Arabidopsis thalianaACS8 plays a crucial role in the early biosynthesis of ethylene elicited by Cu2+ ions.

Cu2+ ions are required by all living organisms and play important roles in many bactericides and fungicides. We previously reported that Cu2+ can elicit defense responses, which are dependent on the ethylene signaling pathway in Arabidopsis However, the mechanism by which Cu2+ elicits the biosynthesis of ethylene remains unclear. Here, we show that CuSO4 treatment rapidly increases the production of ethylene. In addition, it upregulates the expression of several defense-related genes and ethylene biosynthesis genes, including genes encoding S-adenosylmethionine synthase, 1-aminocyclopropane-1-carboxylate (ACC) synthase (ACS) and ACC oxidase. Among these genes, Arabidopsis thaliana (At)ACS8 was identified as essential for the defense response and early ethylene biosynthesis induced by Cu2+ Furthermore, Cu2+-induced AtACS8 expression depended on the copper-response cis-element (CuRE) in the promoter of AtACS8 Our study indicates that Cu2+ specifically activates the expression of AtACS8 to promote the early biosynthesis of ethylene that elicits plant immunity in Arabidopsis plants.