Submitted to: American Phytopathological Society Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 5/15/2008
Publication Date: 6/1/2008
Citation: Doddapaneni, H., Liao,, H., Lin, H., Bai,, X., Zhao,, X., Civerolo, E.L. 2008. Comparative Phylogenomics and Multi-gene cluster analyses of the Citrus Huanglongbing (HLB)-associated bacterium Candidatus Liberibacter. American Phytopathological Society Annual Meeting. 98:S47. Interpretive Summary:
Technical Abstract: Candidatus Liberibacter is an alpha-protobacterium associated with citrus Huanglongbing (HLB). It is a serious threat to citrus production world-wide. Using molecular techniques, we have successfully cloned and characterized 27 Kbp of new genomic sequences from Ca. Liberibacter asiaticus (Las). Here we present comparative phylogenomic analyses of the newly cloned sequences from three genomic regions. Region-1 (gene cluster) has 12 genes, Region-2 (16S-23S) has full-length 16S and 23S rRNA genes, and Region-3 (OMP region) has 11 genes. We analyzed sequence variations among Ca. Las strains from China, Brazil, Florida and Japan, Ca. L. africanus (Laf) strains from South Africa and Ca. L. americanus (Lam) strains from Brazil for 16S region and rpoB gene. We identified pseudogenes, INDELs and SNPs in these cloned sequences. Phylogenetic analysis of the deduced protein sequences from the cloned regions characterizes Candidatus Liberibacter as a new clade in the sub-division of the a-proteobacteria, consistent with the 16S rRNA gene analyses. Molecular evolutionary clock estimation suggests monophyletic origin of the Candidatus Liberibacter species followed by speciation in conjunction with the continental drift theory. Comparative phylogenomic analysis of gene organization in Candidatus Liberibacter with members of the order Rhizobiales suggest overall gene structure and order conservation, albeit with minor variations including gene decay.