Characterization and phylogenetic analysis of the Vitis vinifera gibberellin oxidases

Gibberellins (GAs) are phytohormones important to regulate several aspects of plant development, such as growth, flowering and fruit-set. GAs are used in viticulture to control berry size and bunch architecture, which are important traits that often determine the economic success of a grape variety. Despite the identification of 136 GA structures in nature, only a handful are biologically active. GA1 and GA4 are the most common bioactive GAs in grapevine and their pool is maintained through a combination of biosynthesis and deactivation activities, which involve a family of GA oxidases belonging to three distinct groups: GA 20-oxidase (GA20ox), GA 3-oxidase (GA3ox), and GA 2-oxidase (GA2ox). In this work we identified and characterized the family of grapevine GA oxidases, and identified six GA20ox, three GA3ox and eight GA2ox proteins, the latter further distinct into five C19-GA2ox and three C20-GA2ox proteins. Our phylogenetic analyses suggest a common origin of GA3ox and C19-GA2ox and challenge previous evolutionary models. The specific activity of the identified GA oxidases was confirmed in vitro by expression of the recombinant proteins, and in vivo by ectopic expression in the model species Arabidopsis thaliana