LAUSR

Plant hormones regulate growth, development, and defense against biotic and abiotic stresses. Salicylic acid (SA), ethylene (ET), and jasmonate (JA) are major phytohormones that control the defense against pathogens. SA and JA primarily regulate resistance against biotrophic and necrotrophic pathogens, respectively. NPR1 is the key regulator of SA signaling in plants. AtOZF1 function has recently been ascribed to promote both NPR1- dependent and -independent SA signaling. However, the role of AtOZF1 in JA signaling was not known. Here we report AtOZF1 as a positive regulator of JA signaling in Arabidopsis. The atozf1 mutants are more susceptible to the necrotrophic pathogen Botrytis cinerea than wildtype (WT) plants. AtOZF1 positively regulates the expression of JA inducible genes like PDF1.2 , VSP2 , THI2.1, and ORA59 . AtOZF1 takes part in SA-JA cross-talk to an extent similar to that of NPR1. AtOZF1 is essential for the activation of PDF1.2 expression upon exogenous methyl-jasmonate (MeJA) application. Intriguingly, SA can significantly promote MeJA-induced PDF1.2 expression in the absence of AtOZF1. Altogether our results reveal a novel SA-JA interaction pathway in plants.