Abstract
It is reported that the secretion of phenolics, such as protocatechuic acid (PCA), is essential for solubilizing apoplasmic Fe. Molecular pathways and genes in these strategies have already been characterized, while the molecular mechanisms of phenolics secretion for Fe solubilization have not been clarified and the phenolics efflux transporter has not been identified.
We have identified Cadmium (Cd)-accumulating rice mutants named phenolics efflux zero 1 (pez1), in which the amount of PCA in the xylem sap and the root exudates dramatically decreased. PEZ1 localized to the plasma membrane, and transported PCA in Xenopus oocytes, and the transcripts were localized in the steles. In the roots of pez1, Fe concentration increased, while the expression of Fe regulated transporter which mediates Fe transport was induced, suggesting that the defect in PEZ1 would increase apoplasmic Fe and reduce available Fe in the root.
These results demonstrate that PEZ1 secretes PCA for the utilization of the apoplasmic Fe in the steles. The identification of the PEZ1 will significantly improve our understanding of the Fe nutrition in rice.
