番茄中Rpi-blb2同源基因的挖掘与鉴定

Discovery and identification of homology gene to Rpi-blb2 in tomato(Solanum lycopersicum)

关键词:  番茄, 晚疫病, 基因, 垂直同源, 进化分析

Key words:  tomato(Solanum lycopersicum), late blight, gene, orthologous, phylogenetic analysis

摘要:

番茄晚疫病是番茄生产中的主要病害之一,经常会造成较大的经济损失。晚疫病生理小种的变异和进化常会导致番茄品种原有的遗传抗性丧失,因此不断挖掘新的抗性基因,改良番茄晚疫病抗性是番茄抗病育种的长期任务。该研究采用BLAST同源比对的方法,以马铃薯野生近缘种的晚疫病抗性蛋白序列Rpi-blb2为种子序列,在NCBI蛋白质序列数据库中检索得到11条番茄蛋白质序列,这些序列与种子序列相似性为78%～83%,属于番茄疾病抗性蛋白家族,并对该家族成员进行了基因结构、基因定位、序列保守结构域和进化关系等分析。结果表明:该家族中10条序列分布在第Ⅵ条染色体上,1条分布在第Ⅴ染色体上; 6号染色体上的10序列呈现2个抗病基因簇分布,在染色体上分别占据2个和3个基因位点; 10条同源蛋白是Rpi-blb2的共同垂直同源蛋白,但不具有平行同源关系,大多数成员定位于细胞质。按照蛋白质保守结构域和基因定位的不同可分为三类,第一类共4条系列,包含有DUF3542和NB-ARC两个保守结构域特征序列; 第二类共6条序列,与马铃薯Rpi-blb2蛋白一样,仅包含NB-ARC保守结构域特征序列,在这2类蛋白序列的NB-ARC结构域均位于序列中部; 第三类(仅包含XP_004239406.1)虽然也具有与第一类蛋白相似的DUF3542和NB-ARC结构域,但在结构域两端的非保守区序列较短,且位于5号染色体上,因此将其单独归为1类。前两类蛋白成员相应的基因具有1～2个内含子,第3类蛋白不含内含子。该研究结果为利用生物技术选育番茄抗性品种提供了理论基础。

Abstract:

Late blight is the most destructive disease in tomato(Solanum lycopersicum)cultivation worldwide and will result in large economic losses. As the variation and evolution of original races, mining new resisitance gene and improving the genetic resistance to late blight is a major issue in breeding new varieties of tomato, because of the new races will overcome the resistance gene-mediated genetic resistance from commercial varieties. Rpi-blb2, a potato late blight resistance protein as seed sequence, has 11 homology sequences from tomato protein sequences databank in NCBI and has a similarity to seed sequence range from 78%-83%. The above data were obtained by blast-protein way in this study. Then the gene structure, gene location, conserved domain feature of 11 protein sequences, and homology sequences of Rpi-blb2 belong to disease resistance protein sup-family of tomato and their evolution relationship were revealed and discussed. The results showed that ten of eleven distributed in the sixth chromosome, one the fifth chromosome; ten sequences distributed the sixth chromosome showed two gene clusters, containing two and three gene locus in the sixth chromosome, respectively. They were co-orthologous for Rpi-blb2 protein, but not paralogous each other, the most of them located in cytoplasm. According to the difference in structure domain and gene location, they were divided into three categories. The first category, a total of four members, contains DUF3542 and NB-ARC conser domain; The second category, a total of six members, like potatoes Rpi-blb2 protein, containing only NB-ARC conserved domain, the NB-ARC domain is located in the middle of these two kinds of protein sequences; The third category(only contains XP_004239406. 1)also has DUF3542 and NB-ARC domain and located on chromosome 5, but the non-conserved sequence at the ends of the domain is shorter. The members of the first two categories have one or two introns in gene structure, the third category does not contain introns. The study provides theory basis for breeding tomato disease resistance cultivar by molecular biology techniques.