Uncovering Plant Growth-Mediating Allelochemicals Produced by Soil Microorganisms
نویسندگان
چکیده
Coevolving interactions between a plant population and its microbiota can potentially yield a rhizosphere enriched in metagenomes containing the blueprints for a vast array of natural products. We describe a method of isolating those metabolites through activity-based screening of soil metagenomic libraries. The method allows for the isolation of small molecules produced in vector– host expression systems containing large-insert DNA fragments extracted from the target plant rhizospheres. Allelopathic activities derived from selected clones were screened against a series of controls. Nonmetric multidimensional scaling (NMS) showed similar effects of the set of controls on lettuce growth, whereas annual bluegrass had a broader range of growth responses. Methanol extracts from clones indicating activity showed distinct patterns in grass seedling growth from the empty vector control, but the same extracts showed no effect on lettuce. The results indicate that the metagenomics method and bioassay screen of clone extracts are tools that can be used for initial determination of allelopathic activity from noncultured soil microbiota. Nomenclature: Annual bluegrass, Poa annua L.; lettuce, Lactuca sativa L.
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In his recent TREE news & comment, Watkinson1 drew attention to the role of soil microorganisms in plant population dynamics. In particular, he reported on the dynamical framework for the inter-relations between the composition of plant and soil communities, proposed last year by Bever et al.2 It is worth adding allelopathic interactions to this picture. Allelopathy has been defined by Rice3 as...
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