[目的]CAX(Ca2+/H+exchanger antiporter)是一类重要的跨膜转运蛋白,在植物体内阳离子转运上起着非常重要的作用.本文对苹果MdCAXs基因进行了生物信息学和组织特异性表达分析,以期为该类基因的功能研究奠定基础.[方法]利用生物信息学的方法对苹果MdCAXs基因家族染色体定位、蛋白质等电点、亲疏水性、跨膜区域、亚细胞定位及保守结构域进行了预测和分析,同时还分析了MdCAXs基因与其他物种CAXs基因的进化关系.采用实时荧光定量PCR法对苹果MdCAXs基因在不同盐处理下根、茎、叶中的表达变化进行分析.[结果]苹果MdCAXs家族包含8个成员,分别属于CAXsⅠ型中的A亚型和B亚型,编码436~817个氨基酸,等电点4.97~7.12,且都为疏水性蛋白;所有MdCAXs基因编码的氨基酸都有11个及以上的跨膜区域,含有CAXs基因5个典型的功能域:N-端自抑制区域(NRR)、C-端功能区域、Ca2+功能域(CaD)、C功能域和D功能域.亚细胞定位预测MdCAXs主要是定位在质膜和内质网上.苹果MdCAXs基因具有组织特异性表达特点,不同种类盐处理根、茎、叶中表达发生不同程度的变化,反映了MdCAXs存在功能上的差异,对不同阳离子有特异性的应答反应.[结论]苹果MdCAXs是一类跨膜转运蛋白,具有植物CAXs基因典型的结构特征,根、茎、叶对不同的盐离子具有不同的表达响应.[Objectives]CAX(Ca2+/H+exchanger antiporter), as important membrane transport proteins, play an important role in cation transportation in plants. In this paper, bioinformatics and tissue-specific expression of MdCAXs genes were analyzed to lay a basis on their further functional identification. [Methods]The bioinformatical methods were employed to predict and analyze some bioinformatical parameters of MdCAXs, including chromosome location, isoelectric point, hydrophobicity/hydrophilicity, transmembrane region, subcellular localization and conserved structure domains. Phylogenetic analysis is performed among MdCAXs and some other CAXs from other plants. The expression level of MdCAXs genes in vegetative organs after the salt treatments was analyzed using quantitative real-time PCR. [Results]The results showed that MdCAXs genes family contained eight members, which were located in subtype A and subtype B of the CAXsⅠ. MdCAXs were hydrophobic proteins, containing 436-817 amino acids, and the isoelectric point(pI)were from 4.97 to 7.12. They generally had 11 or more transmembrane regions, and contained five regulatory domains, i.e.N-terminal autoinhibitory domains(NRR), C-terminal domains, Ca2+ domain(CaD), C domain and D domain. MdCAXs proteins were mainly localized in plasma membrane and endoplasmic reticulum by on-line predication of PSORT software. On the other hand, MdCAXs showed the different expression levels in roots, shoots and leaves in response to the Na+, Ca2+, Mg2+ and Mn2+ treatments, suggesting the different functions in ion transportation of MdCAXs. [Conclusions]Apple MdCAXs were transmembrane transporter proteins, possessed typical structural features of plant CAXs and responded differentially to diverse cations in different organs
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