'Ca. Liberibacter asiaticus' proteins orthologous with pSymA-encoded proteins of Sinorhizobium meliloti: hypothetical roles in plant host interaction

Sinorhizobium meliloti strain 1021, a nitrogen-fixing, root-nodulating bacterial microsymbiont of alfalfa, has a 3.5 Mbp circular chromosome and two megaplasmids including 1.3 Mbp pSymA carrying nonessential 'accessory' genes for nitrogen fixation (nif), nodulation and host specificity (no...

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Bibliographic Details
Published in:PloS one 2012-06, Vol.7 (6), p.e38725-e38725
Main Authors: Kuykendall, L David, Shao, Jonathan Y, Hartung, John S
Format: Article
Language:English
Subjects:
Agriculture
Alfalfa
Alignment
Amino acids
Analysis
Apoptosis
Bacteria
Bacterial Proteins - genetics
Bacterial Proteins - metabolism
Biofilms
Biology
Biosynthesis
Cadmium
Cell surface
Cellular signal transduction
Cellular structure
Chaperonins
Chemical synthesis
Chromosomes
Citrus
Citrus fruits
Cofactors
Dehydrogenases
Diaphorina citri
DNA, Bacterial - genetics
Efflux
Electron transport
Enzymes
Gene expression
Genes
Genome, Bacterial
Genomes
Genomics
Gram-negative bacteria
Homeostasis
Homology
Host plants
Host specificity
Kinases
Laboratories
Ligands
Motility
Mycoplasma
Nitrogen
Nitrogen Fixation
Nodulation
Nucleotide sequence
Pathogens
pH effects
Phylogenetics
Plant pathology
Plants - microbiology
Plasmids - genetics
Potassium
Proteins
Rhizobiaceae
Rhizobiaceae - classification
Rhizobiaceae - genetics
Rhizobiales
Sequence Analysis, DNA
Sinorhizobium meliloti
Sinorhizobium meliloti - genetics
Soil microorganisms
Surface structure
Transduction
Tuberculosis
Vibrio cholerae
Xylella fastidiosa
Zinc
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Description
Summary:Sinorhizobium meliloti strain 1021, a nitrogen-fixing, root-nodulating bacterial microsymbiont of alfalfa, has a 3.5 Mbp circular chromosome and two megaplasmids including 1.3 Mbp pSymA carrying nonessential 'accessory' genes for nitrogen fixation (nif), nodulation and host specificity (nod). A related bacterium, psyllid-vectored 'Ca. Liberibacter asiaticus,' is an obligate phytopathogen with a reduced genome that was previously analyzed for genes orthologous to genes on the S. meliloti circular chromosome. In general, proteins encoded by pSymA genes are more similar in sequence alignment to those encoded by S. meliloti chromosomal orthologs than to orthologous proteins encoded by genes carried on the 'Ca. Liberibacter asiaticus' genome. Only two 'Ca. Liberibacter asiaticus' proteins were identified as having orthologous proteins encoded on pSymA but not also encoded on the chromosome of S. meliloti. These two orthologous gene pairs encode a Na(+)/K+ antiporter (shared with intracellular pathogens of the family Bartonellacea) and a Co++, Zn++ and Cd++ cation efflux protein that is shared with the phytopathogen Agrobacterium. Another shared protein, a redox-regulated K+ efflux pump may regulate cytoplasmic pH and homeostasis. The pSymA and 'Ca. Liberibacter asiaticus' orthologs of the latter protein are more highly similar in amino acid alignment compared with the alignment of the pSymA-encoded protein with its S. meliloti chromosomal homolog. About 182 pSymA encoded proteins have sequence similarity (≤ E-10) with 'Ca. Liberibacter asiaticus' proteins, often present as multiple orthologs of single 'Ca. Liberibacter asiaticus' proteins. These proteins are involved with amino acid uptake, cell surface structure, chaperonins, electron transport, export of bioactive molecules, cellular homeostasis, regulation of gene expression, signal transduction and synthesis of amino acids and metabolic cofactors. The presence of multiple orthologs defies mutational analysis and is consistent with the hypothesis that these proteins may be of particular importance in host/microbe interaction and their duplication likely facilitates their ongoing evolution.
ISSN:1932-6203
1932-6203
DOI:10.1371/journal.pone.0038725