Enhancing disease resistance in poplar through modification of its natural defense pathway
Modification of the poplar defense pathway through pathogen-induced expression of an amphibian host defense peptide modulates plant innate immunity and confers robust and reliable resistance against a major poplar pathogen, Septoria musiva.
Host defense peptides (HDPs), also known as cationic antimicrobial peptides, represent a diverse group of small membrane-active molecules that are part of the innate defense system of their hosts against pathogen invasion. Here we describe a strategy for development of poplar plants with enhanced HDP production and resistance to the commercially significant fungal pathogen Septoria musiva. The naturally occurring linear amphipathic α-helical HDP dermaseptin B1, which has 31 residues and originated from the skin secretion of arboreal frogs, was N-terminally modified (MsrA2) and evaluated in vitro for antifungal activity and phytotoxicity. The MsrA2 peptide inhibited germination of S. musiva conidia at physiologically relevant low micromolar concentrations that were non-toxic to poplar protoplasts. The nucleotide sequence of MsrA2, optimized for expression in plants, was introduced into the commercial hybrid poplar Populus nigra L. × P. maximowiczii A. Henry (NM6) via Agrobacterium-mediated transformation. Transgene expression was regulated by the pathogen-inducible poplar promoter win3.12T, a part of the poplar innate defense system. Most importantly, the induced accumulation of MsrA2 peptide in poplar leaves was sufficient to confer resistance against S. musiva. The antifungal resistance of plants with high MsrA2 expression and MsrA2 accumulation was strong and reproducible, and without deleterious effects on plant growth and development. These results provide an insight into development of new technologies for engineering durable disease resistance against major pathogens of poplar and other plants.
KeywordsHost defense peptides MsrA2 win3.12T poplar promoter Populus nigra L. × P. maximowiczii A. Henry Septoria musiva Disease resistance
We thank Dr. Arun Goyal (University of Minnesota-Duluth, MN, USA) for providing plants of hybrid poplar P. nigra L. × P. maximowiczii A. Henry, genotype NM6; Dr. Brenda Callan (Pacific Forestry Centre, Victoria, BC, Canada) for providing the in vitro culture of Septoria musiva; Dr. C. Peter Constabel (University of Victoria, BC, Canada) for providing the fungus Melampsora medusae; Dr. Bob Chow (University of Victoria, BC, Canada) for helping with microscopy imaging; and Dr. Barbara Hawkins (University of Victoria, BC, Canada) for her kind support of this project.
D.Y. and S.M. designed the study, discussed and interpreted the results. DY conducted the experiments and wrote the manuscript. Both authors contributed to the final manuscript.
This study was funded by grants from the National Centre of Excellence, and the Advanced Foods and Materials Network to S.M.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
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