小麦品种东农冬麦2号根中TaEXPA7部分同源基因的克隆及表达特性分析

膨胀素(expansin)是植物生长发育过程中诱导细胞壁松弛和伸展的蛋白,包括EXPA、EXPB、EXLA、EXLB四个基因家族,对植物根系的形成及快速发育具有重要作用。本试验以寒地冬小麦品种东农冬麦2号两叶一心期的根为材料,克隆了TaEXPA7基因的3个CDS全长,其氨基酸序列同源性较高,仅信号肽处有两个氨基酸不同,其核酸序列长度均为777bp,编码258个氨基酸,分别命名为TaEXPA7-A、TaEXPA7-B、TaEXPA7-D,且分别定位于2AL、2BL、2DL染色体。蛋白均含有DPBB-1和Pollen-allerg-1两个保守结构域,分子量为27 670.74Da,等电点为8.09,均为疏水性蛋白;与节节麦、二穗短柄草的相似性分别为99%和92%。采用两叶一心期的根进行qRT-PCR分析发现,TaEXPA7-A/B/D三个基因在根尖中的表达量均较高,伸长区和成熟区次之;对冬小麦根进行低温、干旱和激素处理后,这三个基因均下调表达,并且TaEXPA7-B基因的相对表达量较高,TaEXPA7-D的相对表达量较低。由此可见,多倍体小麦不同染色体上的基因在应对不同环境胁迫时,表达以及应答模式存在差异,并且在不同的环境胁迫下,发挥主导作用的染色体也存在差异;此外,该基因在根中的表达可能与低温、干旱以及外源激素的胁迫有一定的关系,可能是促进根系生长的重要基因。

Cloning and Characterization of TaEXPA7 Partial Homologous Genes in Roots of Winter Wheat Dongnongdongmai 2

Expansin is a protein that induces cell wall relaxation and elongation during plant growth and development, which contains EXPA, EXPB, EXLA and EXLB four gene families,playing an important role in the formation and rapid development of plant roots. In this experiment, the root of cold winter wheat Dongnongdongmai 2 at two leaf stage was used as the material to clone the three CDS full-length of the TaEXPA7 gene.Their amino acid sequences were highly homologous with only two different amino acids at signal peptide.The nucleic acid sequence length was 777 bp, encoding 258 amino acids.These three genes were named as TaEXPA7-A, TaEXPA7-B, TaEXPA7-D, located at 2AL, 2BL and 2DL chromosomes, respectively. The protein contained two conserved domains, DPBB-1 and Pollen-allerg-1, with molecular weight of 27 670.74 Da and isoelectric point of 8.09 and they were hydrophobic proteins. The similarity between them and Aegilops tauschii and Brachypodium distachyon was 99% and 92%, respectively. qRT-PCR analysis of roots of winter wheat at two leaves stage showed that TaEXPA7-A/B/D expressed higher in root tips, followed by elongation zone and mature zone. The winter wheat roots were treated with low temperature, drought and hormone and the three genes were all down regulated,the relative expression of TaEXPA7-B gene was higher and that of TaEXPA7-D was lower,which indicated that genes in different chromosomes of polyploid wheat responded differently to environmental stresses,their gene expression and response patterns were different, and the dominant chromosomes were also different under different environmental stresses. Moreover, the expression of these genes in roots may be related to stress such as low temperature, drought and exogenous hormones.They may be important gene for root growth.