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

UVIEDO FACUNDO; CHIESA AMALIA; MARANO MARIA ROSA; MOLINA CELESTE; GADEA JOSE; GARCÍA LUCILA; ROESCHLIN ROXANA

CORDOBA

Congreso; XXXII Reunión Argentina de Fisiología Vegetal y XVI Congreso Latinoamericano de Fisiología Vegetal.; 2018

SOCIEDAD ARGENTINA DE FISOLOGIA VEGETAL

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 is 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 of 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