苎麻小分子G蛋白Rac1基因的克隆及表达分析

Cloning and Expression Analysis of a Small G Protein Rac1 Gene cDNA from Boehmeria nivea(Linn.) Gaudich

植物Rac是植物中特有的小分子G蛋白,我们从苎麻转录组中获得一个小分子G蛋白基因cDNA的部分序列,设计引物后采用RT-PCR结合RACE技术克隆了该基因的cDNA。序列分析表明,所克隆的Rac1 cDNA全长为1 043 bp,包括594 bp开放阅读框、214 bp的3′端非编码区和235 bp的5′端非编码区,能编码一个197氨基酸的推导蛋白。该蛋白包含G蛋白典型的效应因子结合位点、GTP/GDP结合位点和碱性氨基酸区,C末端具有保守的异戊烯基化位点CSIL。采用半定量RT-PCR分析了该基因在5个苎麻品种及不同组织器官中的表达情况,结果表明Rac1基因在苎麻根、茎、叶中均有表达,其中在叶中的表达量最高。纤维木质素含量不同的品种中,Rac1基因的表达量存在明显差异。木质素含量高的品种具有较高的Rac1基因表达,表明该基因可能在苎麻木质素合成过程中发挥作用。

Rac small G proteins of plants belong to a unique subfamily named ROP （Rho-related GTPase from plants）. Here, a Rac protein gene was isolated from Boehmeria nivea by RT-PCR and RACE based on the sequence ofRac gene in B. nivea transcriptome. The cDNA was 1 043 bp, contained a 594 bp opening reading frame, a 3＇-untranslated region of 214 bp, 5＇-untranslated region of 235 bp and encoded a putative protein of 197 amino acids with molecular weight 21.65 kDa and isoelectric point 9.30. BnRacl contains four conserved domains for guanine nucleotide binding and GTPase activities, an effector domain, a polybasic region and a C-terminal motif for prenylation. Semi-quantitative RT-PCR analysis revealed that the transcript level of BnRacl was higher in leaves than those in other issues. Moreover, BnRacl gene showed the high transcript abundance in a variety with high lignin content in fiber. It turned out that BnRacl gene was likely involved in lignin biosynthesis in B. nivea.