Crosstalk between Ethylene and ABA during changes in soil water content reveals a role of ACC in coffee anthesis regulation

O_LICoffee (Coffea arabica L.) presents an asynchronous flowering regulated by endogenous and environmental stimulus, and anthesis occurs once plants are rehydrated after a period of water deficit. C_LIO_LIWe evaluated the evolution of Abscisic Acid (ABA), ethylene, 1-aminocyclopropane-1-carboxylate (ACC) content, ACC oxidase (ACO) activity, and expression analysis of the Lysine Histidine Transporter 1 (LHT1) transporter, in roots, leaves and, flower buds from three coffee genotypes (Coffea arabica L. cv Oeiras, Acaua, and Semperflorens) cultivated under field conditions with two experiments. In a third field experiment, the effect of exogenous supply of ACC in coffee anthesis was evaluated. C_LIO_LIWe found an increased ACC level in all tissues from the three coffee genotypes in the re-watering period just before anthesis for all tissues and high expression of the LHT1 gene in flower buds and leaves. Ethylene content and ACO activity decreased from rainy to dry period whereas ABA content increased. Higher number of opened and G6 stage flower buds were observed in the treatment with exogenous ACC. C_LIO_LIThe results showed that the interaction of ABA-ACO-ethylene and intercellular ACC transport among leaves, buds, and roots in coffee favors an increased level of ACC that is most likely, involved as a modulator in coffee anthesis. C_LI