HSI2 Repressor Recruits MED13 and HDA6 to Down-Regulate Seed Maturation Gene Expression Directly During Arabidopsis Early Seedling Growth
HSI2 Repressor Recruits MED13 and HDA6 to Down-Regulate Seed Maturation Gene Expression Directly During Arabidopsis Early Seedling Growth
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DOI：
10.1093/pcp/pcw095
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发表时间：
2016-08-01
影响因子：
4.9
通讯作者：
Chua, Nam-Hai
中科院分区：
文献类型：
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作者：
Chhun, Tory;Chong, Suet Yen;Chua, Nam-Hai
拟南芥HSI2(糖诱导基因2的高水平表达)携带EAR(ERF相关的两亲性抑制)基序，是种子成熟基因和脂类生物合成的抑制因子，而介体(MED)是一个保守的多蛋白复合体，将DNA结合的转录因子与RNA聚合酶II转录机制连接起来。HSI2是如何通过MED执行其抑制功能的，目前尚不清楚。在这里，我们证明了HSI2及其同系物HSI2-Lik(HSL1)能够形成同系和异质复合体。这两个因子都与MED13的TRAP240结构域结合，MED13是MED CDK8模块的一个亚基。Med13突变体的突变等位基因显示种子成熟基因的表达增加，子叶中的脂肪积累增加；相反，HSI2或MED13过表达的植株表现出相反的表型。在Med13和hsi2 hsl1中，HSI2和MED13的过表达表型分别被取消，表明这些功能共同需要HSI2和MED13。HSI2C-末端区域与HDA6相互作用，HDA6的过度表达也降低了种子成熟基因的表达和脂肪的积累。此外，HSI2、MED13和HDA6还与种子成熟基因的近端启动子和50个编码区结合。综上所述，我们的结果表明，HSI2招募MED13和HDA6来直接抑制种子萌发后成熟基因的一个子集。
Arabidopsis HSI2 (HIGH-LEVEL EXPRESSION OF SUGAR-INDUCIBLE GENE 2) which carries a EAR (ERF-associated amphiphilic repression) motif acts as a repressor of seed maturation genes and lipid biosynthesis, whereas MEDIATOR (MED) is a conserved multiprotein complex linking DNA-bound transcription factors to RNA polymerase II transcription machinery. How HSI2 executes its repressive function through MED is hitherto unknown. Here, we show that HSI2 and its homolog, HSI2-lik (HSL1), are able to form homo-and heterocomplexes. Both factors bind to the TRAP240 domain of MED13, a subunit of the MED CDK8 module. Mutant alleles of the med13 mutant show elevated seed maturation gene expression and increased lipid accumulation in cotyledons; in contrast, HSI2- or MED13-overexpressing plants display the opposite phenotypes. The overexpression phenotypes of HSI2 and MED13 are abolished in med13 and hsi2 hsl1, respectively, indicating that HSI2 and MED13 together are required for these functions. The HSI2 C-terminal region interacts with HDA6, whose overexpression also reduces seed maturation gene expression and lipid accumulation. Moreover, HSI2, MED13 and HDA6 bind to the proximal promoter and 50-coding regions of seed maturation genes. Taken together, our results suggest that HSI2 recruits MED13 and HDA6 to suppress directly a subset of seed maturation genes post-germination.