text_1: The repeat-variable diresidue (RVD) in the loop of Transcription-Activator Like (TAL) effectors specifies the nucleotides-amino acid contact at the target promoter element.
text_2: TAL (transcription activator-like) effectors, secreted by phytopathogenic bacteria, recognize host DNA sequences through a central domain of tandem repeats. Each repeat comprises 33 to 35 conserved amino acids and targets a specific base pair by using two hypervariable residues [known as repeat variable diresidues (RVDs)] at positions 12 and 13.