Laboratory of molecular biology of tomato, Bioengineering College, Chongqing University, Chongqing, People's Republic of China.
Sci Rep. 2018 Feb 19;8(1):3285. doi: 10.1038/s41598-018-21679-1.
Mediator complex, a conserved multi-protein, is necessary for controlling RNA polymerase II (Pol II) transcription in eukaryotes. Given little is known about them in tomato, a tomato Mediator subunit 18 gene was isolated and named SlMED18. To further explore the function of SlMED18, the transgenic tomato plants targeting SlMED18 by RNAi-mediated gene silencing were generated. The SlMED18-RNAi lines exhibited multiple developmental defects, including smaller size and slower growth rate of plant and significantly smaller compound leaves. The contents of endogenous bioactive GA in SlMED18 silenced lines were slightly less than that in wild type. Furthermore, qRT-PCR analysis indicated that expression of gibberellins biosynthesis genes such as SlGACPS and SlGA20x2, auxin transport genes (PIN1, PIN4, LAX1 and LAX2) and several key regulators, KNOX1, KNOX2, PHAN and LANCEOLATE(LA), which involved in the leaf morphogenesis were significantly down-regulated in SlMED18-RNAi lines. These results illustrated that SlMED18 plays an essential role in regulating plant internode elongation and leaf expansion in tomato plants and it acts as a key positive regulator of gibberellins biosynthesis and signal transduction as well as auxin proper transport signalling. These findings are the basis for understanding the function of the individual Mediator subunits in tomato.
中介复合物是一种保守的多蛋白复合物，对于控制真核生物 RNA 聚合酶 II（Pol II）转录是必需的。由于人们对番茄中的中介复合物知之甚少，因此分离并命名了一个番茄中介亚基 18 基因，称为 SlMED18。为了进一步探索 SlMED18 的功能，通过 RNAi 介导的基因沉默靶向 SlMED18 的转基因番茄植物被生成。SlMED18-RNAi 系表现出多种发育缺陷，包括植株体型较小、生长速度较慢，以及复叶明显变小。SlMED18 沉默系中的内源性生物活性 GA 含量略低于野生型。此外，qRT-PCR 分析表明，参与叶片形态发生的赤霉素生物合成基因（如 SlGACPS 和 SlGA20x2）、生长素运输基因（PIN1、PIN4、LAX1 和 LAX2）以及几个关键调节因子（KNOX1、KNOX2、PHAN 和 LANCEOLATE（LA））的表达在 SlMED18-RNAi 系中显著下调。这些结果表明，SlMED18 在调节番茄植株节间伸长和叶片扩展中发挥重要作用，并且作为赤霉素生物合成和信号转导以及生长素适当运输信号的关键正调节剂发挥作用。这些发现为理解单个中介亚基在番茄中的功能提供了基础。
