香蕉苹果酸脱氢酶基因克隆及其逆境胁迫表达

从香蕉果实抑制差减文库中获得一条香蕉苹果酸脱氢酶基因片段,采用RACE技术获得全长,命名为MaMDH;MaMDH基因全长1 249bp,编码332个氨基酸。生物信息学分析预测其编码蛋白分子量约35 448Da,等电点为6.53。与已知植物苹果酸脱氢酶基因相比,氨基酸同源性均达92%。保守结构域分析发现,MaMDH基因具有NAD结合位点、苹果酸结合位点和二聚体结合位点。系统进化树比对分析表明,MaMDH与玉米和小麦的亲缘关系较近。MaMDH基因在乙烯利处理香蕉苗中上调表达;在盐、Al 3+胁迫和香蕉尖孢镰刀菌4号生理小种处理幼苗中先上调表达,后下调表达;在冷害胁迫幼苗中先下调表达,后上调表达;而在干旱胁迫、伤害胁迫幼苗中表达没有明显变化。研究表明,香蕉中的苹果酸脱氢酶基因具有响应生物胁迫和非生物胁迫能力,可能在香蕉适应衰老、盐、铝、低温胁迫和枯萎病菌侵染等逆境中发挥重要作用。

Cloning and Expression Analysis of MaMDH in Banana under Environmental Stress

The cloning of an MDH cDNA,designated as MaMDH,was isolated from banana fruit by Suppression Subtractive Hybridization (SSH) and gained by RACE technique.The cDNA was 1 249 bp in length,coding for 332 amino acid residues.Predicted by bioinformatics analysis,its protein molecular weight is 35 448 Da,isoelectric point 6.53.Compared with the known plant malate dehydrogenase (MDH) gene,the homology of amino acid was 92%.By conserved domain analysis,the gene has NAD binding sites,malic acid binding sites,two dimer binding sites.Analyzed by phylogenetic tree,MaMDH are more closely related to corn and wheat.MaMDH stress expression analysis showed that the MaMDH expression of banana seedling dealt with ethephon upregulated,while dealt with salt and Al³⁺ stress,and banana fusarium oxysporum 4 races firstly upregulated,and then down-regulated.The MaMDH expression by chilling stress down-regulated firstly,and then upregulated.Under the drought stress and wounding stress,the expression of MaMDH did not change significantly.