Department of Plant Science, Plant Genomics and Breeding Institute, and Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul 08826, Republic of Korea.
Department of Plant Molecular Systems Biotechnology, Crop Biotech Institute, Kyung Hee University, Yongin 17104, Republic of Korea.
J Exp Bot. 2017 Jul 10;68(15):4103-4114. doi: 10.1093/jxb/erx231.
In phototrophic plants, the highly conserved and tightly regulated process of chlorophyll (Chl) biosynthesis comprises multi-step reactions involving more than 15 enzymes. Since the efficiency of Chl biosynthesis strongly affects plant productivity, understanding the underlying regulatory mechanisms in crop plants can be useful for strategies to increase grain and biomass yields. Here, we show that rice (Oryza sativa) Phytochrome-Interacting Factor-Like1 (OsPIL1), a basic helix-loop-helix transcription factor, promotes Chl biosynthesis. The T-DNA insertion knockdown ospil1 mutant showed a pale-green phenotype when grown in a natural paddy field. Transcriptome analysis revealed that several genes responsible for Chl biosynthesis and photosynthesis were significantly down-regulated in ospil1 leaves. Using promoter binding and transactivation assays, we found that OsPIL1 binds to the promoters of two Chl biosynthetic genes, OsPORB and OsCAO1, and promotes their transcription. In addition, OsPIL1 directly up-regulates the expression of two transcription factor genes, GOLDEN2-LIKE1 (OsGLK1) and OsGLK2. OsGLK1 and OsGLK2 both bind to the promoters of OsPORB and OsCAO1, as well as some of genes encoding the light-harvesting complex of photosystems, probably promoting their transcription. Thus, OsPIL1 is involved in the promotion of Chl biosynthesis by up-regulating the transcription of OsPORB and OsCAO1 via trifurcate feed-forward regulatory loops involving two OsGLKs.
在光养植物中，叶绿素（Chl）生物合成是一个高度保守且受到严格调控的过程，涉及多步反应，涉及超过 15 种酶。由于 Chl 生物合成的效率强烈影响植物的生产力，因此了解作物中潜在的调控机制对于提高谷物和生物量产量的策略可能是有用的。在这里，我们表明，水稻（Oryza sativa）光受体相互作用因子样 1（OsPIL1），一种碱性螺旋-环-螺旋转录因子，促进 Chl 生物合成。在自然稻田中生长时，T-DNA 插入敲低 ospil1 突变体表现出淡绿色表型。转录组分析显示，ospil1 叶片中几个负责 Chl 生物合成和光合作用的基因显著下调。通过启动子结合和转录激活测定，我们发现 OsPIL1 结合到两个 Chl 生物合成基因 OsPORB 和 OsCAO1 的启动子上，并促进它们的转录。此外，OsPIL1 直接上调两个转录因子基因 GOLDEN2-LIKE1（OsGLK1）和 OsGLK2 的表达。OsGLK1 和 OsGLK2 都结合到 OsPORB 和 OsCAO1 的启动子上，以及一些编码光系统捕光复合物的基因上，可能促进它们的转录。因此，OsPIL1 通过涉及两个 OsGLKs 的三分支前馈调节环上调 OsPORB 和 OsCAO1 的转录，从而参与 Chl 生物合成的促进。
