There appears to be a one-to-one correspondence between the identity of two critical amino acids in each repeat and each DNA base in the target sequence.

These proteins are interesting to researchers both for their role in disease of important crop species and the relative ease of retargeting them to bind new DNA sequences.

Similar proteins can be found in the pathogenic bacterium Ralstonia solanacearum[3][4][1] and Burkholderia rhizoxinica,[5][1] as well as yet unidentified marine microorganisms.

Xanthomonas are Gram-negative bacteria that can infect a wide variety of plant species including pepper/capsicum, rice, citrus, cotton, tomato, and soybeans.

This competition between pathogenic bacteria and the host plant has been hypothesized to account for the apparently malleable nature of the TAL effector DNA binding domain.

[13] The second group (Boch) deduced the code through molecular analysis of the TAL effector AvrBs3 and its target DNA sequence in the promoter of a pepper gene activated by AvrBs3.

Numerous groups have designed artificial TAL effectors capable of recognizing new DNA sequences in a variety of experimental systems.

[14][16][17][18][19][20] Such engineered TAL effectors have been used to create artificial transcription factors that can be used to target and activate or repress endogenous genes in tomato,[16] Arabidopsis thaliana,[16] and human cells.

[17][19][9][21] Genetic constructs to encode TAL effector-based proteins can be made using either conventional gene synthesis or modular assembly.

[19][21][22][23][24][25][26][27] A plasmid kit for assembling custom TALEN and other TAL effector constructs is available through the public, not-for-profit repository Addgene.