Overexpression of rice acyl-CoA-binding protein OsACBP5 protects Brassica napus against seedling infection by fungal phytopathogens

Abstract Context. Class III acyl-CoA-binding proteins such as those from dicots (Arabidopsis and grapevine) play a role in defence against biotrophic pathogens. The overexpression of the monocot Oryza sativa (rice) OsACBP5 in Arabidopsis and rice has been demonstrated to enhance broad-spectrum disease resistance against selected phytopathogens in OsACBP5-overexpressing (OsACBP5-OE) lines. Aims. We aimed to develop transgenic rapid-cycling Brassica napus (B. napus-RC) and canola cv. Westar OsACBP5-OEs using tissue culture-based Agrobacterium-mediated transformation and to evaluate transgenic plants for resistance against Alternaria blight, blackleg and Sclerotinia rot diseases. Methods. Transgenic B. napus-RC and cv. Westar OsACBP5-OEs were generated through Agrobacterium-mediated transformation using Agrobacterium strain LBA4404 harbouring a plasmid with the rice complementary DNA encoding OsACBP5 driven by the cauliflower mosaic virus 35S promoter. Alternaria blight and blackleg pathogen assays were based on infecting young cotyledons, while detached leaf assay was used to test the tolerance of B. napus plants toward Sclerotinia sclerotiorum. Key results. Average transformation efficiencies of 24.2% and 29.1% were obtained for B. napus-RC and B. napus cv. Westar cotyledons respectively. OsACBP5-OE plants exhibited resistance 5 days after inoculation with Alternaria brassicae, 12 days after inoculation with Leptosphaeria maculans, and 24 h after inoculation with S. sclerotiorum. Conclusions. Transformation of B. napus-RC was shown herein to be an effective trait testing platform for canola. This study also provides an insight into the usefulness of OsACBP5 in enhancing resistance to necrotrophic phytopathogens. Implications. OsACBP5 can be overexpressed in other crops to generate pathogen-resistant varieties.