植物固醇合成途径关键基因CPI1的功能进化

Functional Evolution of Plant CYCLOPROPYL STEROL ISOMERASE1 Gene

固醇是真核生物膜的重要组分,在生长发育中具有重要作用。CPI1(CYCLOPROPYL STEROL ISOMERASE1)基因是植物特有的固醇合成途径基因,其编码产物为环丙基固醇异构酶。目前只有拟南芥(Arabidopsis thaliana)的CPI1基因被克隆并解析。研究发现,从藻类到高等开花植物中均存在单一拷贝的CPI1基因。陆生植物CPI1的基因结构及其所编码的氨基酸序列均高度保守,蛋白质序列相似性范围为48%-90%,但陆生植物CPI1与绿藻CPI1的蛋白序列之间存在显著差异。蛋白质结构预测发现CPI1具有非常相似的拓扑结构,均具有7个跨膜结构域和6个亲水环。组织表达模式分析显示,陆生植物CPI1在不同组织中均表达,是组成型表达基因。为了验证CPI1基因的功能,克隆了二穗短柄草(Brachypodiumdistachyon)BdCPI1基因,并转化拟南芥cpi1-1突变体。结果表明,BdCPI1能完全回补cpi1-1突变体的表型。基于单拷贝基因数目、保守的基因结构和蛋白质拓扑结构及基因表达模式,推测CPI1基因的功能可能在陆生植物中高度保守。

Sterols are major components of the eukaryotic membrane and play important roles in development processes.CYCLOPROPYL STEROL ISOMERASE1(CPI1) encodes a plant-specific key enzyme in the plant sterol biosynthesis pathway.Only the CPI1 from Arabidopsis has been cloned and characterized.In this study,we identified single-copy CPI1 genes from algae to flowering plants.All CPI1 genes from land plants have a conserved gene structure and high protein sequence similarity ranging from 48% to 90%,with low protein sequence similarity between land plants and algae.Protein structure prediction revealed that all CPI1 proteins have a similar protein structure,with 7 transmembrane domains and 6 hydrophilic loops.RT-PCR revealed that the land plant CPI1 genes were constitutive expression genes.To investigate the function of CPI1 genes,CPI1 from Brachypodium distachyon was cloned and transformed into the Arabidopsis cpi1-1 mutant.The BdCPI1 gene could completely complement the function of AtCPI.Thus,our data for single copy number,conserved gene structures,protein structures,and gene expression patterns suggest that the functions of land plant CPI1 genes are highly conserved.