The N2-fixing cyanobacterium Nostoc enters into symbioses with a wider variety of plants than any other bacterium. Symbiotic strains of Nostoc appear to be little specialized for their role; rather, they have been repeatedly domesticated by certain plants that have developed the ability to control cyanobacterial behavior and biochemistry. The special adaptations in plant partners are not investigated and understood owing to the absence of tools to support the molecular dissection of any host plant. An international group of researchers studying plant-cyanobacterial symbioses has resolved to develop a model plant partner system, but it is not clear at present which plant amongst the best-studied symbioses would be the most suitable as a model system for detailed investigations. This question will be answered by collaborative exploratory experiments designed to assess the ease with which each plant can be genetically manipulated and by a series of videoconference discussions among the researchers. The candidate plants are: the liverwart Blasia, the hornwart Anthoceros, the cycad (gymnosperm) Zamia, and the angiosperm Gunnera. Once a plant species is identified, a research plan for a preliminary proposal will be developed.
Less than 3% of world agricultural production comes from crops capable of associations with N2-fixing bacteria. Most other crops, most notably the grains, rely on nitrogenous fertilizer for highest yields, a practice both costly and damaging to the environment. Understanding the basis of plant-cyanobacterial symbioses may present the best chance to extend the benefits of biological nitrogen-fixation to crop plants outside the legumes. The experiments will be conducted through the exchange of students and material between U.S. and European laboratories of the consortium.
