Cu(II): a “signaling molecule” of the mangrove endophyte ZZF51?

We previously reported the isolation of Cu–fusaric acid (Cu–FA) complex from the mangrove endophyte ZZF51. In this study, we explored the mechanism of Cu–FA production in the strain ZZF51 by comparing with that of another endophyte sp. B2, which produced FA but not Cu–FA in the same culture condition. The results allowed us to hypothesize that Cu may act as a “signaling molecule” to awaken the silent FA biosynthetic genes in ZZF51, inducing intracellular production of FA followed by chelation with Cu. This signaling network was triggered specifically by Cu and may be interfered by other metal ions.