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

Abstract

<p><strong>Context: </strong>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 <em>Oryza sativa</em> (rice) OsACBP5 in Arabidopsis and rice has been demonstrated to enhance broad-spectrum disease resistance against selected phytopathogens in OsACBP5-overexpressing (OsACBP5-OE) lines.</p><p><strong>Aims: </strong>We aimed to develop transgenic rapid-cycling <em>Brassica napus</em> (<em>B. napus</em>-RC) and canola cv. Westar OsACBP5-OEs using tissue culture-based <em>Agrobacterium</em>-mediated transformation and to evaluate transgenic plants for resistance against Alternaria blight, blackleg and Sclerotinia rot diseases.</p><p><strong>Methods: </strong>Transgenic <em>B. napus</em>-RC and cv. Westar OsACBP5-OEs were generated through <em>Agrobacterium</em>-mediated transformation using <em>Agrobacterium</em> strain LBA4404 harbouring a plasmid with the rice complementary DNA encoding OsACBP5 driven by the cauliflower mosaic virus <em>35S</em> promoter. Alternaria blight and blackleg pathogen assays were based on infecting young cotyledons, while detached leaf assay was used to test the tolerance of <em>B. napus</em> plants toward <em>Sclerotinia sclerotiorum</em>.</p><p><strong>Key results: </strong>Average transformation efficiencies of 24.2% and 29.1% were obtained for <em>B. napus</em>-RC and <em>B. napus</em> cv. Westar cotyledons respectively. OsACBP5-OE plants exhibited resistance 5 days after inoculation with <em>Alternaria brassicae</em>, 12 days after inoculation with <em>Leptosphaeria maculans</em>, and 24 h after inoculation with <em>S. sclerotiorum</em>.</p><p><strong>Conclusions: </strong>Transformation of <em>B. napus</em>-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.</p><p><strong>Implications: </strong>OsACBP5 can be overexpressed in other crops to generate pathogen-resistant varieties.</p>