Molecular function of a new TAL effector from a variant of Xanthomonas citri subsp. citri that triggers defense response in host and non-host plants.

MOLINA M.C., ; CHIESA M.A.; MARANO M.R.; UVIEDO F.; FAVARO M.A., ; ROESCHLIN R; GARCÍA L., ; GADEA J.

Rosario

Jornada; Jornada Retreat IBR; 2019

IBR

Xanthomonas citri subsp. citri (X. citri) is the causal agent of Asiatic citrus canker. We have identified a natural variant, X. citri AT, that triggers a defense response in Citrus limon and C. sinensis. This response consists in a hypersensitive response (HR-like) associated with the interference on biofilm development and arrest of bacterial growth, involving an extensive transcriptional re-programming. The X. citri AT bacterial gene causing the deployment of HR-like responses in the plant appears to be a short variant of the pathogenic PthA4 TAL-effector, named PthA4AT. Transient expression of pthA4AT in the non-host Nicotiana benthamiana also induced HR phenotype. The function of this effector is mediating transcriptional activation of plant genes, as mutated version of the TAL effector in nuclear localization hampers the triggering of the HR-like response and the SV40 nuclear localization signal restores the HR response. DNA-binding assays using double-stranded microarrays indicate that this short TAL-effector is able to bind DNA. The identification of the gene responsible for the HR response is underway. This knowledge will help to rationally exploit the plant immune system as a biotechnological approach to manage citrus canker, and reveals biological functionality for short TAL-effectors.