Complete genome sequence of citrus huanglongbing bacterium, 'candidatus liberibacter asiaticus' obtained through metagenomics

Yongping Duan, Lijuan Zhou, David G. Hall, Wenbin Li, Harshavardhan Doddapaneni, Hong Lin, Li Liu, Cheryl M. Vahling, Dean W. Gabriel, Kelly P. Williams, Allan Dickerman, Yijun Sun, Tim Gottwald

Research output: Contribution to journalArticlepeer-review

442 Scopus citations


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 a-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 plantcolonizing extracellular degradative enzymes. 'Ca. L. asiaticus' appears to have all type I secretion system genes needed for both multidrug efflux and toxin effector secretion. Multiprotein 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 α-proteobacteria that is both an intracellular plant pathogen and insect symbiont.

Original languageEnglish (US)
Pages (from-to)1011-1020
Number of pages10
JournalMolecular Plant-Microbe Interactions
Issue number8
StatePublished - Aug 2009
Externally publishedYes

ASJC Scopus subject areas

  • Physiology
  • Agronomy and Crop Science


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