Designer TALEs enable discovery of cell death-inducer genes

Area of Science:

• Plant Pathology
• Molecular Biology
• Genetics

Background:

• Transcription activator-like effectors (TALEs) are secreted by Xanthomonas bacteria to manipulate plant gene expression, influencing infection and resistance.
• The TALE PthA4AT, with a truncated DNA-binding domain, induces cell death in Nicotiana benthamiana, but its genetic targets remain unidentified.

Purpose of the Study:

• To identify plant genes targeted by the TALE PthA4AT that mediate cell death in N. benthamiana.
• To investigate the sequence specificity of PthA4AT-induced cell death.
• To explore the origin of TALE-dependent executor resistance genes.

Main Methods:

• Utilized TALE modularity to enhance specificity and reduce target sites.
• Performed sequence-specific substitutions within the TALE repeat region.
• Conducted transcriptome profiling and in silico target prediction.
• Identified and validated cell death inducer genes.

Main Results:

• PthA4AT-dependent cell death is sequence-specific.
• Stepwise modification of TALE repeats narrowed promoter recognition.
• Two novel cell death inducer genes were identified: one encoding a patatin-like protein, the other a bifunctional monodehydroascorbate reductase/carbonic anhydrase.
• These genes are not associated with known TALE-dependent resistance.

Conclusions:

• Aberrant expression of specific endogenous plant genes can trigger cell death.
• Supports the hypothesis that TALE-executor resistance genes can arise from diverse plant processes.
• Demonstrates TALEs as a tool for genome-wide screening of genes inducing specific phenotypes like cell death.