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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。
Plant Rac is a small G protein unique to plants. We obtained a partial sequence of a small G protein gene from the ramie transcriptome. After the primers were designed, the cDNA of the gene was cloned by RT-PCR and RACE. Sequence analysis showed that the full-length cDNA of Rac1 was 1 043 bp in length, including a 594 bp open reading frame, a 214 bp 3 ’non-coding region and a 235 bp 5’ non-coding region encoding a 197 amino acid deduced amino acid sequence protein. This protein contains a typical effector binding site of the G protein, a GTP / GDP binding site, and a basic amino acid region with a C-terminally conserved isopentenylation site, CSIL. The expression of Rac1 gene in five ramie varieties and different tissues and organs was analyzed by semi-quantitative RT-PCR. The results showed that Rac1 gene was expressed in the roots, stems and leaves of ramie, and the highest expression was in leaves. Among the varieties with different fiber lignin content, the expression level of Rac1 gene was significantly different. The higher lignin content had higher Rac1 gene expression, indicating that the gene may play a role in ramie lignin synthesis.