摘要：

RNA聚合酶Ⅱ相关因子Paf1(RNA polymerase Ⅱ associated factor 1)复合物是由6个亚基组成的真核生物重要的转录调控因子,其对特定基因的表达调控作用与植物的生长、发育和环境信号响应等生命活动密切相关。为探究小麦Paf1对逆境胁迫的响应特征,采用同源序列比对方法鉴定小麦的各Paf1亚基基因,通过mCherry融合蛋白的过表达和荧光显微观察鉴定各亚基蛋白的亚细胞定位,使用qRT-PCR方法分析各亚基基因对不同逆境胁迫的表达响应。结果表明,小麦Paf1的亚基TaVIP3、TaVIP4、TaVIP5、TaVIP6和TaPHP均由1套部分同源基因编码,其余1个亚基TaVIP2则由2套部分同源基因编码。植物VIP2的N端含有1个长度可变的富含脯氨酸残基区段,小麦的TaVIP2 还特有1个富含谷氨酰胺残基区段。TaVIP2、TaVIP4、TaVIP5和TaVIP6均为细胞核蛋白,而TaVIP3和TaPHP蛋白则可同时分布于细胞质和细胞核。各亚基基因在不同组织中的组成型表达差异模式相似,在叶片中的表达统一受高温胁迫的上调和高盐、干旱胁迫的下调。综上所述,小麦响应逆境胁迫的反应涉及对转录调控因子Paf1亚基基因表达水平的调节。

关键词: 小麦, Paf1复合物亚基, 亚细胞定位, 胁迫响应

Abstract:

The hexameric Paf1 (RNA polymerase Ⅱ associated factor 1) complex is a crucial transcription regulator in eukaryotes.Paf1-regulated expression of specific genes in plants is closely related to diverse biological processes including growth,development,and stress responses.In order to get information on the responses of Paf1 to abiotic stresses in common wheat,homologous sequence searches were performed to identify all of the genes encoding each of the Paf1 subunits in the wheat genome.mCherry fusions of the wheat Paf1 subunit proteins were expressed in protoplasts and tobacco leaves for determination of protein subcellular localization by fluorescence microscopy.qRT-PCR assays were conducted to profile the expression of wheat Paf1 subunit genes in response to different abiotic stresses.The results showed that,in wheat,five of the Paf1 subunits,TaVIP3,TaVIP4,TaVIP5,TaVIP6,and TaPHP,were each encoded by one set of homeologous genes while the sixth subunit TaVIP2 was encoded by two sets.Plant VIP2 sequences had an N-terminal proline-rich region with variable length,and wheat TaVIP2 sequences had an additional glutamine-rich region.Protein subcellular localization assays revealed the nuclear localization of TaVIP2,TaVIP4,TaVIP5,and TaVIP6 proteins and the nuclear and cytoplasmic localization of TaVIP3 and TaPHP proteins.Gene expression analyses revealed similar tissue-dependent constitutive expression variations and similar stress-induced expression patterns of wheat Paf1 subunit genes.These genes coordinately responded to the stress of high temperature by expression upregulation and to the stresses of salt and drought by expression downregulation.Collectively,our results suggested the involvement of expression regulation of Paf1 subunit genes in the responses of wheat to abiotic stresses.

Key words: Wheat, Subunit of the Paf1 complex, Subcellular localization, Stress response