五味子DIR基因家族鉴定及特征分析

Identification and characterization of DIR gene family in Schisandra chinensis

Dirigent(DIR)蛋白在植物体内参与木质素、木脂素及棉酚的生物合成过程,并响应生物和非生物胁迫。该研究基于五味子全长转录组,利用生物信息学的方法对五味子DIR基因家族进行了初步的鉴定及蛋白理化性质、亚细胞定位、保守基序、系统进化和表达模式的分析。结果显示,共筛选得到34条五味子DIR基因,编码的氨基酸长度在156~387 aa,蛋白质理化性质存在一定差异,二级结构主要以不规则卷曲为主,半数的DIR蛋白定位于叶绿体中,其他DIR则定位于胞外、内质网、细胞质等区域;结合拟南芥、水稻、大豆等其他8个物种的DIR蛋白进行系统进化分析,结果显示所有DIR可以分成5个亚家族,五味子DIR在其中4个亚家族中呈不同数量的分布;通过对DIR-a亚家族的多序列比对,再次验证了该亚家族具有8个β折叠的独特结构;最后,通过分析五味子不同发育时期果实的转录组数据,初步明确了其表达模式,并结合不同时期果实中木脂素的含量积累,推测DIR与五味子木脂素合成的相关性,为五味子DIR基因的生物学功能研究和木脂素生物合成途径解析提供理论基础。

Dirigent(DIR)proteins are involved in the biosynthesis of lignin,lignans,and gossypol in plants and respond to biotic and abiotic stresses.Based on the full-length transcriptome of Schisandra chinensis,bioinformatics methods were used to preliminarily identify the DIR gene family and analyze the physico-chemical properties,subcellular localization,conserved motifs,phylogeny,and expression patterns of the proteins.The results showed that a total of 34 DIR genes were screened and the encoded proteins were 156-387 aa.The physico-chemical properties of the proteins were different and the secondary structure was mainly random coil.Half of the DIR proteins were located in chloroplast,while the others in extracellular region,endoplasmic reticulum,cytoplasm,etc.Phylogenetic analysis of DIR proteins from S.chinensis and the other 8 species such as Arabidopsis thaliana,Oryza sativa,and Glycine max demonstrated that all DIR proteins were clustered into 5 subfamilies and that DIR proteins from S.chinensis were in 4 subfamilies.DIR-a subfamily has the unique structure of 8β-sheets,as verified by multiple sequence alignment.Finally,through the analysis of the transcriptome of S.chinensis fruit at different development stages,the expression pattern of DIR was clarified.Combined with the accumulation of lignans in fruits at different stages,DIR might be related to the synthesis of lignans in S.chinensis.This study lays a theoretical basis for exploring the biological functions of DIR genes and elucidating the biosynthesis pathway of lignans in S.chinensis.