| 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. |
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