Characterization of grape Gibberellin Insensitive 1 mutant alleles in transgenic Arabidopsis

Authors: Zhong, Gan-Yuan; Yang, Yingzhen

Submitted to: Transgenic Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/16/2011
Publication Date: 1/10/2012
Citation: Zhong, G., Yang, Y. 2012. Characterization of grape Gibberellin Insensitive 1 mutant alleles in transgenic Arabidopsis. Transgenic Research. 21:725-741.

Interpretive Summary: The GAI (GA insensitive) gene controls an important step in plant gibberellin signaling. Mutations in the gene can result in changes of plant architecture and other traits, thus providing potential opportunities for crop improvement. The best known example is the semi-dwarf wheat, a leading variety of the “green revolution” in the 1960s, which resulted from a single point mutation in the wheat GAI gene. As a step towards exploring GAI variants for the improvement of grapevines (Vitis vinifera), we evaluated and characterized the phenotypes of a dozen grape GAI mutants in transgenic Arabidopsis thaliana. These transgenic GAI mutant alleles were respectively under the control of 35S cauliflower mosaic virus promoter Arabidopsis GAI promoter and grape GAI promoter VvGAI. Our results demonstrated that different mutant forms of GAI can have very different impacts on the reduction of plant internodes length, therefore plant height, and changes of other traits. On the basis of the systematic evaluation of these grape GAI mutants in Arabidopsis, we concluded that the grape GAI mutant alleles mimicking the GAI mutant variants discovered in wheat, barley and Brassica could be potentially useful for the improvement of grapevine plant architecture.

Technical Abstract: We generated a dozen of different mutations in the grape Gibberellin Insensitive or GAI sequence, transformed them into Arabidopsis under the control of 35S, Arabidopsis or grape GAI promoter, and evaluated the impact of these mutant alleles on plant growth and development. These GAI sequence variants included some mimics of the known GAI mutant alleles discovered in grape, wheat, barley, corn, Brassica, and Arabidopsis. In general, plant height and its related traits such as length of internodes and inflorescences were significantly reduced for most of the mutant alleles studied, regardless of which promoters were 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 normal, dark green, and rarely curly. In addition, when certain GAI mutant alleles were under the control of the grape GAI promoter, the number of pods on inflorescences was significantly increased, but some of the pods produced few seeds due to partial sterility. Such wide range of trait variation resulting from the introduction of different GAI mutant alleles offers significant opportunities which have yet been well explored for crop improvement. On the basis of the systematic evaluation of various grape GAI mutants in Arabidopsis, we concluded that the grape GAI mutant alleles mimicking the GAI mutant variants discovered in wheat, barley and Brassica could be potentially useful for the improvement of grapevine plant architecture.