A fast and genotype-independent in planta Agrobacterium-mediated transformation method for soybean

Abstract

Efficient genotype-independent transformation and genome editing are highly desirable for plant biotechnology research and product development efforts. We have developed a novel approach to enable fast, high-throughput, and genotype-flexible Agrobacterium-mediated transformation using the important crop soybean as a test system. This new method is called GiFT (genotype-independent fast transformation) and involves only a few simple steps. The method uses germinated seeds as explants, and DNA delivery is achieved through Agrobacterium infection of wounded explants as in conventional in vitro-based methods. Following infection, the wounded explants are incubated in liquid medium with a sublethal level of selection and then transplanted directly into soil. The transplanted seedlings are then selected with herbicide spray for 3 weeks. The time required from initiation to fully established healthy T0 transgenic events is about 35 days. The GiFT method requires minimal in vitro manipulation or use of tissue culture media. Because the regeneration occurs in planta, the GiFT method is highly flexible with respect to genotype, which we demonstrate via successful transformation of elite germplasms from diverse genetic backgrounds. We also show that the soybean GiFT method can be applied to both conventional binary vectors and CRISPR-Cas12a vectors for genome editing applications. Analyses of T1 progeny demonstrate that the events have a high inheritance rate and can be used for genome engineering applications. By minimizing the need for tissue culture, the novel approach described here significantly improves operational efficiency while greatly reducing personnel and supply costs. It is the first industry-scale transformation method to utilize in planta selection in a major field crop.