Department of Biological Sciences, Faculty of Science, National University of Singapore, Singapore, 117543, Singapore.
Temasek Life Sciences Laboratory, National University of Singapore, Singapore, 117604, Singapore.
Plant Cell. 2022 Jul 4;34(7):2730-2746. doi: 10.1093/plcell/koac110.
Glycogen synthase kinase 3 (GSK3) family members serve as signaling hubs for plant development and stress responses, yet the underlying mechanism of their transcriptional regulation remains a long-standing mystery. Here we show that the transcription of SHAGGY-like kinase 11/12 (SK11/12), two members of the GSK3 gene family, is promoted by the splicing factor SmD1b, which is essential for distributing carbon sources into storage and protective components in Arabidopsis seeds. The chromatin recruitment of SmD1b at the SK11/12 loci promotes their transcription associated with co-transcriptional splicing of the first introns in the 5'-untranslated region of SK11/12. The loss of SmD1b function generates transcripts with unspliced introns that create disruptive R-loops to hamper the transcriptional elongation of SK11/12, in addition to compromising the recruitment of RNA polymerase II to the SK11/12 genomic regions. These effects imposed by SmD1b determine the transcription of SK11/12 to confer a key switch of carbon flow among metabolic pathways in zygotic and maternal tissues in seeds.
糖原合酶激酶 3（GSK3）家族成员作为植物发育和应激反应的信号枢纽，但其转录调控的潜在机制仍然是一个长期存在的谜。在这里，我们表明，拼接因子 SmD1b 促进了 GSK3 基因家族的两个成员 SHAGGY-like kinase 11/12（SK11/12）的转录，SmD1b 对于将碳源分配到拟南芥种子的储存和保护成分中是必不可少的。SmD1b 在 SK11/12 基因座上的染色质募集促进了它们的转录，与 SK11/12 的 5'-非翻译区第一个内含子的共转录拼接相关。SmD1b 功能的丧失会产生带有未拼接内含子的转录本，这些内含子会产生破坏 R-环，从而阻碍 SK11/12 的转录延伸，此外还会损害 RNA 聚合酶 II 向 SK11/12 基因组区域的募集。SmD1b 施加的这些影响决定了 SK11/12 的转录，从而在种子的合子和母体组织中的代谢途径之间赋予了碳流的关键开关。
