邓德力　王斌　曾长英　郭鑫　彭明

摘 要 在2个木薯品种中检测MeGSTU7基因在不同干旱胁迫阶段的表达量变化，并克隆测序了60个木薯品种的基因区DNA序列，分析基因核苷酸多态性及其自然变异，并将核苷酸多态性与干旱胁迫表型关联分析，挖掘优等位变异。结果表明，干旱胁迫条件下，2个品种的MeGSTU7的表达量均上调。MeGSTU7基因区核苷酸变异丰富，共有23个SNP位点，A/G突变为主；外显子区总计10个同义突变，12个非同义突变；外显子区在品种资源群体中有4种主要单倍型，所有的单倍型分为两大类，分子进化分析表明，MeGSTU7的外显子区的两端受到很强的正选择作用；Q+K+MLM混合线性模型关联分析结果表明，1个Indel和2个SNP与干旱胁迫下地上部鲜重耐旱系数显著关联，并筛选得到了优等位变异。

关键词 谷胱甘肽转移酶；MeGSTU7；木薯；抗旱；自然变异；单倍型

中图分类号 S533 文献标识码 A

Abstract Glutathione-S-transferase（GST）plays an important role in glutathione conjugation reaction and involves in many physiological and biochemical reaction in plants including stress resistance， primary metabolism and cellular signal transduction. MeGSTU7 codes GST in cassava（Manihot esculenta crantz）. In order to research the function of MeGSTU7 in drought-resisting， the expression quantity of MeGSTU7 was detected in two cassava varieties which are tolerant and sensitive to water stress in different degrees of drought stress. MeGSTU7 was cloned from 60 cassava varieties and sequenced. Sequceces were analyzed to study the single nucleotide polymorphism（SNP）and the natural variation. Correlation analysis between single nucleotide polymorphism and drought phenotype was made to select the excellent allelic variations. The results indicated that the expression of MeGSTU7 in two cassava varieties were up-regulated under drought stress. Nucleotide polymorphism in the gene regions of MeGSTU7 was abundant with 23 SNP among which the A/G mutation type was the major. There were 10 synonymous changes and 12 replacement changes in exon regions. All of the haplotypes were divided into two types among which 4 haplotypes were the major in population. Molecular evolution showed that intense positive selection function at the ends of the exon in MeGSTU7. By Q+K+MLM mixed linear model， one Indel and 2 SNP were significantly associated with the fresh weight of aerial parts in the stress of drought and excellent allelic variations were selected. In conclusion， this paper lays a good foundation for further research of the function of MeGSTU7 in drought resistant and the selection of excellent allelic variations.

Key words Glutathione-S-transferase； MeGSTU7； Cassava； Drought-resisting； Natural variation； Haploidtype

doi 10.3969/j.issn.1000-2561.2015.11.011

谷胱甘肽转移酶（glutathione-S-transferase， GST）在谷胱甘肽（glutathione， GSH）结合反应时起到关键作用，催化谷胱甘肽结合反应的起始。植物中，所有GSTs蛋白都是由2个25 ku亚基组成的蛋白二聚体，每一个GST亚基包含独立的催化位點[1]。谷胱甘肽转移酶超家族（GST）可根据蛋白序列相似性以及基因结构分为六大类：phi（F）、tau（U）、theta（T）、zeta（Z）、lambda（L）和dehydroascorbate reductase（DHAR）[2]。MeGSTU7蛋白属于tau（U）类，该类型谷胱甘肽转移酶是植物中所特有的[3]。

1.2.8 基因结构分析 在JGI数据库phytozome10（http：//phytozome.jgi.doe.gov/pz/portal.html）的木薯基因组序列，获得木薯品种AM560的MeGSTU7基因的CDS序列（coding sequence）以及DNA序列（genomic sequence），用NCBI的Spidey（http：//www.ncbi.nlm.nih.gov/IEB/Research/Ostell/Spidey/）分析其基因结构，并用DNAMAN软件绘制基因结构图。

1.2.9 序列多样性分析 利用MEGA4.0软件进行序列比对，对齐序列之后输出.MEG格式文件，然后导入DnaSPv5.0软件[21]分析MeGSTU7基因DNA序列的核苷酸多样性，包括SNP和Indel的数目及其在外显子，内含子，保守结构域的分布，同义突变和非同义替换。……