14-3-3ε acts as a negative regulator of the response of Arabidopsis thaliana to Pst DC3000

14-3-3 proteins are a family of conserved proteins which are widely present as multiple isoforms in all eukaryotes. They play regulatory roles by interacting with phosphorylated protein clients thus affecting their stability, activity or subcellular localization. In plants, these proteins are involved in the regulation of carbon and nitrogen metabolism, gene expression, ion membrane transport, hormone signalling and in the response to abiotic stresses such as drought, cold, and salt stress. We investigated a possible role of 14-3-3 proteins in the response to biotic stresses by infecting Arabidopsis thaliana plants with the model plant pathogen Pseudomonas syringae pv. tomato (Pst) DC3000. Interestingly, the levels of the transcripts of the 14-3-3 isoforms analysed decreased upon infection, with the ԑ isoform displaying the strongest reduction. Therefore, we studied the effect of the 14-3-3 ԑ overexpression in the Arabidopsis response to Pst DC3000. In particular, we evaluated the bacterial growth in the plant tissue, the stomata closure, the callose deposition, the expression of disease-related genes, and the development of symptoms on leaves. Results show that the overexpression of 14-3-3ԑ provides Arabidopsis with a heightened sensitivity towards the pathogen; so, we suggest that this protein might act as a negative regulator of plant immunity, keeping it on hold and being promptly downregulated upon pathogen perception.