TY - JOUR
T1 - Host plant genome overcomes the lack of a bacterial gene for symbiotic nitrogen fixation
AU - Hakoyama, Tsuneo
AU - Niimi, Kaori
AU - Watanabe, Hirokazu
AU - Tabata, Ryohei
AU - Matsubara, Junichi
AU - Sato, Shusei
AU - Nakamura, Yasukazu
AU - Tabata, Satoshi
AU - Jichun, Li
AU - Matsumoto, Tsuyoshi
AU - Tatsumi, Kazuyuki
AU - Nomura, Mika
AU - Tajima, Shigeyuki
AU - Ishizaka, Masumi
AU - Yano, Koji
AU - Imaizumi-Anraku, Haruko
AU - Kawaguchi, Masayoshi
AU - Kouchi, Hiroshi
AU - Suganuma, Norio
N1 - Funding Information:
Acknowledgements We thank E. Casalone and E. Dubois for providing Saccharomyces cerevisiae mutants; T. Bisseling for providing nitrogenase antibodies; Y. Kawaharada and H. Mitsui for technical help; and R. W. Ridge for critical reading of the manuscript. This work was supported by the Special Coordination Funds for Promoting Science and Technology of the Japanese Ministry of Education, Culture, Sports, Science and Technology.
PY - 2009/11/26
Y1 - 2009/11/26
N2 - Homocitrate is a component of the iron-molybdenum cofactor in nitrogenase, where nitrogen fixation occurs. NifV, which encodes homocitrate synthase (HCS), has been identified from various diazotrophs but is not present in most rhizobial species that perform efficient nitrogen fixation only in symbiotic association with legumes. Here we show that the FEN1 gene of a model legume, Lotus japonicus, overcomes the lack of NifV in rhizobia for symbiotic nitrogen fixation. A Fix-(non-fixing) plant mutant, fen1, forms morphologically normal but ineffective nodules. The causal gene, FEN1, was shown to encode HCS by its ability to complement a HCS-defective mutant of Saccharomyces cerevisiae. Homocitrate was present abundantly in wild-type nodules but was absent from ineffective fen1 nodules. Inoculation with Mesorhizobium loti carrying FEN1 or Azotobacter vinelandii NifV rescued the defect in nitrogen-fixing activity of the fen1 nodules. Exogenous supply of homocitrate also recovered the nitrogen-fixing activity of the fen1 nodules through de novo nitrogenase synthesis in the rhizobial bacteroids. These results indicate that homocitrate derived from the host plant cells is essential for the efficient and continuing synthesis of the nitrogenase system in endosymbionts, and thus provide a molecular basis for the complementary and indispensable partnership between legumes and rhizobia in symbiotic nitrogen fixation.
AB - Homocitrate is a component of the iron-molybdenum cofactor in nitrogenase, where nitrogen fixation occurs. NifV, which encodes homocitrate synthase (HCS), has been identified from various diazotrophs but is not present in most rhizobial species that perform efficient nitrogen fixation only in symbiotic association with legumes. Here we show that the FEN1 gene of a model legume, Lotus japonicus, overcomes the lack of NifV in rhizobia for symbiotic nitrogen fixation. A Fix-(non-fixing) plant mutant, fen1, forms morphologically normal but ineffective nodules. The causal gene, FEN1, was shown to encode HCS by its ability to complement a HCS-defective mutant of Saccharomyces cerevisiae. Homocitrate was present abundantly in wild-type nodules but was absent from ineffective fen1 nodules. Inoculation with Mesorhizobium loti carrying FEN1 or Azotobacter vinelandii NifV rescued the defect in nitrogen-fixing activity of the fen1 nodules. Exogenous supply of homocitrate also recovered the nitrogen-fixing activity of the fen1 nodules through de novo nitrogenase synthesis in the rhizobial bacteroids. These results indicate that homocitrate derived from the host plant cells is essential for the efficient and continuing synthesis of the nitrogenase system in endosymbionts, and thus provide a molecular basis for the complementary and indispensable partnership between legumes and rhizobia in symbiotic nitrogen fixation.
UR - http://www.scopus.com/inward/record.url?scp=70849100548&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=70849100548&partnerID=8YFLogxK
U2 - 10.1038/nature08594
DO - 10.1038/nature08594
M3 - Article
C2 - 19940927
AN - SCOPUS:70849100548
VL - 462
SP - 514
EP - 517
JO - Nature
JF - Nature
SN - 0028-0836
IS - 7272
ER -