Resistance to citrus canker induced by a variant of Xanthomonas citri ssp. citri is associated with a hypersensitive cell death response involving autophagy associated vacuolar processes

ROESCHLIN R.A.; FAVARO M.A; CHIESA M.A; ALEMANO S.; VOJNOV, ADRIAN ALBERTO; ATILIO CASTAGNARO; FILIPPONE M.P.; GMITTER F; GADEA J; MARANO MR.

MOLECULAR PLANT PATHOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2017 vol. 18 p. 1267 - 1281

1464-6722

Xanthomonas citri ssp. citri (X. citri) is the causal agent of Asiatic citrus canker, a49 disease that seriously affects most commercially important Citrus species worldwide.50 We have previously identified a natural variant, X. citri AT, that triggers a host51specific defense response in Citrus limon. However, the mechanisms involved in this52 canker disease resistance are unknown. In this work, the defense response induced by53 X. citri AT was assessed by transcriptomic, physiological and ultrastructural analyses54 and the effects on bacterial biofilm formation were monitored in parallel. We show55 that X. citri AT triggers a hypersensitive response associated with the interference on56 biofilm development and arrest of bacterial growth in C. limon. This plant response57 involves an extensive transcriptional reprogramming setting in motion cell wall58 reinforcement, oxidative burst and accumulation of salicylic acid (SA) and phenolic59 compounds. Ultrastructural analyses revealed subcellular changes involving the60 activation of autophagy-associated vacuolar processes. Our findings show the61 activation of SA-dependent defense in response to X. citri AT and suggest a62 coordinated regulation between SA and flavonoids pathways, which is associated with63 autophagy mechanisms that control pathogen invasion in C. limon. Furthermore, this64 defense response protects C. limon plants from disease upon subsequent challenges by65 pathogenic X. citri. This knowledge will allow to rationally exploit the plant immune66 system as a biotechnological approach to manage the disease.