Antimicrobial peptides expressed in wheat reduce susceptibility to Fusarium head blight and powdery mildew

Badea, A., Eudes, F., Laroche, A., Graf, R., Doshi, K., Amundsen, E., Nilsson, D. and Puchalski, B. 2013. Antimicrobial peptides expressed in wheat reduce susceptibility toFusariumhead blight and powdery mildew. Can. J. Plant Sci. 93: 199–208. Antimicrobial peptides (AMPs) have a broad spectrum of action against bacteria, fungi and viruses, which makes them attractive for building plant defense against a diversity of pathogens. Peptides MsrA2 and 10R were cloned in three genetic constructs for tissue-specific expressions in wheat, using either Lem1, GstA1WIR1a, or Ltp6 and LTP6 signal peptide targeting the lemma/palea, leaves and spikes, epicarp and endomembrane system, respectively. The minimal cassettes for these three genetic constructs and for Pat marker construct were co-delivered in immature wheat scutella using biolistics, and green plantlets were regenerated in presence of 5 mg L⁻¹ glufosinate. Molecular screening confirmed one regenerated plant carried and expressed all transgenes (AMP⁺): one copy of 10R driven by Ltp6 promoter, one copy of msrA2 driven by GstA1Wir1a and two copies of msrA2 driven by Lem1. Its offspring and T₃ generation were challenged with Fusarium graminearum and Blumeria graminis in a contained environment. A reduction of 50% in Fusarium head blight susceptibility was observed in T₁, and was inherited through T₃ generation. The latter, also presented a 53% reduction in Fusarium damaged kernels and 62% reduction in deoxynivalenol accumulation compared with wild cv. Fielder and sister lines AMP⁻. MsrA2 and 10R producing T₃ lines showed an average significant reduction of 59% in powdery mildew susceptibility compared with cv. Fielder. Synthetic MsrA2 and 10R peptides were effective as in vivo antifungal peptides in wheat. The expression of antimicrobial peptides in plant cells or tissues may have great potential to limit pathogen infection or growth protecting wheat against a diversity of fungal diseases.