Golgi-localized manganese transporter PML3 regulates Arabidopsis growth through modulating Golgi glycosylation and cell wall biosynthesis.

Golgi is a critical compartment for both the reutilization of the essential micronutrient manganese (Mn) and its detoxification. However, whether Mn plays a role in the Golgi remains to be demonstrated in plants. We characterized the function of PML3, a member of the Unknown Protein Family UPF0016, in Mn transport and the regulation of plant growth, Golgi glycosylation and cell wall biosynthesis in Arabidopsis. We also investigated the relationship of PML3 with NRAMP2, a trans-Golgi network localized Mn transporter. PML3-GFP is preferentially localized in the cis-Golgi. PML3 can transport Mn to rescue the hypersensitivity of yeast mutant Δpmr1 to excess Mn. Two mutant alleles of PML3 displayed reduced plant growth and impaired seed development under Mn deficient conditions. The pml3 mutants also showed impaired Golgi glycosylation and cell wall biosynthesis under Mn deficiency. Double mutations of PML3 and NRAMP2 showed improved plant growth compared to that of single mutants under Mn deficiency, implying that PML3 and NRAMP2 play opposite roles in the regulation of Golgi Mn levels. Our results suggest that PML3 mediates the Mn uptake into the Golgi compartments, which is required for proper protein glycosylation and cell wall biosynthesis under Mn deficient conditions.