Inositol hexakisphosphate as a key regulator of Nod factor induced calcium oscillations

Although the major part of our atmosphere, approximately 80%, is nitrogen gas (N2) the majority of crops plants grown in the world are unable to use the atmosphere as a source of this important nutrient. Compare this with carbon dioxide (CO2), present in the atmosphere at approximately 0.036 %, and utilised in photosynthesis, the process by which green plants use the energy of the sun to convert atmospheric CO2 into biomass, such as the sugars in sugar beet, or the starch in cereal grains and potato tubers. This biomass drives the production of amino acids, the individual units from which proteins are assembled. Amino acids not only contain high levels of carbon originating from CO2, but also high levels of nitrogen (N). These nitrogen atoms are as essential to the life of plants, microbes and animals as are carbon atoms. Indeed nitrogen is often the major limitation to plant growth and is the predominant ingredient in fertilisers that farmers apply to crops to increase production. Most plants take up nitrogen in the form of ammonia (NH3 or NH4+) or nitrate (NO3-) from the soil by their root system. Some soil bacteria are capable of converting, 'fixing', atmospheric nitrogen into ammonia. Plants belonging to the legume family, whose members include peas, beans, and clover form close interactions with these bacteria, whereby the bacteria live inside a specialised plant organ on the root called the nodule. In this symbiotic relationship the bacteria are encouraged to convert nitrogen into ammonia, which the plant utilises for growth and in return the plant provides nutrients including sugars for the bacteria inside the nodule. We are interested in the processes by which plant roots communicate with the nitrogen fixing-bacteria. Specialized single cells on the plant root, called hair cells, initially communicate with the bacteria. A number of chemical signals are sent between the plant and the bacterium that activates this symbiotic interaction. We know the nature of the chemical signal produced by the bacteria that induces this interaction. Our research will identify how the bacterial signal in a legume species, Medicago trunculata, persuades the root cells to engage in the symbiotic relationship with these bacteria.