Guangdong Provincial Key Laboratory of Protein Function and Regulation in Agricultural Organisms, College of Life Sciences, South China Agricultural University, Guangzhou 510642, China.
Guangdong Provincial Key Laboratory of Protein Function and Regulation in Agricultural Organisms, College of Life Sciences, South China Agricultural University, Guangzhou 510642, China.
Plant Sci. 2024 Dec;349:112272. doi: 10.1016/j.plantsci.2024.112272. Epub 2024 Sep 24.
Seed size is one of the three main characteristics determining rice yield. Clarification of the mechanisms regulating seed size in rice has implications for improving rice yield. Although several genes have been reported to regulate seed size, most of the reports are fragmentary. The role of metallothioneins (MTs) in regulating seed size remains unknown. Here, we found that OsMT2b was expressed in both spikelets and developing seeds. OsMT2b-overexpression lines had large and heavy seeds, and RNAi (RNA interference) lines had small and light seeds. Scanning electron microscopy (SEM) observations revealed that OsMT2b regulated spikelet hull size by affecting cell expansion in the outer epidermis. Histological analysis indicated that OsMT2b affected the number of cells in the cross-section of spikelet hulls, which affected seed size. The fresh weight of seeds was consistently higher in OsMT2b-overexpression lines than in seeds of the wild-type (WT) and RNAi lines from 6 DAP (days after pollination) until maturity, indicating that OsMT2b affected seed filling. Reverse transcription-quantitative PCR (RT-qPCR) analyses revealed that OsMT2b regulates the expression of reactive oxygen species scavenging-related genes involved in seed size regulation. In conclusion, our results indicated that OsMT2b positively regulates seed size, which provides a novel approach for regulating seed size with genetic engineering technology.
种子大小是决定水稻产量的三个主要特征之一。阐明调控水稻种子大小的机制对提高水稻产量具有重要意义。尽管已经报道了几个基因调控种子大小，但大多数报道都是零散的。金属硫蛋白（MTs）在调控种子大小中的作用仍不清楚。在这里，我们发现 OsMT2b 在小穗和发育中的种子中均有表达。OsMT2b 过表达系的种子较大且较重，而 RNAi（RNA 干扰）系的种子较小且较轻。扫描电子显微镜（SEM）观察表明，OsMT2b 通过影响外皮层细胞的扩展来调节小穗颖壳的大小。组织学分析表明，OsMT2b 影响小穗颖壳横截面上的细胞数量，从而影响种子大小。从授粉后 6 天（DAP）到成熟，OsMT2b 过表达系种子的鲜重始终高于野生型（WT）和 RNAi 系种子，表明 OsMT2b 影响种子灌浆。反转录定量 PCR（RT-qPCR）分析表明，OsMT2b 调控与种子大小调控相关的活性氧清除相关基因的表达。综上所述，我们的结果表明 OsMT2b 正向调控种子大小，为利用遗传工程技术调控种子大小提供了新途径。
