Phylogenetic reconstruction of the evolutionary relationships between the members of the PE protein family. The phylogenetic tree was constructed from the phylogenetic analyses done on the 110 aa N-terminal domains of the PE proteins. The tree was rooted to the outgroup, Rv3872 (PE35), shown to be the first PE insertion into the ESAT-6 (esx) gene clusters (region 1). The genes highlighted in purple, green and blue are present in ESAT-6 (esx) gene cluster region 1, 3 and 2, respectively. Genes highlighted in red are present in or have been previously shown to be duplicated from ESAT-6 (esx) gene cluster region 5  and genes highlighted in yellow are members of the PGRS subfamily of the PE family. Arrows indicate orthologues of genes identified to be present within the M. smegmatis genome sequence. Five sublineages (including the PE_PGRS subfamily) are indicated by Roman numerals.