A simple and efficient non-tissue culture method for genetic transformation of grape immature zygotic embryos via VvBBM overexpression

The process of genetic transformation of grapevine has long been hampered by the inefficiency and complexity of tissue culture-based methods, severely limiting cultivar improvement and functional genome research. In this study, we aimed to develop a novel, non-tissue culture-based method for the genetic transformation of grape immature zygotic embryos without relying on tissue culture. This approach involves the overexpression of the Vitis vinifera BABY BOOM ( VvBBM ) gene, a key member of the APETALA2/ETHYLENE RESPONSE FACTOR ( AP2/ ERF) ) transcription factor family, which is known to enhance plant regeneration and transformation efficiency. Using 'Cabernet Sauvignon' immature zygotic embryos, we achieved a transformation efficiency of 42.85 % under non-tissue culture conditions, significantly reducing the cycle duration to approximately two months compared to traditional genetic transformation methods. Phenotypic and molecular analyses of the transformed grapevine plants confirmed the integration and overexpression of the VvBBM gene, resulting in improved growth metrics, including increased plant height, root length, and total root number, in a genotype-independent manner. Our results highlight the potential of VvBBM overexpression to circumvent the limitations imposed by tissue culture dependence, providing a rapid, efficient, and scalable alternative to conventional methods. Our study not only provides a practical approach to overcoming the barriers to genetic transformation in grapevine, but also opens new avenues for the application of this technology in the breeding of other economically important crops.