地黄UDP-鼠李糖:鼠李糖基转移酶基因家族的生物信息学和表达分析

Bioinformatics and expression analyses of UDP-rhamnose:rhamnosyltransferase family in Rehmannia glutinosa

尿苷二磷酸鼠李糖基转移酶能将活性鼠李糖基供体转移到其糖基化受体分子上,合成鼠李糖基化的化合物.它们结构多样,活性广泛,具有药理、维持细胞结构、信号转导和化学防御及调节植物体内激素水平等重要作用.迄今,已从多种植物中分离得到这类酶,但有关其基因家族的结构特性与在植物次生代谢产物毛蕊花糖苷生物合成中的作用研究较少.以地黄尿苷二磷酸鼠李糖基转移酶基因(RgURT)家族的4个成员RgURT1~RgURT4为材料,利用生物信息学对该家族的特征进行了分析,比较了RgURT在高、低毛蕊花糖苷地黄品种块根中的表达模式.结果表明,其cDNA大小为645~1 422 bp,编码蛋白质分子量为24.05~53.24 kDa,由214~473个氨基酸残基组成,属于糖基转移酶GT-B型超家族,C端具有保守结构域盒(PSPG盒),无信号肽,亚细胞定位在细胞质中,二级结构以无规则卷曲和α-螺旋为主;RgURT4与RgURT1~RgURT3分别聚类为2个簇,RgURT4蛋白与其他3个URT蛋白序列之间的同源性低;RT-qPCR分析表明,RgURT基因在高毛蕊花糖苷地黄块根中的表达量高于低毛蕊花糖苷地黄块根中的表达量.研究首次揭示了地黄RgURT家族的特征,初步验证了RgURT与地黄毛蕊花糖苷合成相关,将为进一步研究毛蕊花糖苷合成提供了重要酶基因.

Rhamnosyltransferases can transfer active rhamnosyl donors to their rhamnosylated receptor molecules to synthesize rhamnosylated compounds with diverse structures and extensive activities.They play important roles in pharmacology,maintaining cell structure,signal transduction,chemical defense and regulating hormone levels in plants.So far,they have been isolated from many plants.However,few studies have been conducted on the structural characteristics of their gene families and their role in the biosynthesis of acteoside in plants.In this study,we used bioinformatics technology to analyze the structural characteristics of URT gene family in Rehmannia glutinosa(RgURT 1-RgURT 4),and their expression patterns in higher acteoside level variety and lower acteoside level variety were compared using its four members as materials.The results showed that their cDNA sizes were from 645 to 1422 bp,encoded from 214 to 473 amino acid residue-composed proteins with molecular weights from 24.05 to 53.24 kDa.They belonged to the GT-B superfamily of glycosyltransferases,had no signal peptide and a conserved domain box(PSPG box)at the C-terminal,and were localized in the cytoplasm.Their secondary structures mainly were random coil andα-Helix;RgURT4 and RgURT1-RgURT3 were clustered into two different groups,respectively,and the homology between RgURT4 protein and RgURT1-RgURT3 was low;RT-qPCR analysis showed that the expressions of three RgURT genes in the tuberous root of the high acteoside variety were higher than that in the low acteoside variety.This study revealed the structural features of RgURT family of Rehmannia glutinosa,and preliminarily verified the correlation between RgURT gene family and acteoside biosynthesis,and will provide candidate genes for further study of acteoside biosynthesis.