Characterization of grape Gibberellin Insensitive1 mutant alleles in transgenic Arabidopsis.

We generated 12 different mutations in the grape Gibberellin Insensitive1 (VvGAI1) sequences, transformed them into Arabidopsis under the control of 35S, Arabidopsis GAI or grape GAI1 promoter, and evaluated the impact of these mutant alleles on plant growth and development. These VvGAI1 sequence variants included some mimics of the known GAI-like mutant alleles discovered in grape, wheat, barley, corn, Brassica, and Arabidopsis. In general, plant height and related traits such as length of internodes and inflorescences were significantly reduced for most of the mutant alleles studied, regardless of which promoter was used. Interestingly, the numbers of rosette leaves and lateral branches were generally reduced when a 35S promoter was used to express the mutant alleles, but increased when an Arabidopsis or grape GAI promoter was used. Furthermore, the 35S plants often displayed curly and small leaves. In contrast, the leaves of the plants carrying mutant alleles controlled by a GAI promoter were of variable size, dark green and rarely curly. In addition, when certain VvGAI1 mutant alleles were under the control of the grape GAI1 promoter, the number of pods on inflorescences was significantly increased, but some of the pods produced few seeds due to partial sterility. On the basis of the systematic evaluation of various VvGAI1 mutant alleles in Arabidopsis, we concluded that the VvGAI1 mutant alleles mimicking the GAI or GAI-like mutant variants discovered in wheat, barley and Brassica could potentially be useful for the improvement of grapevine plant architecture.