title: Horizontal gene acquisition of Liberibacter plant pathogens from a bacteriome-confined endosymbiont of their psyllid vector.
abstract: he Asian citrus psyllid Diaphorina citri is a notorious agricultural pest that transmits the phloem-inhabiting alphaproteobacterial 'Candidatus Liberibacter asiaticus' and allied plant pathogens, which cause the devastating citrus disease called Huanglongbing or greening disease. D. citri harbors two distinct bacterial mutualists in the symbiotic organ called bacteriome: the betaproteobacterium 'Candidatus Profftella armatura' in the syncytial cytoplasm at the center of the bacteriome, and the gammaproteobacterium 'Candidatus Carsonella ruddii' in uninucleate bacteriocytes. Here we report that a putative amino acid transporter LysE of Profftella forms a highly supported clade with proteins of L. asiaticus, L. americanus, and L. solanacearum. L. crescens, the most basal Liberibacter lineage currently known, lacked the corresponding gene. The Profftella-Liberibacter subclade of LysE formed a clade with proteins from betaproteobacteria of the order Burkholderiales, to which Profftella belongs. This phylogenetic pattern favors the hypothesis that the Liberibacter lineage acquired the gene from the Profftella lineage via horizontal gene transfer (HGT) after L. crescens diverged from other Liberibacter lineages. K A/K S analyses further supported the hypothesis that the genes encoded in the Liberibacter genomes are functional. These findings highlight the possible evolutionary importance of HGT between plant pathogens and their insect vector's symbionts that are confined in the symbiotic organ and seemingly sequestered from external microbial populations.
authors.affiliation: Electronics-Inspired Interdisciplinary Research Institute (EIIRIS), Toyohashi University of Technology, Toyohashi, Japan ; Japan Collection of Microorganisms, RIKEN BioResource Center, Tsukuba, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Nakabachi
authors.affiliation: Department of Liberal Arts, The Open University of Japan, Chiba, Japan.
authors.forename: Naruo
authors.initials: N
authors.lastname: Nikoh
authors.affiliation: Graduate School of Frontier Sciences, University of Tokyo, Kashiwa, Japan.
authors.forename: Kenshiro
authors.initials: K
authors.lastname: Oshima
authors.affiliation: Citrus Research Division, National Institute of Fruit Tree Science, Kuchinotsu, Japan.
authors.forename: Hiromitsu
authors.initials: H
authors.lastname: Inoue
authors.affiliation: Japan Collection of Microorganisms, RIKEN BioResource Center, Tsukuba, Japan.
authors.forename: Moriya
authors.initials: M
authors.lastname: Ohkuma
authors.affiliation: Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Tokyo, Japan.
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Hongoh
authors.affiliation: Center for Frontier Research, National Institute of Genetics, Mishima, Japan.
authors.forename: Shin-ya
authors.initials: SY
authors.lastname: Miyagishima
authors.affiliation: Graduate School of Frontier Sciences, University of Tokyo, Kashiwa, Japan.
authors.forename: Masahira
authors.initials: M
authors.lastname: Hattori
authors.affiliation: Bioproduction Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Japan.
authors.forename: Takema
authors.initials: T
authors.lastname: Fukatsu
mesh_terms: D000595:Amino Acid Sequence; D026905:Amino Acid Transport Systems / Q000737:chemistry / Q000235:genetics; D000818:Animals; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics; D023061:Gene Order; D022761:Gene Transfer, Horizontal; D016680:Genome, Bacterial; D006430:Hemiptera / Q000382:microbiology*; D054884:Host-Pathogen Interactions; D007303:Insect Vectors / Q000382:microbiology*; D008969:Molecular Sequence Data; D010802:Phylogeny; D012230:Rhizobiaceae / Q000145:classification / Q000235:genetics*; D016415:Sequence Alignment
chemical_list: D026905:Amino Acid Transport Systems; D001426:Bacterial Proteins