Abstract
Chengiopanax sciadophylloides is a Japanese tree known to accumulate large concentrations of Mn. The foliar Mn concentrations of mature trees were consistently found to exceed 10,000 mg kg-1 DW, with recorded maximum values of up to 23,500 mg kg-1. This phenomenon was recognized at non Mn-contaminated soil area, without showing other metal hyperaccumulations. To clarify the role of MnO2 solubilization for Mn acquisition and further hyperaccumulation, we examined the lowering of pH in the rhizosphere of this plant. The plants regenerated from C. sciadophylloides calli lowered the pH of the culture broth continuously and simultaneously solubilized MnO2 added to the medium, and rapidly increased the Mn content of the plant. We also isolated two prospective genes of C. sciadophylloides (CsZIP1 and CsNramp1), which were speculated to be Mn transporters, but their expressions did not rescue the Mn transport ability of yeast lacking the Mn transporter ability.
