ARS | Publication request: Genome sequence of Candidatus Liberibacter asiaticus, the casual agent of citrus huanglongbing (greening)

Submitted to: National American Phytopathology Meetings
Publication Type: Abstract Only
Publication Acceptance Date: June 1, 2008
Publication Date: N/A

Technical Abstract: Citrus huanglongbing (HLB) is one of the most devastating diseases of citrus worldwide. The disease is associated with three different species of Candidatus Liberibacter: Ca. L. asiaticus (Las), Ca. L. americanus and Ca. L. africanus. We first detected and identified Las bacterium from HLB-infected pummelo in South Florida in August 2005 by PCR and sequencing confirmation using Las-specific primers. The disease has now spread throughout the state in both commercial and residential citrus. Due to its fastidious nature, the bacterium has not been cultured in vitro. We obtained and annotated a 17X draft genome for Ca. L. asiaticus using multiple displacement amplification and 454 pyrosequencing technologies from Las-infected Asian citrus psyllids (Diaphorina citri). The draft Las genome contained at least 1,161,087 base pairs with an average of 36% GC content, which were derived from 38 verified contigs raging from 5 kb to 116 kb. The draft genome was annotated to contain 3 rRNAs, 34 tRNA and 1077 open reading frames (ORFs), of which, 814 of the ORFs (75.6 %) had a functional assignment. Putative “toxin’ proteins and their type I secretion system were identified from the draft genome. The metabolite pathways and genome evolution of this unique a-proteobacterium, which is both an intercellular plant pathogen and insect parasite/symbiont, are also discussed.