Blue Light Perception by Both Roots and Rhizobia Inhibits Nodule Formation in Lotus japonicus.
In many legumes, roots that are exposed to light do not form nodules. Here, we report that blue light inhibits nodulation in Lotus japonicus roots inoculated with Mesorhizobium loti. Using RNA interference, we suppressed the expression of the phototropin and cryptochrome genes in L. japonicus hairy roots. Under blue light, plants transformed with an empty vector did not develop nodules, whereas plants exhibiting suppressed expression of cry1 and cry2 genes formed nodules. We also measured rhizobial growth to investigate whether the inhibition of nodulation could be caused by a reduced population of rhizobia in response to light. Although red light had no effect on rhizobial growth, blue light had a strong inhibitory effect. Rhizobial growth under blue light was partially restored in signature-tagged mutagenesis (STM) strains in which LOV-HK/PAS- and photolyase-related genes were disrupted. Moreover, when Ljcry1A and Ljcry2B-silenced plants were inoculated with the STM strains, nodulation was additively increased. Our data show that blue light receptors in both the host plant and the symbiont have a profound effect on nodule development. The exact mechanism by which these photomorphogenetic responses function in the symbiosis needs further study, but they are clearly involved in optimizing legume nodulation.
1 United Graduate School of Agricultural Sciences, Kagoshima University, Korimoto, Kagoshima 890-0065, Japan.|2 Department of Agro-Environmental Sciences, Faculty of Agriculture, Saga University, Honjyo-machi, Saga, Saga 840-8502, Japan.
Aya
A
Shimomura
2 Department of Agro-Environmental Sciences, Faculty of Agriculture, Saga University, Honjyo-machi, Saga, Saga 840-8502, Japan.
Ayumi
A
Naka
2 Department of Agro-Environmental Sciences, Faculty of Agriculture, Saga University, Honjyo-machi, Saga, Saga 840-8502, Japan.
Nobuyuki
N
Miyazaki
2 Department of Agro-Environmental Sciences, Faculty of Agriculture, Saga University, Honjyo-machi, Saga, Saga 840-8502, Japan.
Sayaka
S
Moriuchi
1 United Graduate School of Agricultural Sciences, Kagoshima University, Korimoto, Kagoshima 890-0065, Japan.|2 Department of Agro-Environmental Sciences, Faculty of Agriculture, Saga University, Honjyo-machi, Saga, Saga 840-8502, Japan.
Susumu
S
Arima
3 Department of Environmental Life Sciences, Tohoku University, Katahira, Aoba-ku, Sendai 980-8577, Japan.
Shusei
S
Sato
4 Kazusa DNA Research Institute, Kazusa-kamatari, Kisarazu, Chiba 292-0818, Japan.
Hideki
H
Hirakawa
5 RIKEN Plant Science Center, Yokohama, Kanagawa 230-0045, Japan.
Makoto
M
Hayashi
6 Department of Molecular, Cell and Developmental Biology, University of California-Los Angeles, Los Angeles, CA 90095-1606, U.S.A.; and.
Maskit
M
Maymon
6 Department of Molecular, Cell and Developmental Biology, University of California-Los Angeles, Los Angeles, CA 90095-1606, U.S.A.; and.|7 Molecular Biology Institute, University of California-Los Angeles.
Ann M
AM
Hirsch
1 United Graduate School of Agricultural Sciences, Kagoshima University, Korimoto, Kagoshima 890-0065, Japan.|2 Department of Agro-Environmental Sciences, Faculty of Agriculture, Saga University, Honjyo-machi, Saga, Saga 840-8502, Japan.
Akihiro
A
Suzuki
D056931:Cryptochromes / Q000235:genetics; D008027:Light; D000070116:Lotus / Q000235:genetics / Q000382:microbiology / Q000502:physiology / Q000528:radiation effects*; D059128:Mesorhizobium / Q000502:physiology / Q000528:radiation effects*; D016296:Mutagenesis; D056949:Phototropins / Q000235:genetics; D010940:Plant Proteins / Q000235:genetics; D055170:Plant Root Nodulation / Q000528:radiation effects*; D018517:Plant Roots / Q000235:genetics / Q000382:microbiology / Q000502:physiology / Q000528:radiation effects; D034622:RNA Interference; D013559:Symbiosis / Q000528:radiation effects*
D056931:Cryptochromes; D056949:Phototropins; D010940:Plant Proteins