PwEXP1在青杄种子萌发及逆境响应中的表达特征

Expression Characteristics of PwEXP1 Gene in Seed Germination and Adversity in Picea wilsonii

采用RACE-PCR技术,从青杄c DNA文库中克隆得到1个青杄Pw EXP1基因,其c DNA全长为1 186 bp,含777 bp的完整开放阅读框,编码259个氨基酸。生物信息学分析发现其理论分子量为27.90 k Da,等电点(p I)为8.07,N端有8个半胱氨酸残基,C端4个色氨酸残基,中部1个HFD结构域,具有扩展蛋白的典型结构。RT-q PCR试验显示Pw EXP1在青杄针叶中相对表达量较高。在种子萌发过程中,未开始萌发的种子表达量较低,萌发第2天和第4天表达量开始升高,萌发6天后达到较高水平。在逆境胁迫下,Pw EXP1在青杄根和叶中的表达模式不同。Na Cl和低温、高温胁迫均能增加Pw EXP1在根中的表达水平;PEG处理的渗透胁迫下,Pw EXP1在根中表达特征呈现前期下调、6 h后上调,而在叶中则在胁迫3 h和6 h时上调、9 h和12 h时下调、24 h时重新上调;在ABA处理后,Pw EXP1在根和叶中均表现下调。推测Pw EXP1在青杄种子萌发和逆境响应中发挥作用。

The PwEXP1 gene was cloned based on the cDNA library of Picea wilsonii and the EST sequence of PwEXP1 using RACE-PCR method in this study. The full length of PwEXP1 cDNA was 1 186 bp with an open reading frame （ORF） of 777 bp encoding 259 amino acids. Bioinformatics analysis revealed that the theoretical molecular weight of PwEXP1 was 27.68 kDa with isoelectric point （pI） of 8.07. The protein had a typical structure of the expansin protein： containing 8 conserved Cysteine residues at the N terminal, 4 Tryptophan at the C terminal and a HFD in the middle. With RT-qPCR and RT-PCR the temporal dynamics of expression were conducted. It was found that PwEXP1 gene was expressed in needle, root and stem. In the seed germination process, the expression level of PwEXP1 increased with the germination stage and peaked at 6 -10 days. Under different abiotic stress （NaC1, ABA, PEG, low and high temperature） , gene expression of PwEXP! was investigated by using RT-qPCR in roots and leaves. The expression level of PwEXP1 was up-regulated in root under NaC1, low and high temperature treatments. Under PEG-induced osmotic stress, the expression of PwEXP1 in roots was down-regulated at the early stage, and then induced after 6 h, while the expression showed an up-down-up trend in leaves. With ABA treatment, the expression of PwEXP1 was slightly repressed in both roots and leaves. The results suggest that PwEXP1 plays important roles in both seed germination and responses to abiotic stresses.