胡杨甜菜碱醛脱氢酶基因的功能分化

Functional divergence of betaine aldehyde dehydrogenase genes in Populus euphratica

摘要:

甜菜碱醛脱氢酶 (BADH) 在植物抗逆反应中发挥着重要作用。文中从胡杨cDNA克隆到2个甜菜碱醛脱氢酶基因，分别命名为PeBADH1和PeBADH2。PeBADH1和PeBADH2均编码503个氨基酸的蛋白质，预测分子量分别是54.93 kDa和54.90 kDa。组织表达模式分析发现这2个基因在正常生长、盐和H2O2胁迫下，在不同组织中的表达模式有较大差异。在大肠杆菌中表达并纯化了2个基因的重组蛋白。酶活性分析显示PeBADH1和PeBADH2蛋白对底物的活性分别是0.073 μmol/(min·mg) 和0.107 μmol/(min·mg)。热力学稳定性分析显示这2个蛋白的热力学稳定性具有明显差异。因此，基因表达模式差异与蛋白质酶学性质的不同预示着这2个基因可能存在功能上的分化。

Abstract:

Plant betaine aldehyde dehydrogenase (BADH) is a physiologically important enzyme in response to salt or drought stress. In this study, two BADH genes (PeBADH1 and PeBADH2) were cloned from Populus euphratica. Both PeBADH1 and PeBADH2 genes encode the proteins of 503 amino acid residues, with a calculated molecular mass of 54.93 kDa and 54.90 kDa, respectively. Reverse transcription PCR showed the divergence of expression pattern between the PeBADH1 and PeBADH2 genes in P. euphratica. The recombinant PeBADH1 and PeBADH2 proteins were overexpressed in E. coli, and purified by Ni-affinity chromatography. The PeBADH2 protein had 1.5-fold higher enzymatic activity towards the substrate aldehyde than PeBADH1 protein. The PeBADH1 protein revealed higher thermal stability than PeBADH2 protein. These results indicated obvious functional divergence between the PeBADH1 and PeBADH2 genes.