TAL (transcription activator-like) effectors (often referred to as TALEs but not to be confused with the three amino acid loop extension family of proteins) are proteins secreted by Xanthomonas bacteria via their type III secretion system when they infect various plant species.
The hisB gene, found in the enterobacteria (such as E. coli), in Campylobacter jejuni and in Xylella/Xanthomonas encodes a protein involved in catalysis of two step in histidine biosynthesis (the sixth and eight step), namely the bifunctional Imidazoleglycerol-phosphate dehydratase/histidinol-phosphatase.