The Golgi-localized transporter OsPML3 is involved in manganese homeostasis and complex N-glycan synthesis in rice

Manganese (Mn) is involved in many biochemical pathways as an enzyme cofactor, and is essential for maintaining metabolic processes in various plant cell compartments. Here, we determined the function of a rice (Oryza sativa) Mn transporter, PHOTOSYNTHESIS-AFFECTED MUTANT 71-LIKE 3 (OsPML3), belonging to the UNCHARACTERIZED PROTEIN FAMILY 0016 (UPF0016), in regulating Mn homeostasis and late-stage Golgi N-glycosylation. OsPML3 was highly expressed in rapidly developing tissues such as young leaves, root caps, lateral root primordia, and young anthers. Heterologous expression of OsPML3 restored the growth of Mn uptake-defective yeast strain Δsmf1 under Mn-limited conditions. Sub-cellular localization analysis revealed that OsPML3 localizes in the Golgi apparatus. At the vegetative stage, we observed necrotic root tips and lateral root primordia, and chlorotic young leaves in OsPML3 knockout lines under Mn-deficient conditions. Knocking out OsPML3 reduced the Mn content in the young leaves but did not affect the older leaves. Additionally, knocking out OsPML3 reduced the deposition of cell wall polysaccharides and the content of Lea (Lewis A structure)-containing N-glycan in roots and young leaves. OsPML3 knockout lines grown in the paddy field had reduced pollen fertility. Moreover, we found that the Lewis A structure was reduced in young anthers of OsPML3 knockout lines. Collectively, our results indicate that OsPML3 maintains Mn homeostasis in the Golgi apparatus of the rapidly developing rice tissues, and regulates the deposition of cell wall polysaccharides and late-stage Golgi N-glycosylation, especially biosynthesis of the Lewis A structure.