Liu Lei, Zhou Ying, Mao Feng, Gu Yujuan, Tang Ziwei, Xin Yi, Liu Fuxia, Tang Tang, Gao Hui, Zhao Xiangxiang
Jiangsu Key Laboratory for Eco-Agriculture Biotechnology Around Hongze Lake, Huaiyin Normal University, Huai'an, 223300, China.
Jiangsu Collaborative Innovation Center of Regional Modern Agriculture and Environment Protection, Huaiyin Normal University, Huai'an, 223300, China.
Rice (N Y). 2022 Jan 11;15(1):4. doi: 10.1186/s12284-022-00549-5.
Grain size is subtly regulated by multiple signaling pathways in rice. Alternative splicing is a general mechanism that regulates gene expression at the post-transcriptional level. However, to our knowledge, the molecular mechanism underlying grain size regulation by alternative splicing is largely unknown. GS3, the first identified QTL for grain size in rice, is regulated at the transcriptional and post-translational level. In this study, we identified that GS3 is subject to alternative splicing. GS3.1 and GS3.2, two dominant isoforms, accounts for about 50% and 40% of total transcripts, respectively. GS3.1 encodes the full-length protein, while GS3.2 generated a truncated proteins only containing OSR domain due to a 14 bp intronic sequence retention. Genetic analysis revealed that GS3.1 overexpressors decreased grain size, but GS3.2 showed no significant effect on grain size. Furthermore, we demonstrated that GS3.2 disrupts GS3.1 signaling by competitive occupation of RGB1. Therefore, we draw a conclusion that the alternative splicing of GS3 decreases the amount of GS3.1 and GS3.2 disrupts the GS3.1 signaling to inhibit the negative effects of GS3.1 to fine-tune grain size. Moreover, the mechanism is conserved in cereals rather than in Cruciferae, which is associated with its effects on grain size. The results provide a novel, conserved and important mechanism underlying grain size regulation at the post-transcriptional level in cereals.
水稻的粒型受多种信号通路的精细调控。可变剪接是一种在转录后水平调控基因表达的普遍机制。然而，据我们所知，可变剪接调控粒型的分子机制在很大程度上尚不清楚。GS3是水稻中首个被鉴定出的粒型数量性状位点，在转录水平和翻译后水平受到调控。在本研究中，我们鉴定出GS3存在可变剪接。GS3.1和GS3.2是两种主要的异构体，分别占总转录本的约50%和40%。GS3.1编码全长蛋白，而GS3.2由于保留了14个碱基对的内含子序列，产生了仅包含OSR结构域的截短蛋白。遗传分析表明，过表达GS3.1会减小粒型，但GS3.2对粒型没有显著影响。此外，我们证明GS3.2通过竞争性占据RGB1来破坏GS3.1信号通路。因此，我们得出结论，GS3的可变剪接减少了GS3.1的量，且GS3.2破坏了GS3.1信号通路，从而抑制GS3.1的负面影响以精细调控粒型。此外，该机制在谷类作物中保守，而在十字花科植物中不保守，这与其对粒型的影响有关。这些结果揭示了谷类作物在转录后水平调控粒型的一种新的、保守且重要的机制。
