Involvement of a novel genistein-inducible multidrug efflux pump of Bradyrhizobium japonicum early in the interaction with Glycine max (L.) Merr.
The early molecular dialogue between soybean and the bacterium Bradyrhizobium japonicum is crucial for triggering their symbiotic interaction. Here we found a single large genomic locus that is widely separated from the symbiosis island and was conspicuously induced within minutes after the addition of genistein. This locus (named BjG30) contains genes for the multidrug efflux pump, TetR family transcriptional regulator, and polyhydroxybutyrate (PHB) metabolism. The induction of BjG30 by genistein was competitively inhibited by daidzein, although both genistein and daidzein are soybean-derived inducers of nodulation (nod) genes. Such a differential expression pattern is also observed in some legume-derived flavonoids, which structurally differ in the hydroxy/deoxy group at the 5-position. In addition, not only did the induction start far in advance of nodW and nodD1 after the addition of genistein, but the levels showed distinct concentration dependence, indicating that the induction pattern of BjG30 is completely different from that of nod genes. The deletion of genes encoding either the multidrug efflux pump or PHB metabolism, especially the former, resulted in defective nodulation performance and nitrogen-fixing capability. Taken together, these results indicate that BjG30, and especially its multidrug efflux pump, may play a key role in the early stage of symbiosis by balancing the dual functions of genistein as both a nod gene inducer and toxicant.
Department of Agricultural and Life Sciences, Obihiro University of Agriculture and Veterinary Medicine.
Keisuke
K
Takeshima
Tatsuo
T
Hidaka
Min
M
Wei
Tadashi
T
Yokoyama
Kiwamu
K
Minamisawa
Hisayuki
H
Mitsui
Manabu
M
Itakura
Takakazu
T
Kaneko
Satoshi
S
Tabata
Kazuhiko
K
Saeki
Hirofumi
H
Oomori
Shigeyuki
S
Tajima
Toshiki
T
Uchiumi
Mikiko
M
Abe
Yoshihiko
Y
Tokuji
Takuji
T
Ohwada
D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D020369:Bradyrhizobium / Q000235:genetics / Q000502:physiology*; D015964:Gene Expression Regulation, Bacterial; D019833:Genistein / Q000378:metabolism*; D007529:Isoflavones / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000235:genetics* / Q000378:metabolism; D013025:Glycine max / Q000378:metabolism* / Q000382:microbiology*; D013559:Symbiosis
D001426:Bacterial Proteins; D007529:Isoflavones; D026901:Membrane Transport Proteins; C004742:daidzein; D019833:Genistein