The researchers, funded by the Biotechnology and Biological Sciences Research Council (BBSRC), the Royal Society and the US National Science Foundation, have used a key gene that legumes require to establish the interaction with the nitrogen-fixing bacteria to trigger the growth of root nodules, even in the absence of the bacteria.
The fixation of nitrogen by some plants is critical to maintaining the health of soil as it converts the inert atmospheric form of nitrogen into compounds usable by plants. Legumes, as used in this study, are an important group of plants as they have the ability to fix nitrogen – which they owe to a symbiotic relationship with nitrogen-fixing bacteria in root nodules. Legumes are often used as a rotation crop to naturally enhance the nitrogen content of soils. Scientists have been working for a number of years to understand the symbiosis between legumes and rhizobial bacteria, with the hope that one day they can transfer this trait to crop plants, the majority of which cannot fix nitrogen themselves.
Intensive crop agriculture depends heavily on inorganic fertilisers that are often used to provide nutrients particularly nitrogen that are critical for plant growth. The production of nitrogen fertilisers requires a large amount of energy and is estimated to constitute approximately 50 per cent of the fossil fuel usage of the modern agricultural process. Inorganic fertilizers also cause environmental problems associated with leeching into our water systems.
Dr Giles Oldroyd is the research leader at JIC. He said: "We now have a good understanding of the processes required to activate nodule development. The nodule is an essential component of this nitrogen fixing interaction as it provides the conditions required for the bacteria. Nodules are normally only formed when the plant perceives the presence of the bacteria. The fact that we can induce the formation of nodules in the plant in the absence of the bacteria is an important first step in transferring this process to non-legumes. If this could be achieved we could dramatically reduce the need for inorganic nitrogen fertilizers, in turn reducing environmental pollution and energy use. However, we still have a lot of work before we can generate nodulation in non-legumes."
Professor Julia Goodfellow, Chief Executive of BBSRC, commented: "BBSRC is the principal funder of fundamental plant research in the UK and commits millions of pounds a year to furthering our understanding of basic plant biology. Such fundamental research may seem disconnected from the every day world for many people but this project shows how potentially important such science is. The findings have the potential to lead to a practical application with substantial economic impact for the UK."
The following images to accompany this story are available from the JIC and BBSRC Media Offices
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An ISDN studio is available for interviews at the John Innes Centre.
This research is published in Nature, June 29 2006, 'Nodulation independent of rhizobia induced by a calcium-activated kinase lacking autoinhibition'
This work was supported by the Biotechnology and Biological Sciences Research Council and the Royal Society. Research at Washington State University Agricultural Research Center was funded by the US National Science Foundation.
Medicago truncatula (Barrel Medic or Barrel Medick) is a small legume native to the Mediterranean region. It is a low-growing clover-like plant 10-60 cm tall with trifoliate leaves, each leaflet rounded, 1-2 cm long, often with a dark spot in the centre. The flowers are yellow, produced singly or in a small inflorescence of 2-5 together; the fruit is a small spiny pod.
M. truncatula has been chosen as a model organism for legume biology. It has a small diploid genome, is self-fertile, has a rapid generation time and prolific seed production, it is also amenable to genetic transformation.
The Biotechnology and Biological Sciences Research Council (BBSRC) is the UK's principal public funder of basic and strategic research across the biosciences. It is funded primarily by the Science Budget through the Government's Office of Science and Innovation. BBSRC invests over £350M pa in a wide range of research that makes a significant contribution to the quality of life for UK citizens and supports advances in the agriculture, food, chemical, healthcare and pharmaceutical sectors. www.bbsrc.ac.uk
About the John Innes Centre
The JIC, Norwich, UK is an independent, world-leading research centre in plant and microbial sciences with over 800 staff. JIC carries out high quality fundamental, strategic and applied research to understand how plants and microbes work at the molecular, cellular and genetic levels. The JIC also trains scientists and students, collaborates with many other research laboratories and communicates its science to end-users and the general public. The JIC is grant-aided by the Biotechnology and Biological Sciences Research Council. http://www.jic.ac.uk
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