摘要
Diacylglycerol acyltransferase （DGAT） is the key enzyme that catalyzes the triacylglycerol biosynthesis. The comparative analysis was performed on the DGAT1 genes of cotton and other model plants. Sequence analysis showed that most of the DGAT1 genes,with high variation of intron length and high conservation of intron phrase,from the cotton and other model plants had 16 exons. Additionally, 7 conserved motifs were present in these DGAT1 proteins. The core motifs were overlapped with the functional domain of DGAT1 protein. Phylogenetic analysis demonstrated that gene tree was highly consistent to species tree,suggesting that the evolutionary history of species was revealed by gene tree. There was single copy of DGAT1 gene in cotton,but at least two duplicated DGAT1 genes were iden- tified in rice,maize,poplar and moss genomes. The selective pressure analysis showed that the PtDGATla/PtDGATlb was under positive selection,but other four pairs of homologous genes were under negative selection. 17 positively selected sites were identified at subgroup level （P〉0.05）,suggesting these subgroups under relaxed functional constraint. The findings provide a basis for further studying func- tion and evolution of DGAT1 genes in cotton and other model plants.
二酰甘油酰基转移酶(DGAT)是催化三脂酰甘油生物合成的关键酶。对棉花与其他植物DGAT1基因进行鉴定与比较分析,序列分析结果表明,棉花与大多数模式植物DGAT1基因有16个外显子,内含子长度高度变异,但其相位极其保守;这些基因编码的蛋白具有7个保守基序,核心保守基序与功能结构域相互重叠。系统进化分析显示:基因树与物种树具有较高的一致性,DGAT1基因进化能真实反映物种系统发生关系;棉花DGAT1基因以单拷贝形式存在,但在玉米、水稻、杨树与小立碗藓中均存在至少两个DGAT1基因。选择压力检测结果显示:除了Pt DGAT1a/Pt DGAT1b受制于正选择作用外,剩余4对同源基因均受控于纯净选择;在基因亚群水平共检测到17个正选择位点,这说明在显著水平下各个亚群中均未检测到正选择位点。这些结果可为进一步研究棉花及植物DGAT1基因的功能提供基础。
基金
Supported by Youth Science Research Fund of Zhoukou Normal University in 2005(zknu B315213)
