Poster: Plant Pathogen/Symbiont Interactions
Abs #
748: Phylloplane components of Nicotiana tabacum: impact on the pathogen Peronospora tabacina, characterization, and site of synthesis
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Presenter: |
Shepherd, Ryan W, rwshep2@uky.edu |
Authors | Shepherd, Ryan W (A) Wagner, George J (A) | | Affiliations: |
(A): Plant Physiology/Biochemistry/Molecular Biology Program, Agronomy Dept., University of Kentucky, Lexington, KY 40546-0091 U.S.A.
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| Web Site: | http://www.uky.edu/~gjwagn2 | |
The plant phylloplane, or leaf surface, is a habitat characterized by complex interactions between the host plant and phyllosphere microorganisms. Plant secretions to the phylloplane contribute to innate host defense against pathogens. For example, exudate diterpenes in organic solvent washes of Nicotiana tabacum cv. TI 1068 leaves have been shown to inhibit Peronospora tabacina infection. We have discovered that leaf surface water washes of this tobacco inhibit P. tabacina infection on tobacco leaves and spore germination in vitro despite the fact that these contain only very low concentrations of diterpenes. Therefore, we examined the water wash for other components that could be responsible for the inhibitory effect. We found that leaf surface water washes contained prominent phylloplane proteins, including a family of previously uncharacterized 17-24 kD proteins that share a unique N-terminal sequence, and PR-5a protein, apparently the first PR-protein to be associated with the leaf surface. These proteins are present on sterile, greenhouse, and field-grown TI 1068 plants. We have collected varying amounts of similar proteins from several N. tabacum cultivars and other Nicotiana species. In TI 1068, phylloplane proteins are not produced by isolated trichome glands capable of diterpene and sugar ester biosynthesis. Also, tobacco mutants that lack trichome glands (TI 1112), or have glands but do not secrete exudate (TI 1406), produce phylloplane proteins. These proteins are not apparent in vascular fluid, yet their relative purity and abundance on the phylloplane suggest selective deposition. The role(s) of specific phylloplane proteins in blue mold inhibition and the mechanism of their deposition are currently being investigated.
