Generation of Composite Rosa roxburghii Plants with Transgenic Roots by Agrobacterium-Mediated Transformation

Abstract

Rosa roxburghii Tratt. is an emerging fruit endemic to China, which has the reputation of being the “King of Vitamin C” because of its abundance of vitamin C. However, it is also a recalcitrant species that imposes severe limitations on the transformation and whole-plant regeneration processes, restricting the verification of the functional genes. Therefore, developing a feasible and efficient genetic transformation method for R. roxburghii is an urgent requirement. Herein, K599 with eGFP was used as the Agrobacterium strain to optimize the genetic transformation from four factors: bacterial concentration, seedling age, infection site, and method. First, the original roots of 5-day-old seedlings were excised, and then the slant cuts of the remaining hypocotyls with 0.5 cm length were placed in K599 at an OD600 of 0.4. Subsequently, the explants were planted in a moistened sterile vermiculite after the beveled site was stained with a clump of bacteria. The results showed that the transformation efficiency of this cutting method was almost 28% at 30 days post-inoculation, while the transformation efficiency obtained by injecting 5-day-old seedlings 0.5–1.0 cm away from the primary root with K599 at an OD600 of 0.4 was only about 7%. Taken together, the current findings provide evidence that Agrobacterium-mediated transformation is a simple, fast, and efficient approach for generating composite R. roxburghii plants. Thus, this method has a broad application to analyze the gene functions in R. roxburghii and other related plant species.