TAL evolution scripts

TAL effectors (aka TALEs) are repeat containing proteins found in the genus of phytopathogenic bacteria Xanthomonas. They are able to bind DNA through their repeat region and induce genes in the host plant. Thus variation in repeat number and order can lead to diversification of virulence functions and evasion of recognition by the host. Variation in TAL effector repeats and repeat sequence between different taxonomic groups has remained largely unexplored. In this study we describe the diversity found in a large set (957) of TAL effector sequences from 19 Xanthomonas pathovars and 3 groups of organisms containing TALE-like sequences, and we use this information to infer evolutionary mechanisms for TAL effectors. For this, we analyzed variation at three levels of organization in TAL effectors sequences: 1) the individual repeat level, 2) the TAL effector sequence level and 3) the repeat “motifs” level.