title: Heterogeneic dynamics of the structures of multiple gene clusters in two pathogenetically different lines originating from the same phytoplasma.
abstract: Phytoplasmas are phloem-limited plant pathogens that are transmitted by insect vectors and are associated with diseases in hundreds of plant species. Despite their small sizes, phytoplasma genomes have repeat-rich sequences, which are due to several genes that are encoded as multiple copies. These multiple genes exist in a gene cluster, the potential mobile unit (PMU). PMUs are present at several distinct regions in the phytoplasma genome. The multicopy genes encoded by PMUs (herein named mobile unit genes [MUGs]) and similar genes elsewhere in the genome (herein named fundamental genes [FUGs]) are likely to have the same function based on their annotations. In this manuscript we show evidence that MUGs and FUGs do not cluster together within the same clade. Each MUG is in a cluster with a short branch length, suggesting that MUGs are recently diverged paralogs, whereas the origin of FUGs is different from that of MUGs. We also compared the genome structures around the lplA gene in two derivative lines of the 'Candidatus Phytoplasma asteris' OY strain, the severe-symptom line W (OY-W) and the mild-symptom line M (OY-M). The gene organizations of the nucleotide sequences upstream of the lplA genes of OY-W and OY-M were dramatically different. The tra5 insertion sequence, an element of PMUs, was found only in this region in OY-W. These results suggest that transposition of entire PMUs and PMU sections has occurred frequently in the OY phytoplasma genome. The difference in the pathogenicities of OY-W and OY-M might be caused by the duplication and transposition of PMUs, followed by genome rearrangement.
authors.affiliation: Laboratory of Plant Pathology, Department of Agricultural and Environmental Biology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan.
authors.forename: Ryo
authors.initials: R
authors.lastname: Arashida
authors.forename: Shigeyuki
authors.initials: S
authors.lastname: Kakizawa
authors.forename: Ayaka
authors.initials: A
authors.lastname: Hoshi
authors.forename: Yoshiko
authors.initials: Y
authors.lastname: Ishii
authors.forename: Hee-Young
authors.initials: HY
authors.lastname: Jung
authors.forename: Satoshi
authors.initials: S
authors.lastname: Kagiwada
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Yamaji
authors.forename: Kenro
authors.initials: K
authors.lastname: Oshima
authors.forename: Shigetou
authors.initials: S
authors.lastname: Namba
mesh_terms: D001483:Base Sequence; D031202:Chrysanthemum / Q000382:microbiology; D004251:DNA Transposable Elements / Q000235:genetics; D023061:Gene Order; D005798:Genes, Bacterial / Q000235:genetics*; D016680:Genome, Bacterial; D005810:Multigene Family / Q000235:genetics*; D010453:Peptide Synthases / Q000235:genetics; D010802:Phylogeny; D045582:Phytoplasma / Q000145:classification / Q000235:genetics* / Q000472:pathogenicity*; D016415:Sequence Alignment
chemical_list: D004251:DNA Transposable Elements; D010453:Peptide Synthases; C072322:lipoate-protein ligase