Ectopic expression of MgSM1, a Cerato-platanin family protein from Magnaporthe grisea, confers broad-spectrum disease resistance in Arabidopsis

Proteins belonging to the newly identified Cerato-platanin (CP) family have been shown to have elicitor activity in inducing disease resistance responses in various plants. In this study, we characterized a gene, MgSM1, from Magnaporthe grisea, encoding a putative small protein belonging to the CP family. MgSM1 was constitutively expressed not only in different fungal growth stages but also during its infection process in rice plants. Agrobacterium-mediated transient expression of MgSM1 in Arabidopsis resulted in hypersensitive response in the infiltrated local leaves and enhanced disease resistance against Botrytis cinerea, and Pseudomonas syringae pv. tomato (Pst) DC3000 in upper leaves of plants, accompanyed by up-regulated expression of defense genes (PR-1, PR-5 and PDF1.2). Transgenic Arabidopsis plants expressing MgSM1 under control of a dexamethasone (DEX)-inducible promoter were generated. Expression of MgSM1 in transgenic plants was induced by exogenous application of DEX. MgSM1-expressing plants showed normal growth with application of <10 mu m DEX. After DEX induction, the MgSM1-expressing plants showed enhanced disease resistance against B. cinerea, Alternaria brassicicola and Psto DC3000 as well as up-regulated expression of some of defense genes. Moreover, accumulation of reactive oxygen species was observed in MgSM1-expressing plants. These results collectively suggest that ectopic expression of MgSM1 in transgenic plants confers broad-spectrum resistance against different types of pathogens. Our study also provides a novel strategy to generate environment-friendly crops with enhanced broad-spectrum resistance through ectopic expression of microbe-derived disease resistance-inducing proteins.