Abstract
Alternate bearing consists in an irregular flowering and fruit load over consecutive years that produce important crop losses. In many fruit trees such as apple, alternate bearing is related to the floral induction and it is believed to be controlled by the phytohormone gibberellin (GA). GA acts as a potent promoter of floral induction in Arabidopsis by negatively regulating DELLA proteins, which in turn, inhibit the activity of floral promoter regulatory proteins. In perennial woody plant species, GA suppresses floral induction/initiation and DELLAs may act as co-activators of unknown floral promoter proteins. We are using a yeast-twohybrid approach to identify DELLA-interacting partners in apple and the glucocorticoid receptor system to define DELLAtranscription factor complexes target genes. By using these approaches, we expect to obtain a protein-protein interaction network around DELLA and shed light into its function in the control of the apple GA-mediated floral induction