State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, Guangdong Laboratory for Lingnan Modern Agriculture, Key Laboratory for Enhancing Resource Use Efficiency of Crops in South China, Ministry of Agriculture and Rural Affairs, College of Life Sciences, South China Agricultural University, Guangzhou, 510642, China.
Guangdong Provincial Key Laboratory of Utilization and Conservation of Food and Medicinal Resources in Northern Region, Shaoguan University, Shaoguan, 512005, China.
Plant J. 2024 Sep;119(6):2585-2598. doi: 10.1111/tpj.16910. Epub 2024 Jul 7.
Diurnal flower-opening time (DFOT), the time of spikelet opening during the day, is an important trait for hybrid rice (Oryza sativa L.) seed production. Hybrids between indica and japonica rice varieties have strong heterosis, but the parental lines usually have different, nonoverlapping DFOTs. This reduces the success of hybrid seed production in crosses between indica and japonica subspecies, thus hindering the utilization of indica and japonica inter-subspecies heterosis. However, little is known about the molecular mechanisms regulating DFOT in rice. Here, we obtained japonica rice lines with a DFOT 1.5 h earlier than the wild type by overexpressing OsMYC2, a gene encoding a key transcription factor in the jasmonate (JA) signaling pathway. OsMYC2 is activated by JA signaling and directly regulates the transcription of genes related to JA biosynthesis and cell wall metabolism. Overexpressing OsMYC2 led to significantly increased JA contents and decreased cellulose and hemicellulose contents in lodicule cells, as well as the softening of lodicule cell walls. This may facilitate the swelling of lodicules, resulting in early diurnal flower-opening. These results suggest that the OsMYC2-JA feedback loop regulates DFOT in rice via cell wall remodeling. These findings shed light on the understanding of regulatory mechanism of the DFOT of plants, which should promote the development of indica and japonica varieties suitable for hybrid rice breeding.
昼夜开花时间（DFOT），即白天小穗开花的时间，是杂交水稻（Oryza sativa L.）种子生产的一个重要特征。籼稻和粳稻品种之间的杂种具有很强的杂种优势，但亲本品系通常具有不同的、不重叠的 DFOT。这降低了籼稻和粳亚种间杂交种的制种成功率，从而阻碍了籼稻和粳亚种间杂种优势的利用。然而，人们对调控水稻 DFOT 的分子机制知之甚少。在这里，我们通过过表达编码茉莉酸（JA）信号通路关键转录因子的基因 OsMYC2，获得了 DFOT 比野生型早 1.5 小时的粳稻品系。OsMYC2 被 JA 信号激活，并直接调控与 JA 生物合成和细胞壁代谢相关的基因的转录。过表达 OsMYC2 导致小穗细胞中的 JA 含量显著增加，纤维素和半纤维素含量降低，小穗细胞壁变软。这可能有利于小穗的膨胀，从而导致早期昼夜开花。这些结果表明，OsMYC2-JA 反馈环通过细胞壁重塑来调节水稻的 DFOT。这些发现为理解植物 DFOT 的调控机制提供了线索，这应该会促进适合杂交水稻育种的籼稻和粳稻品种的发展。
