transcriptional activity by associating with the transcriptional co-repressor ASP1, indicating that WG1 may act as an adaptor protein to recruit the transcriptional co-repressor. In contrary, OsbZIP47 restricts grain growth by decreasing cell proliferation. Further studies reveal that the E3 ubiquitin ligase GW2 ubiquitinates WG1 and targets it for degradation. Genetic analyses confirm that GW2, WG1, and OsbZIP47 function in a common pathway to control grain growth. Taken together, our findings reveal a genetic and molecular framework for the control of grain size and weight by the GW2-WG1-OsbZIP47 regulatory module, providing new targets for improving seed size and weight in crops.
水稻是世界上最重要的糧食作物之一，提高水稻產量對全球人口的快速增長至關重要。種子大小和重量是重要的產量性狀，因此最佳化種子大小和重量是提高農作物產量的關鍵策略。
本研究從水稻過表達突變體庫中分離了一個種子變寬變重的轉基因系WG1-OE。WG1編碼一個CC類型谷氧還蛋白OsGRX8，該主要蛋白定位于細胞核中。過量表達該基因可顯著增加粒寬和粒重，利用CRISPR/Cas9技術敲除WG1導致籽粒變窄變長。細胞學分析表明WG1通過促進細胞分裂調控粒寬。WG1與轉錄因子OsbZIP47直接互作，招募轉錄共抑制子ASP1來抑制OsbZIP47的轉錄活性，從而調控下游基因的表達。
過表達OsbZIP47轉基因植株籽粒窄長，而osbzip47突變體籽粒變寬。進一步研究發(fā)現E3泛素連接酶GW2可以泛素化WG1，并調控WG1的蛋白穩(wěn)定性。遺傳分析表明GW2、WG1和 bZIP47作用在同一遺傳途徑調控籽粒大小和重量。該研究揭示了GW2-WG1-OsbZIP47途徑調控水稻籽粒大小的新機制，為作物高產育種提供了重要的基因資源。