甘蔗花叶病毒（SCMV）种群结构分析

摘要

针对已公布的18个甘蔗花叶病毒( SCMV)全基因组序列,利用MEGA 5.1分析了其11个蛋白( P1、HC-Pro、P3、6K1、CI、6K2、VPg、NIa-Pro、Nib、CP-C和多聚蛋白)编码基因所受的选择压,并结合其编码蛋白的功能,预测了部分基因在SCMV进化过程中的角色和变异位点.结果显示：P1和CP-N端的变异性程度较大,P1蛋白多样性最高；CP-C端变异性和多样性均较低；PIPO受到的选择压最小,但多样性最低,可能是由于PIPO与P3共用一段编码序列.来源于甘蔗的SCMV多聚蛋白的第2853、2897和2904个氨基酸位点(在CP中部)分别为T、R和E,而来源于玉米的SCMV多聚蛋白对应的氨基酸位点分别为S、K和D,表明这3个位点具有寄主依赖性.%The population structure and phylogenetic analysis were conducted on 18 fully sequenced Sugarcane mosaic virus ( SCMV) isolates. MEGA 5.1 was applied to evaluate the selective pressure of 11 genes encoding regions, i.e. P1, HC-Pro, P3, 6K1, CI, 6K2, VPg, NIa-Pro, Nib, CP-C and polyprotein. Basing on the known function of genes from Potyvirus genome, we predicted the potential roles and nucleotide substitutions sites of the 11 genes. The results were as following:P1 and N terminal of CP (CP-N) demonstrated the maximum variability while P1 showed the highest diversity among the tested SCMV isolates. However, the C terminal of CP (CP-C) displayed the minimum variability and diversity. PIPO was under the lowest selective pressure and diversity, which may be attribu-ted to PIPO sharing the same encoding region with P3. Also, the 2 853th, 2 897th and 2 904th amino-acid residues of the polyprotein from SCMV sugarcane isolates presented different patterns comparing to the isolates from maize. The corresponding amino-acid residues were T, R and E in the polyprotein of SCMV isolated from sugarcane, but S, K and D for those isolated from maize, respectively. The distinguished pattern of these three amino-acid residues sites demonstrated strong host preference.