苏云金芽胞杆菌LM1212菌株和突变株的全基因组序列比较分析  

Comparative analysis of two complete genome sequences from Bacillus thuringiensis strain LM1212 and its mutant

作　　者：佟蕾 张睿彬 彭琦[1] 张杰[1] Lereclus Didier 宋福平[1] TONG Lei;ZHANG Rui-Bin;PENG Qi;ZHANG Jie;Lereclus Didier;SONG Fu-Ping(State Key Laboratory for Biology of Plant Diseases and Insept Pests,Institute of Plant Protection,Chinese Academy of Agricultural Sciences,Beijing 100193,China;INRA,UMR1319 Micalis,Jouy-en-Josas 78350,France)

机构地区：[1]中国农业科学院植物保护研究所,植物病虫害生物学国家重点实验室,北京1001932 [2]INRA,UMR1319 Micalis,Jouy-en-Josas 78350,France

出　　处：《微生物学通报》2020年第6期1888-1900,共13页Microbiology China

基　　金：国家自然科学基金(31530095)。

摘　　要：【背景】LM1212菌株是昆虫病原菌苏云金芽胞杆菌(Bacillus thuringiensis,Bt)中的一员,其芽胞和晶体分别产生于芽胞形成细胞和晶体产生细胞中,具有独特的细胞分化表型。与野生株LM1212相比,突变株LM1212-DB芽胞细胞比例明显降低并产生更高比例的晶体产生细胞,这使得LM1212-DB菌株成为研究晶体产生细胞形成机制和提高菌株杀虫活性的绝佳实验材料。【目的】比较LM1212菌株和LM1212-DB菌株的基因组差异,以便于揭示导致这两个菌株表型差异的原因。【方法】利用单分子测序技术(single molecular real-time,SMRT)和Pacbio RS II测序平台对两个菌株进行全基因组测序,对染色体和质粒、双组分信号系统和插入序列等进行差异分析,并构建表型特性相关基因的系统发育树。【结果】基因组分析发现,LM1212和LM1212-DB菌株均含有丰富的插入序列和双组分信号系统,暗示两个菌株极易发生基因重排且具有较强的环境适应性。与LM1212菌株相比,突变株LM1212-DB中发生了染色体和质粒片段缺失、质粒重排、质粒拷贝数变异。进一步分析缺失基因的功能发现,一些环境胁迫响应基因(如sigB)和芽胞形成相关基因(如abrB)等缺失;通过分析质粒拷贝数变异发现,具有增加晶体细胞比例功能的转录因子CpcR所在质粒的拷贝数增加1个,同时对CpcR的进化分析发现,与其亲缘关系最近的基因的从属菌株也产生与LM1212菌株相似的细胞分化表型。这些重要功能基因的缺失和拷贝数变异可能是导致两个菌株表型差异的原因。此外,突变株LM1212-DB缺失I型限制-修饰系统,这使得突变株LM1212-DB与野生菌株LM1212相比具有更好的外源DNA兼容性。【结论】突变株LM1212-DB染色体和质粒的结构变异可能是导致与野生株LM1212表型差异的潜在原因,这将为研究LM1212菌株的晶体细胞分化机制提供指导方向。[Background]The LM1212 strain,a member of the insect pathogen bacterium Bacillus thuringiensis(Bt),has an unique cell differentiation phenotype that spores and crystals are produced in spore-forming cells and crystal-producing cells,respectively.Compared to the wild-type LM1212,the mutant strain LM1212-DB formed a reduced proportion of spore-forming cells and a higher proportion of crystal-producing cells,which provided an excellent experimental material for studying the mechanism of crystal-producing cell formation.[Objective]In this study,we tried to reveal the potential reason for the phenotypic difference between these two strains by investigating their genomic differences.[Methods]The whole genomes of the two strains were sequenced by using the single molecular real-time(SMRT)technology on the Pacific Bioscience(Pacbio)RS II sequencing platform.The differences in chromosome,plasmid,two-component system and insertion sequence between two strains were analyzed,and a phylogenetic tree based on a gene related to phenotypic characteristics was constructed.[Results]Genomic analysis showed that both strains contained abundant insertion sequences and two-component systems,suggesting that two strains were prone to rearrange genes for environmental adaptation.Fragment deletion within chromosome and plasmid,rearrangement and copy number variation for plasmid occurred in the mutant LM1212-DB.Some environmental stress response genes such as sigB and sporulation-related genes such as abrB were found to be absent and one copy number of plasmid carrying the transcription factor CpcR increased in the genome of LM1212-DB.The evolutionary analysis of CpcR indicated that the strain carrying the cpcR homologous gene also had a cell differentiation phenotype similar to that of LM1212.The deletion of these important functional genes and the decreasing of the copy number may be responsible for the phenotypic differences between the two strains.In addition,LM1212-DB lacked type I restriction-modification system,which might endow it

关 键 词：苏云金芽胞杆菌 基因组测序 比较基因组 表型差异 

分 类 号：S476.1[农业科学—农业昆虫与害虫防治]