Department of Botany and Plant Pathology, Purdue University, 915 W State Street, West Lafayette, Indiana 47907, USA.
1] Department of Botany and Plant Pathology, Purdue University, 915 W State Street, West Lafayette, Indiana 47907, USA [2].
Nat Commun. 2014;5:3064. doi: 10.1038/ncomms4064.
Mediator is an evolutionarily conserved transcriptional regulatory complex. Mechanisms of Mediator function are poorly understood. Here we show that Arabidopsis MED18 is a multifunctional protein regulating plant immunity, flowering time and responses to hormones through interactions with distinct transcription factors. MED18 interacts with YIN YANG1 to suppress disease susceptibility genes glutaredoxins GRX480, GRXS13 and thioredoxin TRX-h5. Consequently, yy1 and med18 mutants exhibit deregulated expression of these genes and enhanced susceptibility to fungal infection. In addition, MED18 interacts with ABA INSENSITIVE 4 and SUPPRESSOR OF FRIGIDA4 to regulate abscisic acid responses and flowering time, respectively. MED18 associates with the promoter, coding and terminator regions of target genes suggesting its function in transcription initiation, elongation and termination. Notably, RNA polymerase II occupancy and histone H3 lysine tri-methylation of target genes are affected in the med18 mutant, reinforcing MED18 function in different mechanisms of transcriptional control. Overall, MED18 conveys distinct cues to engender transcription underpinning plant responses.
中介体是一个进化上保守的转录调控复合物。中介体功能的机制还了解甚少。在这里，我们表明拟南芥 MED18 是一种多功能蛋白，通过与不同的转录因子相互作用，调节植物的免疫、开花时间和对激素的反应。MED18 与 YIN YANG1 相互作用，抑制疾病易感性基因谷胱甘肽还原酶 GRX480、GRXS13 和硫氧还蛋白 TRX-h5。因此，yy1 和 med18 突变体表现出这些基因表达失调和对真菌感染的敏感性增强。此外，MED18 与 ABA INSENSITIVE 4 和 SUPPRESSOR OF FRIGIDA4 相互作用，分别调节脱落酸反应和开花时间。MED18 与靶基因的启动子、编码和终止子区域结合，表明其在转录起始、延伸和终止中的功能。值得注意的是，在 med18 突变体中，RNA 聚合酶 II 的占据和组蛋白 H3 赖氨酸三甲基化的靶基因受到影响，这加强了 MED18 在不同转录控制机制中的功能。总的来说，MED18 传递不同的信号，为植物反应的转录提供支持。
