大豆GolS基因家族鉴定及盐旱胁迫下的表达分析

Identification of soybean GolS gene family and analysis of expression patterns under salt and drought stresses

摘要:

肌醇半乳糖苷合成酶（galactinol synthase，GolS）是棉子糖家族寡糖（raffinose family oligosaccharides，RFOs）生物合成途径中的关键酶，在植物对非生物胁迫的反应中发挥重要作用。然而，关于大豆（Glycine max）GolS基因家族成员的分子结构特征还未见研究报道。本研究在全基因组水平上鉴定了6个大豆GolS基因家族成员，并对其理化性质、染色体定位、进化关系、基因结构、保守基序、二级结构、三级结构、组织特异性表达模式以及盐和干旱胁迫下的表达量进行了分析。结果表明：6个大豆GolS基因不均匀地分布在4条染色体上，6个大豆GolS蛋白的等电点为5.45-6.08，分子量变化范围为37 567.07-38 817.59 Da，氨基酸数量为324-339 aa；亚细胞定位预测结果发现4个蛋白定位在叶绿体上，2个蛋白定位在细胞质。系统进化树分析表明，大豆GolS基因家族成员在进化树中呈现出两两紧邻的现象，在进化上较为保守。6个基因成员含有的外显子数目为3或4。二级结构和三级结构预测表明，该家族所有成员蛋白质的空间结构主要由α螺旋和无规则卷曲结构组成，有较少的β转角结构和延伸链结构。组织特异性表达分析表明，6个GmGolS家族成员在种子、根、根毛、花、茎、豆荚、根瘤和叶中均有不同程度表达。基于qRT-PCR的表达分析显示，盐旱处理后所有GmGolS基因成员表现出不同程度的上调表达，表明这些基因可能与植物的耐盐抗旱响应有关。本研究结果为后续开展大豆GolS基因的功能解析奠定了基础。

Abstract:

Galactinol synthase (GolS) is a key enzyme in the biosynthetic pathway of raffinose family oligosaccharides (RFOs) and plays an important role in plant responses to abiotic stresses. However, the molecular characteristics of the GolS family members in soybean was not well-known. In this study, six members of GmGolS gene family were genome-widely identified, and their physicochemical properties, chromosomal localization, evolutionary relationship, gene structure, conserved motifs, secondary structure, tertiary structure, tissue-specific expression patterns and the expression levels under salt and drought stresses were analyzed. The results showed that six soybean GolS genes were unevenly distributed on four chromosomes, the range of the isoelectric points of six GmGolS proteins was 5.45-6.08, the molecular weight range was 37 567.07-38 817.59 Da, and the number of amino acids was 324-339 aa. The results of subcellular localization showed that 4 proteins were located in the chloroplast, and 2 proteins in the cytoplasm. Phylogenetic tree analysis showed that the members of the soybean GolS gene family were closely adjacent to each other, and were evolutionarily conservative. Six gene members contain 3 or 4 exons. Prediction of secondary and tertiary structures showed that the spatial structure of proteins of all family members was mainly composed of α-helix and random coil structure, with less β-turn and extended chain structure. Tissue-specific expression analysis showed that six GmGolS members expressed to variable degrees in seeds, roots, root hairs, flowers, stems, pods, nodules and leaves. Expression analysis based on qRT-PCR showed that all GmGolS genes showed different degrees of up-regulated expression under salt and drought treatment, indicating that these genes may be related to the response of plants to salt-tolerance and drought-resistance. These results may facilitate subsequent functional analysis of soybean GolS genes.