Acheampong, A.K., Institute of Plant Sciences, Department of Fruit Tree Sciences, Agricultural Research Organization, Volcani Centre, Bet Dagan, Israel, Institute of Plant Sciences and Genetics in Agriculture, Faculty of Agriculture, Food and Environment, Hebrew University of Jerusalem, Rehovot, Israel
Hu, J., Department of Biology, Duke University, Durham, NC, United States
Rotman, A., Institute of Plant Sciences, Department of Fruit Tree Sciences, Agricultural Research Organization, Volcani Centre, Bet Dagan, Israel
Zheng, C., Institute of Plant Sciences, Department of Fruit Tree Sciences, Agricultural Research Organization, Volcani Centre, Bet Dagan, Israel, Institute of Plant Sciences and Genetics in Agriculture, Faculty of Agriculture, Food and Environment, Hebrew University of Jerusalem, Rehovot, Israel
Halaly, T., Institute of Plant Sciences, Department of Fruit Tree Sciences, Agricultural Research Organization, Volcani Centre, Bet Dagan, Israel
Takebayashi, Y., RIKEN Plant Science Centre, Yokohama, Kanagawa, Japan
Jikumaru, Y., RIKEN Plant Science Centre, Yokohama, Kanagawa, Japan
Kamiya, Y., RIKEN Plant Science Centre, Yokohama, Kanagawa, Japan
Lichter, A., Institute of Postharvest and Food Sciences, Department of Postharvest Science of Fresh Produce, Agricultural Research Organization, Volcani Centre, Bet Dagan, Israel
Sun, T.-P., Department of Biology, Duke University, Durham, NC, United States
Or, E., Institute of Plant Sciences, Department of Fruit Tree Sciences, Agricultural Research Organization, Volcani Centre, Bet Dagan, Israel

Gibberellins (GAs) regulate numerous developmental processes in grapevine (Vitis vinifera) such as rachis elongation, fruit set, and fruitlet abscission. The ability of GA to promote berry enlargement has led to its indispensable use in the sternospermocarpic ('seedless') table grape industry worldwide. However, apart from VvGAI1 (VvDELLA1), which regulates internode elongation and fruitfulness, but not berry size of seeded cultivars, little was known about GA signalling in grapevine. We have identified and characterized two additional DELLAs (VvDELLA2 and VvDELLA3), two GA receptors (VvGID1a and VvGID1b), and two GA-specific F-box proteins (VvSLY1a and VvSLY1b), in cv. Thompson seedless. With the exception of VvDELLA3-VvGID1b, all VvDELLAs interacted with the VvGID1s in a GA-dependent manner in yeast two-hybrid assays. Additionally, expression of these grape genes in corresponding Arabidopsis mutants confirmed their functions in planta. Spatiotemporal analysis of VvDELLAs showed that both VvDELLA1 and VvDELLA2 are abundant in most tissues, except in developing fruit where VvDELLA2 is uniquely expressed at high levels, suggesting a key role in fruit development. Our results further suggest that differential organ responses to exogenous GA depend on the levels of VvDELLA proteins and endogenous bioactive GAs. Understanding this interaction will allow better manipulation of GA signalling in grapevine. © The Author 2015. Published by Oxford University Press on behalf of the Society for Experimental Biology.