Evidence That Plant-Like Genes in Chlamydia Species Reflect an Ancestral Relationship between Chlamydiaceae, Cyanobacteria, and the Chloroplast

↵Genes from Chlamydia pneumoniae CWL029 most similar to plant genes were identified using BAE-watch, with a step ratio of 1 and filtering any Chlamydial sequences (i.e., BAE-watch tertiary level) from the analysis. The same analysis was repeated with the other Chlamydia genomes to detect additional genes in this genus that are most similar to plant sequences. These nonstringent criteria identified all Chlamydia genes previously reported as having been horizontally acquired from plants. We propose that most of these plant proteins were originally of chloroplast origin and their similarity with Chlamydia sequences reflectsChlamydia's ancestral relationship with the bacterial ancestor of the chloroplast.

↵Chloroplast localization predicted by ChloroP (Emanuelsson et al. 1999), unless otherwise noted, and mitochondrial signal predicted by iPSORT (http://HypothesisCreator.net/iPSORT/)

↵Identified as horizontal gene transfer by Wolf et al. (1999a)

↵Identified as horizontal gene transfer by Royo et al. (2000)

↵Identified as horizontal gene transfer by Lange et al. (2000)

↵No prediction of a chloroplast transit peptide by ChloroP, however experimental evidence indicates that the protein is targeted to the chloroplast.

↵Chloroplast localization predicted by iPSORT but not ChloroP.

↵Incorrect start site appears to be predicted for protein. ChloroP predicts a transit peptide at start of sequence that shares similarity with all homologous proteins.

↵Phylogenetic analysis indicates Chlamydiaprotein not most related to plant protein.

↵Incorrect start site may be predicted (69 bp upstream) however this is uncertain so this protein represents the most interesting case in terms of potential gene transfer between bacteria and plants, or transfer between chloroplast and nuclear plant genomes that didn't involve targeting of the protein back to the chloroplast organelle.