Abstract
Rhizobium etli CE3 which is microsymbiont for Phaseolus vulgaris is reported to nodulate on Lotus japonicus. Nodules by R. etli, however, are early senescent thus unable to support full growth of the host symbiont. We hypothesized a gene(s) to support host growth that only exists in M. loti but not in R. etli and have initiated a project to clone it.
We are carrying out heterologous complementation using each clone of the ordered cosmid library of M. loti MAFF303099. Among examined half of the total 480 clones, there is no clone to complement, however, two M. loti genome regions conferred unexpected phenotypes of non-nodulation and extremely early senescence. The responsible genes situate, respectively, in 6.7 and 7.6 kbp regions that contain 7 and 11 ORFs with no similarity to known symbiotic genes. Possible roles of these novel genes in nodulation will be discussed.
