We presume that this may be 1 of the techniques that B. subtilis makes use of in its struggle against other microorganisms in the mixed microbiological flora in the rhizosphere, the environmental situations of which B. subtilis perceives by way of the abundant flavonoids. A similar situation was observed for the habitat of Staphylococcus aureus, in which gene expression for the QacA major facilitator superfamily pump controlled by large-scale peptide synthesis, a member of the TetR household, is induced in response to the plant alkaloid berberine. LmrA and YxaF were the first characterized flavonoidresponsive regulators in the genus Bacillus.
On the other hand, NodD regulators, which belong to the LysR loved ones and manage transcription of the nod operons concerned in nodulation of Rhizobiales in response to flavonoid signals released by the leguminous hosts, have been characterized in detail. Also, in Pseudomonas putida DOT T1E, the resistance nodulationcell division family transporter TtgABC and the cognate TetR family members repressor TtgR constitute a multidrug recognition sys tem, and many flavonoids are substrates of TtgABC and trigger pump expression through binding to the TtgR operator complicated to dissociate it. Given that it is not unusual for flavonoids to function as signaling molecules for communication between soil bacteria and plants, it was anticipated that, in addition to the LmrA/YxaF regulon, B.
subtilis possesses genes concerned in flavonoid degradation or yet another physiological function for intercellular communication through flavonoids, which are beneath the control of unknown transcriptional regulators in response to flavonoids. In this research, in order to elucidate the complete regulatory program for the expression of the genes responsive PARP to flavonoids in B. subtilis, we attempted to determine additional genes that are considerably induced by flavonoid addition by indicates of DNA microarray assessment. Amid the new candidate flavonoid inducible genes located, we focused on the yetM gene encoding a putative flavin adenine dinucleotide dependent monooxygenase and on its transcriptional regulatory mechanism. DNA microarray examination involving the wild sort strain and a yetL disruptant, carried out in the framework of the Japan Functional Analysis Network for B.
BYL719 subtilis , advised that the item of the yetL gene, which encodes a putative transcriptional regulator of the MarR household and is situated immediately upstream of the yetM gene in the opposite route, negatively regulates yetM transcription, which is induced by particular flavonoids. DNA binding experiments involving recombinant YetL showed that small molecule library binds to the corresponding single websites in the yetL and yetM promoter areas, with particularly larger affinity for the latter area. The DNA binding of YetL was inhibited efficiently by flavonoids such as kaempferol, apigenin, and luteolin, and its weaker interaction with flavonoids this kind of as quercetin and fisetin appears to be diverse from the interaction of LmrA/YxaF.
To date, the flavonoid responsive transcriptional regulators of a number of microorganisms have cyclic peptide synthesis been reported. However, to our understanding, this is the 1st demonstration that a MarR household member particularly responds to flavonoids, which provides a clue for elucidation of the whole regulatory mechanism for flavonoid induced gene expression. The B. subtilis strains employed in this research are listed in Table 1. B. subtilis strain 168 was used as the standard strain. Strain YETLd was constructed by integration of plasmid pMUTIN2 into the yetL gene of strain 168.