豆科抗病基因NBS-LRR进化的多基因组比对分析

Multiple Genome Alignment Analysis of the NBS-LRR Resistant Genes Evolution in Legume

NBS-LRR是植物抗病基因家族中一类重要的基因,根据编码的蛋白质氨基端的保守结构域不同,可分为CC-NBS-LRR和TIR-NBS-LRR两类基因。本研究在10个已测序豆科植物中对NBS-LRR进行序列比对,鉴定了各基因组中两类结构域基因的同源拷贝,发现在蒺藜苜蓿中包含1 207个NBS-LRR基因的同源拷贝,在10个基因组中同源拷贝数最多;并且其中88.2%的NBS-LRR基因是具有CC结构域。基因组同源共线分析,发现全基因组加倍有利于抗病基因拷贝数的扩增,为家族基因序列和功能多样化提供了创新资源。基于NBS-LRR基因系统发育分析,发现抗病基因存在大量串联重复,并基于进化树拓扑结构的变迁揭示抗病基因在不同的基因组中进化速率不同;另外,通过对旁系同源基因对间的核苷酸同义替换率(Ks)比较,进一步证实不同结构的抗病基因进化速率不同;同一结构的抗病基因在不同基因组中进化速率也表现有明显差异,与其他豆科物种相比,大豆抗病基因进化速率一直处于较低水平。研究结果为揭示抗病基因在豆科植物中的进化过程提供了重要的基因组信息学基础,对于在全基因组范围认识泛豆科抗病基因进化具有重要的意义。

NBS-LRR is an important resistance gene families in plants. According to the conserved domain of the amino terminus of the encoded protein, it can be divided into CC-NBS-LRR and TIR-NBS-LRR. In this study, the sequence alignment of NBS-LRR in 10 sequenced legume plants was carried out, and the homologous copies of two types of domain genes in each genome were identified. There were 1 207 homologous copies of NBS-LRR genes in barrel medic, and the number of homologous copies was the highest in 10 genomes, and 88.2% of NBS-LRR genes had CC domain. Genomic homologous collinear analysis showed that whole genome duplication was beneficial to the amplification of the copy number of the resistance genes, which provided innovative resources for the family gene sequences and function diversification. Based on the phylogenetic analysis of NBS-LRR genes, it was found that there were a large number of tandem duplication in the resistance genes, and the transition of the evolutionary tree topology reflected the different evolutionary rates of the resistance genes in different genomes. In addition, by estimating synonymous nucleotide substitutions at synonymous sites(Ks), it was further confirmed that the evolution rates of the different structure resistant genes were different. The evolution rate of resistance genes with the same structure in different genomes also showed significant differences.Compared with other legume species, the evolution rates of soybean resistance genes were always at a low level.The results provided an important genomic informatics basis for revealing the evolutionary process of resistant genes in legume plants, which would be of great significance for understanding the evolution of the resistance genes of pan legumes in the whole genome.