《植物生理学报》 2018, 54(10): 1576-1586

无籽蜜柚蔗糖合成酶(SUS)和蔗糖转化酶(INV)基因家族生物信息学及表达分析

邓舒雅, 麦贻婷, 陈惠萍, 钮俊^*

海南大学热带农林学院, 海口570228

通信作者：钮；E-mail: niujun5555@163.com

摘　要：

蔗糖是光合作用的最终产物, 通过韧皮部运输到植物的非光合组织中, 蔗糖的分解主要由蔗糖合成酶(SUS)和蔗糖转化酶(INV)催化。为了探究SUS和INV基因家族在无籽蜜柚汁胞发育中的功能, 本文通过HPLC研究, 结果表明阿拉伯糖和木糖在汁胞早期发育中含量较高, 而果糖、葡萄糖和蔗糖的含量随成熟过程显著增加。基于拟南芥数据库中SUS和INV蛋白序列, 与柚子的基因组数据进行同源比对, 分别筛选获得6个和12个具有完整开放阅读框(ORF)的Cg-SUS和Cg-INV基因。根据其在染色体上分布, 分别命名为Cg-SUS1~6和Cg-INV1~12, 并对其蛋白理化性质、内含子与外显子、系统进化树和蛋白功能结构域等方面加以分析。数字表达谱分析初步确定无籽蜜柚汁胞在发育过程中Cg-SUS2、Cg-SUS3和Cg-INV6转录较为活跃, 对其进行qRTPCR分析, 结合各类糖含量的检测结果与基因表达做相关性分析, 结果显示Cg-SUS2表达量与木糖、阿拉伯糖含量之间存在极显著正相关性, 因此Cg-SUS2可能涉及阿拉伯糖和木糖的生物合成; Cg-SUS3和Cg-INV6表达量与葡萄糖、果糖、蔗糖含量之间存在显著正相关性, 说明Cg-SUS3可能参与到蔗糖的降解途径中, 从而促使转运过来的蔗糖生成UDP-葡萄糖和果糖, Cg-INV6可能是液泡己糖累积的关键酶。

关键词：无籽蜜柚; 汁胞发育; 蔗糖合成酶; 蔗糖转化酶

收稿：2018-07-16   修定：2018-09-29

资助：海南省自然科学基金面上项目(317045)和海南大学科研启动基金项目[KYQD(ZR)1701]。 * 通讯作者(niujun5555@163.com)。

Bioinformatics and expression analysis of the sucrose synthase (SUS) and invertase (INV) gene families in Citrus grandis ‘Seedless’

DENG Shu-Ya, MAI Yi-Ting, CHEN Hui-Ping, NIU Jun^*

Institute of Tropical Agriculture and Forestry, Hainan University, Haikou 570228, China

Corresponding author: NIU Jun; E-mail: niujun5555@163.com

Abstract:

Sucrose is the end product of photosynthesis. Upon translocation through the phloem to sinks, sucrose is degraded by either sucrose synthase (SUS) or invertase (INV). To study the functions of SUS and INV genes in Citrus grandis ‘Seedless’, we used HPLC analysis, and the results indicate that the contents of arabinose and xylose were higher in early development of C. grandis ‘Seedless’ juice sacs, while the contents of fructose, glucose and sucrose significantly increased during the ripening process. Based on Arabidopsis SUS and INV proteins, we used BLASTP to search the homologous protein in pomelo genome. A total of 6 Cg-SUS and 12 Cg-INV with complete open reading frame (ORF) were identified. Based on their positions on C. grandis chromosomes, genes were named as Cg-SUS1–6 and Cg-INV1–12, respectively. Additionally, the analysis on their physicochemical properties, intron and exon, phylogenetic tree, and amino acid functional domain were performed. The digital expression analysis indicated that Cg-SUS2, Cg-SUS3 and Cg-INV6 showed an active transcript in juice sacs during fruit development of C. grandis ‘Seedless’, and also their expression profiles were detected by qRT-PCR. Combined with the correlation analysis between the soluble sugar contents and the gene expressions, the results showed that the expression of Cg-SUS2 had established a close positive correlation between the contents of xylose and arabinose. So Cg-SUS2 might be involved in biosyntheses of arabinose and xylose. The expressions of Cg-SUS3 and Cg-INV6 had a close positive correlation between the contents of glucose, fructose and sucrose, suggesting that Cg-SUS3 may be involved in the degradation of sucrose, which is converted into UDP-glucose and fructose. And Cg-INV6 may be a key enzyme in vacuolar hexose accumulation.

Key words: Citrus grandis ‘Seedless’; juice sacs development; sucrose synthase; invertase