甜瓜α-葡萄糖苷酶和β-葡萄糖苷酶基因家族鉴定及表达模式分析

Identification and expression pattern analysis of α-glucosidase and β-glucosidase gene family members in melon

摘要:

葡萄糖苷酶是生物体糖代谢途径中不可或缺的一类酶。为探讨α-葡萄糖苷酶(α-glucosidase,AGLU)和β-葡萄糖苷酶(β-glucosidase,BGLU)的生物学功能及表达模式，对甜瓜基因组中的2个基因家族进行鉴定，对2个家族成员的数量、染色体位置、基因结构、亚细胞定位、蛋白保守基序、系统进化等进行分析，基于启动子顺式作用元件分析和蛋白互作预测模型对其功能进行了初步预测，并用实时荧光定量聚合酶链式反应(real time fluorescence quantitative polymerase chain reaction,qRT-PCR)技术对各成员的基因表达进行分析。结果表明，甜瓜中α-葡萄糖苷酶家族共有5个成员，分布于5条染色体上，全部成员均定位于细胞外基质，氨基酸长度为899−1 060 aa。甜瓜中β-葡萄糖苷酶家族共有18个成员，分布于8条染色体上，全部定位于细胞膜或细胞质中，氨基酸长度为151−576 aa。qRT-PCR结果表明，低温下约1/2基因表达受到抑制，其中CmAGLU5和CmBGLU7可能是2个家族中响应低温的关键基因。AGLU和BGLU家族基因受脱落酸(abscisic acid,ABA)、高盐和干旱胁迫诱导上调表达，其中AGLU家族中的CmAGLU3是响应ABA和高盐胁迫的关键基因，CmAGLU4是响应干旱胁迫的关键基因；BGLU家族中CmBGLU18是响应ABA的关键基因，CmBGLU6是响应高盐和干旱胁迫的关键基因。

关键词:甜瓜;α-葡萄糖苷酶;β-葡萄糖苷酶;非生物胁迫;表达模式

Abstract:

Glucosidases are an indispensable class of enzymes in the sugar metabolism of organisms. To investigate the biological functions and expression patterns of α-glucosidases (AGLUs) and β-glucosidases (BGLUs), we identified the two family members in the genome of melon (Cucumis melo). The number, location on chromosomes, gene structure, subcellular localization, conserved motifs, and phylogenetic relationship of the two family members were analyzed. Based on the cis-acting elements in the promoter region and protein interaction models, their functions were preliminarily predicted. Furthermore, the gene expression of the two family members was determined by qRT-PCR. The results showed that the melon genome contained five AGLU family members on five chromosomes, and all of the five members were located in the extracellular matrix, with the amino acid sequence lengths ranging from 899 aa to 1 060 aa. The melon genome carried 18 BGLU family members on 8 chromosomes, and all the members were located in the cell membrane or cytoplasm, with the amino acid lengths ranging from 151 aa to 576 aa. The qRT-PCR results showed that the expression of about 50% of the genes was down-regulated upon cold stress. CmAGLU5 and CmBGLU7 may be key members of the two families, respectively, in response to cold stress. The expression of all members of the two families was up-regulated under abscisic acid (ABA), high salt, and drought stress. In the AGLU family, CmAGLU3 was the key gene in response to ABA and high salt stress, while CmAGLU4 was the key gene in response to drought stress. In the BGLU family, CmBGLU18 was the key gene in response to ABA, while CmBGLU6 was the key gene in response to high salt and drought stress.

Key words:melon;α-glucosidase;β-glucosidase;abiotic stress;expression pattern