Diversity analysis of amp gene sequences in the 'Candidatus Phytoplasma meliae'

Phytoplasmas are plant pathogenic bacteria transmitted by insects. As endosymbiotic bacteria that lack a cell wall, their membrane proteins are in direct contact with host cytoplasm. In phytoplasmas the immunodominant membrane proteins (IDPs), are the most abundant proteins of the cell membrane. The antigenic membrane protein (Amp), one of the three types of IDPs, is characterized by a positive selection pressure acting in their extracellular domain. In South America, the Candidatus Phytoplasma meliae has been associated to chinaberry yellows disease. In the present work, we describe for the first time the structure, phylogeny and selection pressure of amp gene in sixteen Candidatus Phytoplasma meliae isolates. Our results indicate that amp gene sequences preserve the structure, large extracellular domain flanked by to hydrophobic domains in the N- (signal peptide) and C-termini (transmembrane), previously described in its orthologues and high divergence in the amino acids residues from extracellular domain. Moreover, a positive selection pressure was detected predominantly in this region confirming previous reports.