title: Molecular characterization of a mosaic locus in the genome of 'Candidatus Liberibacter asiaticus'.
abstract: BACKGROUND
  Huanglongbing (HLB) is a highly destructive disease of citrus production worldwide. 'Candidatus Liberibacter asiaticus', an unculturable alpha proteobacterium, is a putative pathogen of HLB. Information about the biology and strain diversity of 'Ca. L. asiaticus' is currently limited, inhibiting the scope of HLB research and control.
  
  
  RESULTS
  A genomic region (CLIBASIA_05640 to CLIBASIA_05650) of 'Ca. L. asiaticus' showing hyper-sequence variation or locus mosaicism was identified and investigated using 262 bacterial strains (188 from China and 74 from Florida). Based on the characteristic electrophoretic profiles of PCR amplicons generated by a specific primer set, eight electrophoretic types (E-types) were identified, six E-types (A, B, C, D, E, and F) in China and four E-types (A, C, G, and H) in Florida. The 'Ca. L. asiaticus' strains from China consisted predominately of E-type A (71.3%) and E-type B (19.7%). In contrast, the 'Ca. L. asiaticus' strains from Florida was predominated by E-type G (82.4%). Diversity of 'Ca. L. asiaticus' in China was also evidenced. Strains from the high altitude Yunnan Province consisted of five E-types with E-type B being the majority (62.8%), whereas strains from the low altitude coastal Guangdong Province consisted of only two E-types with E-type A as the majority (97.0%). Sequence analyses revealed that variation of DNA amplicons was due to insertion/deletion events at CLIBASIA_05650 and the downstream intergenic region.
  
  
  CONCLUSIONS
  This study demonstrated the genomic mosaicism of 'Ca. L. asiaticus' resulted from active DNA insertion/deletion activities. Analyses of strain variation depicted the significant inter- and intra-continent diversity of 'Ca. L. asiaticus'.
authors.affiliation: National Engineering Research Center for Citrus, Citrus Research Institute, Southwest University, Chongqing 400712, People's Republic of China.
authors.forename: Xuefeng
authors.initials: X
authors.lastname: Wang
authors.forename: Changyong
authors.initials: C
authors.lastname: Zhou
authors.forename: Xiaoling
authors.initials: X
authors.lastname: Deng
authors.forename: Huanan
authors.initials: H
authors.lastname: Su
authors.forename: Jianchi
authors.initials: J
authors.lastname: Chen
mesh_terms: D002681:China; D002957:Citrus / Q000382:microbiology*; D016000:Cluster Analysis; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D005431:Florida; D016680:Genome, Bacterial; D005838:Genotype; D054643:INDEL Mutation; D008969:Molecular Sequence Data; D058889:Molecular Typing; D010935:Plant Diseases / Q000382:microbiology*; D016133:Polymerase Chain Reaction; D011110:Polymorphism, Genetic; D012230:Rhizobiaceae / Q000235:genetics* / Q000302:isolation & purification; D017422:Sequence Analysis, DNA
chemical_list: D004269:DNA, Bacterial