TAL Effectors--pathogen Strategies and Plant Resistance Engineering

Transcription activator-like effectors (TALEs) from plant pathogenic Xanthomonas spp. and the related RipTALs from Ralstonia solanacearum are DNA-binding proteins with a modular DNA-binding domain. This domain is both predictable and programmable, which simplifies elucidation of TALE function in planta and facilitates generation of DNA-binding modules with desired specificity for biotechnological approaches. Recently identified TALE host target genes that either promote or stop bacterial disease provide new insights into how expression of TALE genes affects the plant–pathogen interaction. Since its elucidation the TALE code has been continuously refined and now provides a mature tool that, in combination with transcriptome profiling, allows rapid isolation of novel TALE target genes. The TALE code is also the basis for synthetic promoter-traps that mediate recognition of TALE or RipTAL proteins in engineered plants. In this review, we will summarize recent findings in plant-focused TALE research. In addition, we will provide an outline of the newly established gene isolation approach for TALE or RipTAL host target genes with an emphasis on potential pitfalls.