Use of gene transfer technology for functional studies in grapevine

The understanding of the genetic determinism of plant phenotypes requires the functional annotation of genes governing specific traits including the characterisation of their regulatory networks. A striking feature of the grapevine genome and proteome lies in the existence of large families related to wine attributes that have a higher gene copy number than in other sequenced plants. During speciation, the appearance of new adaptive functions is often based on the evolution of orthologous genes eventually associated with duplication (paralogous sequences) leading to new proteins and expression profiles. The presence of original features in grapevine, including perennial status, vegetative architecture, inflorescence/tendril, flower organisation (corolla), and fleshy fruit of considerable acidity with various flavonoid compounds, makes functional genomics an essential approach to link a gene to a trait. For grapevine, the current lack of high throughput genetic techniques (e.g. induced mutant collections) and the difficulties associated with genetic mapping (allele diversity, chimerism, generation time) highlights the critical role of transgenic technology for characterising gene function. Different techniques are available to obtain information about gene functioning, but the choice of a particular approach depends on the process investigated (e.g. metabolism, developmental, pathogen response) and the experimental purpose (e.g. induction of ectopic functions, promoter studies, subcellular localisation). After a brief overview of the development of grapevine biotechnology, this paper reviews the state‐of‐the‐art gene transfer technology for grapevine and detailed examples of where transgenic technology has proven useful for studying gene function.