Capability of the plant-associated bacterium, Ensifer adhaerens strain OV14, to genetically transform its original host Brassica napus

Abstract

Land plants exist in intimate associations with complex microbial communities across the phyllosphere, endosphere, and rhizosphere, with the latter inhabited by microbes that establish relationships with their host extending from parasitism to mutualism. For example, the rhizospheric Agrobacterium tumefaciens is pathogenic across a broad host range while its related rhizobia Sinorhizobium meliloti is an important symbiont of plants. Of interest, both species have a recorded capacity to genetically transform plant species with variable success. In this regard they have been recently joined by the rhizospheric non-pathogenic bacterium Ensifer adhaerens OV14, which has demonstrated an ability to genetically transform both dicots (Arabidopsis thaliana, Nicotiana tabaccum, and Solanum tuberosum) and monocot (Oryza sativa). The goal of this study was to investigate the potential of E. adhaerens strain OV14 to genetically transform Brassica napus, the host species from which it was isolated. By tailoring current A. tumefaciens-based protocols to suit the growth parameters of E. adhaerens strain OV14, here we report the successful transformation of the commercial B. napus cultivar Delight. The results indicated that co-cultivating 5 day old cotyledonary petiole explants with E. adhaerens strain OV14 (OD600nm = 0.8) for 5 days in the presence of 200 µM acetosyringone delivered transgenic plants of morphological equivalence to the original treated cv. Delight. A transformation frequency of 4.0 ± 0.2 % was attained based on stable integration patterns recorded for T1 individuals, which indicated transgene integrations of 1–3 copies/line. Segregation analysis based on the inheritance of the nptII transgene in the T2 generation showed Mendelian and non-Mendelian segregation patterns for the designated kanamycin resistance phenotype. To conclude, this practical study highlights the expanding host range of Ensifer-mediated transformation by confirming the ability of the symbiont Ensifer adhaerens OV14 to genetically engineer its original host.