Arabidopsis, the most developed model plant for molecular genetics, belongs to the Brassicaceae, one of the rare families that do not form arbuscular mycorrhiza (AM). Therefore, another model plant was chosen to study the genetics of AM.
The perennial legume Lotus japonicus has a small genome size (400 Mb), a short generation time (3-4 months) and can be easily transformed using Agrobacterium-based protocols (Handberg and Stougaard 1992).
Resources have been established to facilitate map-based cloning of Lotus genes. Most mutagenesis experiments have been done with ecotype Gifu. The ecotype MG-20 is the most frequently used crossing parent to initiate mapping populations. Lotus burtii (Kawaguchi et al, 2005) and Lotus filicaulis are alternative crossing parents. Two mapping populations of recombinant inbred lines are available. An integrated genetic map of Lotus has been published (Hayashi et al. 2001).
Large datasets of Lotus ESTs are available in public databases (http://www.kazusa.or.jp/lotus/index.html). Large insert genomic libraries (BAC and TAC) of Lotus ecotypes Gifu and MG20 have been constructed.
Genome sequencing of the whole genome is in progress at the Kazusa DNA Research Institute (Cyranoski D 2001, http://www.kazusa.or.jp/lotus/index.html).
The laboratories of Trevor Wang at the John Innes Institute, and Martin Parniske at the Sainsbury Laboratory have established a TILLING reverse genetics tool for Lotus japonicus in close collaboration (Perry et al. 2003).
Masayoshi Kawaguchi, Andrea Pedrosa-Harand, Koji Yano, Makoto Hayashi, Yoshikatsu Murooka, Katsuharu Saito, Toshiyuki Nagata, Kiyoshi Namai, Hiroshi Nishida, Daisuke Shibata, Shusei Sato, Satoshi Tabata, Masaki Hayashi, Kyuya Harada, Niels Sandal, Jens Stougaard, Andreas Bachmair, and William F. Grant (2005) Lotus burttii Takes a Position of the Third Corner in the Lotus Molecular Genetics Triangle; DNA Res.; 12: 69 - 77.
Cyranoski D (2001) Japanese legume project may help to fix nitrogen problem. Nature, 409: 272
Handberg, K., and Stougaard, J. (1992). Lotus japonicus, an autogamous, diploid legume species for classical and molecular genetics. Plant Journal. 2:487-496.
Hayashi M, Miyahara A, Sato S, Kato T, Yoshikawa M, Taketa M, Hayashi M, Pedrosa A, Onda R, Imaizumi-Anraku, Bachmair A, Sandal N, Stougaard J, Murooka Y, Tabata S, Kawasaki S, Kawaguchi M and Harada K. (2001) Construction of a genetic linkage map of the model legume Lotus japonicus using an intraspecific F2 population. DNA Research 8:301-310.
Nakamura Y, Kaneko T, Asamizu E, Kato T, Sato S and Tabata S. (2002) Structural analysis of Lotus japonicus genome. II. Sequence features and mapping of sixty-five TAC clones which cover the 6.5 Mb regions of the genome. DNA Research 9:63-70.
Sato S, Kaneko T, Nakamura Y, Asamizu E, Kato T and Tabato S. (2001) Structural analysis of Lotus japonicus genome. I. Sequence features and mapping of fifty-six TAC clones which cover the 5.4 Mb regions of the genome. DNA Research 8:311-318.