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

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.

An pair of an atypical NLR encoding genes confer Asian soybean rust resistance in soybean.

Asian soybean rust (ASR), caused by Phakopsora pachyrhizi, is a devastating disease that is present in all major soybean-producing regions. The limited availability of resistant germplasm has resulted in a scarcity of commercial soybean cultivars that are resistant to the disease. To date, only the Chinese soybean landrace SX6907 has demonstrated an immune response to ASR. In this study, we present the isolation and characterization of Rpp6907-7 and Rpp6907-4, a gene pair that confer broad-spectrum resistance to ASR. Rpp6907-7 and Rpp6907-4 encode atypic nucleotide-binding leucine-rich repeat (NLR) proteins that are found to be required for NLR-mediated immunity. Genetic analysis shows that only Rpp6907-7 confers resistance, while Rpp6907-4 regulates Rpp6907-7 signaling activity by acting as a repressor in the absence of recognized effectors. Our work highlights the potential value of using Rpp6907 in developing resistant soybean cultivars.