DNA Research Advance Access published online on January 22, 2007
DNA Research, doi:10.1093/dnares/dsl017
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1 National Institute of Agrobiological Sciences, 2-1-2 Kannondai, Tsukuba, Ibaraki 305-8602, Japan; Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033, Japan; Bio-oriented Technology Research Advancement Institution (BRAIN), Tokyo Office, 3-18-19 Toranomon, Minato-ku, Tokyo 105-0001, Japan
* To whom correspondence should be addressed. Rhizobia-secreted Nod-factors (NFs) are required for nodulation. In the early developmental process of nodulation, a large number of changes occur in gene expression. Lotus japonicus nsp2 mutants isolated from Gifu B-129 ecotype have defects in nodule initiation and display non-nodulating phenotype. Here, we describe positional cloning of LjNSP2 as a component of the nodulation-specific signaling pathway. LjNSP2 was mapped near the translocation site of chromosome 1 where the recombination is severely suppressed. To circumvent this problem, we introduced Lotus burttii as an alternative crossing partner in place of L. japonicus Miyakojima. The development of the high-resolution map using a total of 11 481 F2 plants, in combination with newly developed DNA markers and construction of BAC library, enabled us to identify the gene responsible for mutant phenotype. LjNSP2 encodes a putative transcription factor of the GRAS family that constitutes a subfamily with Medicago truncatula NSP2. LjNSP2 was expressed in roots and early nodules, but strongly suppressed in matured nodules. The expression analysis of NIN and LjENOD40-1 genes in Ljnsp2 mutants indicates that LjNSP2 functions upstream of these genes. These results suggest that LjNSP2 acts as a transcription factor to directly or indirectly switch on the NF-induced genes required for nodule initiation. Communicated by Satoshi Tabata
Received November 30, 2006
Revised December 4, 2006
Full Papers
Positional Cloning Identifies Lotus japonicus NSP2, A Putative Transcription Factor of the GRAS Family, Required for NIN and ENOD40 Gene Expression in Nodule Initiation
Yasuhiro Murakami 1, Hiroki Miwa 2 
, Haruko Imaizumi-Anraku 3, Hiroshi Kouchi 4, J. Allan Downie 2, Masayoshi Kawaguchi 5 *, and Shinji Kawasaki 3
2 John Innes Centre, Colney Lane, Norwich NR4 7UH, UK
3 National Institute of Agrobiological Sciences, 2-1-2 Kannondai, Tsukuba, Ibaraki 305-8602, Japan; Bio-oriented Technology Research Advancement Institution (BRAIN), Tokyo Office, 3-18-19 Toranomon, Minato-ku, Tokyo 105-0001, Japan
4 National Institute of Agrobiological Sciences, 2-1-2 Kannondai, Tsukuba, Ibaraki 305-8602, Japan
5 Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033, Japan
Masayoshi Kawaguchi, E-mail: masayosi{at}biol.s.u-tokyo.ac.jp
Abstract Present address: Biotechnology Research Center, The University of Tokyo, 1-1-1 Yayoi, Bunkyo, Tokyo 113-8657, Japan
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