title: Complete genome sequence of citrus huanglongbing bacterium, 'Candidatus Liberibacter asiaticus' obtained through metagenomics.
abstract: Citrus huanglongbing is the most destructive disease of citrus worldwide. It is spread by citrus psyllids and is associated with a low-titer, phloem-limited infection by any of three uncultured species of alpha-Proteobacteria, 'Candidatus Liberibacter asiaticus', 'Ca. L. americanus', and 'Ca. L. africanus'. A complete circular 'Ca. L. asiaticus' genome has been obtained by metagenomics, using the DNA extracted from a single 'Ca. L. asiaticus'-infected psyllid. The 1.23-Mb genome has an average 36.5% GC content. Annotation revealed a high percentage of genes involved in both cell motility (4.5%) and active transport in general (8.0%), which may contribute to its virulence. 'Ca. L. asiaticus' appears to have a limited ability for aerobic respiration and is likely auxotrophic for at least five amino acids. Consistent with its intracellular nature, 'Ca. L. asiaticus' lacks type III and type IV secretion systems as well as typical free-living or plant-colonizing extracellular degradative enzymes. 'Ca. L. asiaticus' appears to have all type I secretion system genes needed for both multidrug efflux and toxin effector secretion. Multi-protein phylogenetic analysis confirmed 'Ca. L. asiaticus' as an early-branching and highly divergent member of the family Rhizobiaceae. This is the first genome sequence of an uncultured alpha-proteobacteria that is both an intracellular plant pathogen and insect symbiont.
authors: USDA-ARS-USHRL, Fort Pierce, FL 34945, U.S.A. yonping.duan@ars.usda.gov
authors: Yongping
authors: Y
authors: Duan
authors: Lijuan
authors: L
authors: Zhou
authors: David G
authors: DG
authors: Hall
authors: Wenbin
authors: W
authors: Li
authors: Harshavardhan
authors: H
authors: Doddapaneni
authors: Hong
authors: H
authors: Lin
authors: Li
authors: L
authors: Liu
authors: Cheryl M
authors: CM
authors: Vahling
authors: Dean W
authors: DW
authors: Gabriel
authors: Kelly P
authors: KP
authors: Williams
authors: Allan
authors: A
authors: Dickerman
authors: Yijun
authors: Y
authors: Sun
authors: Tim
authors: T
authors: Gottwald
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics; D002352:Carrier Proteins / Q000235:genetics; D002957:Citrus / Q000382:microbiology*; D016680:Genome, Bacterial; D023281:Genomics / Q000379:methods; D006430:Hemiptera / Q000382:microbiology*; D008969:Molecular Sequence Data; D010802:Phylogeny; D012230:Rhizobiaceae / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D017422:Sequence Analysis, DNA; D013559:Symbiosis
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins