[Objective] The objective of this experiment was to further investigate the molecular characteristics of sorbitol dehydrogenase (SDH) in apple. [Method] The cDNAs and gDNAs of SDH gene family were isolated from the fruit of Malus domestica cv. Gala, and the mRNA expression levels of SDH gene family during leaf and fruit development were studied. [Result] Twelve cDNAs of SDH were cloned from apple fruit, in turn being named MdSDH7-MdSDHl8. Intron/exon structure analysis indicated that MdSDH18 contained 6 extons and 5 introns, whereas others contained 2 extons and 1 intron. The mRNA expression levels and enzyme activities of SDH were detected during leaf and fruit developments. According to the amino acid sequence homo logy, these SDHs were divided into two groups, A and B. During the fruit development, the mRNA expression levels of all SDHs at middle phase and late phase were higher than that of early phase, however, the changes of SDH enzyme activity were opposite to gene expression patterns. During leaf development, mRNA expression levels of A-SDH were in the order of young leaf > senescence leaf > mature leaf, with activities showing similar patterns to gene expression. However, mRNA expression levels of B-SDH was in the order of senescence leaf > mature leaf > young leaf. [Conclusion] These results further suggest that SDH is a gene family in apple, and the expression of gene family members shows different patterns during leaf and fruit developments.%[目的]进一步探明苹果中山梨醇脱氢酶(sorbitol dehydrogenase,SDH；EC 1.1.1.14)基因家族的分子特性.[方法]从‘嘎拉’苹果中克隆SDH基因家族全长cDNA序列和gDNA序列,检测它们在叶片和果实不同生长时期的表达模式.[结果]获得了12个苹果SDH基因家族cDNA序列,依次命名为MdSDH7-MdSDH18.除MdSDH18基因的全长gDNA序列由6个外显子和5个内含子组成,其余基因的全长gDNA序列由2个外显子和1个内含子组成.根据氨基酸序列相似性可以将这些SDH基因分为A和B两类.所有SDH基因在果实不同生长期均有表达,且中后期表达高于初期,但果实初期的SDH活性高于中后期.A类SDH基因在叶片不同生长时期的表达水平为幼叶＞衰老叶＞成熟叶,SDH活性也呈现出同样的趋势,但B类SDH基因在叶片不同生长时期的表达水平为衰老叶＞成熟叶＞幼叶.[结论]进一步证明了SDH基因在苹果中是以基因家族的形式存在的,且不同的基因家族成员在叶片和果实中有不同的表达特性.
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