SUN gene is the major gene controlling fruit shape in tomato.In this study,we searched the grape sequence in NCBI,found the highest similar sequence of SUN gene in grape as compared with tomato and designed the specific primer.The cDNA of SUN gene,which is named VvSUN,is cloned by RT-PCR technique.Sequence analysis showed that the VvSUN gene contains a 1 278 bp open reading frame (ORF),which encodes a polypeptide of 425 amino acids with a calculated molecular weight of 48.11 kD and an isoelectric point of 10.63.Moreover,the data also indicated that VvSUN is a non-transmembrane and hydrophilic protein and most likely located in the nucleus and mitochondrial membrane,without signal peptide.Secondary structure analysis indicated that α-helix and random coil are the main structural elements in VvSUN protein.The amino acid sequence encoded by VvSUN gene has an IQ conserved domain,and the sequence similarity to other seven plants IQD family members in NCBI is 43%-53%.The phylogenetic tree showed that grape has the closest relationship with Arabidopsis thaliana IQD12 gene.According to these observations,we predicted that VvSUN protein in grape has similar functions with SUN protein in tomato.In addition,we performed quantitative real-time PCR (qRT-PCR) to determine the expression pattern of VvSUN in grape at different developmental stages and under gibberellin (GA3) treatments and used the vertical and horizontal diameters to evaluate the effects of GA3.Real-time PCR analysis revealed that the expression level of VvSUN gene showed the highest level at anthesis in two varieties,while maintained relatively low levels after anthesis.GA3 treatments markedly increased the fruit shape index,and pronouncedly enhanced the expression level of VvSUN gene in young fruit.Thus,our results suggested that the VvSUN gene in grape may be involved in the regulation of fruit elongation.%SUN基因是控制番茄果实形状的主效基因.该研究从NCBI中查找与番茄SUN相似性最高的葡萄序列,设计特异性引物,采用RT-PCR技术从'天山'葡萄花穗中克隆出该序列,命名为VvSUN基因.序列分析表明,VvSUN基因开放阅读框长度为1 278 bp,共编码425个氨基酸;预测蛋白质分子量为48.11 kD,理论等电点为10.63.VvSUN蛋白不具有信号肽,为非跨膜蛋白,可能定位于细胞核和线粒体膜上,属于亲水性蛋白;二级结构分析表明α螺旋和无规则卷曲是VvSUN蛋白中主要的结构元件.VvSUN基因编码的氨基酸具有IQ保守结构域,与NCBI中其他7种植物IQD家族成员基因序列相似性在43%~53%;系统进化树分析表明,VvSUN基因与拟南芥IQD12基因亲缘关系最近;推测葡萄VvSUN 蛋白质与番茄SUN 蛋白质具有相似的功能.荧光定量PCR分析表明,VvSUN基因在两个葡萄品种中均在盛花期表达量最高,花后果实中的表达量均较低;GA3处理后果实果形指数显著增大,且幼果中VvSUN基因表达量明显上升.研究推测葡萄VvSUN基因可能参与果形拉长的调控.
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