The pectin methylesterase OsPME14 modifies the cell wall to confer copper tolerance in Oryza sativa L.

Pectin methylesterase (PME) dynamically regulates the biomechanical properties of the cell wall, which is involved in plant development and resistance to biotic and abiotic stress. However, its regulation mechanism of plant tolerance to heavy metal toxicity is limited. Here, we functionally characterized a member of the PME family, OsPME14 in rice, which is required for Cu tolerance. The expression of OsPME14 was induced by Cu. Compared to WT, lost function of OsPME14 decreased the PME activity and carboxyl group content, and weakened the retention capacity of the cell wall to Cu, thereby enhancing the Cu absorption by roots and Cu accumulation in the protoplasts. This promoted the Cu translocation from roots to shoots, resulting in the Cu hypersensitivity phenotype and more Cu concentration in grains. Notably, mutation of OsPME14 caused the expression change of the receptor kinase gene and the downstream MAPK cascade pathway. Besides, a PME inhibitor OsPMEI6 was identified to interact with OsPME14, and the spatiotemporal expression of OsPMEI6 was highly consistent with OsPME14, OsPMEI6 may regulate OsPME14-mediated Cu tolerance in rice. These results provide a novel insight into OsPME14-OsPMEI6 module-mediated mechanisms of heavy metal tolerance in rice.