Scientists at the Shanghai Center for Plant Stress Biology, Center for Excellence in Molecular Plant Sciences of the Chinese Academy of Sciences (CAS), and South China Normal University discovered that cis-Golgi localized Mn transporter PML3 can pump Mn into Golgi to regulate Golgi glycosylation and cell wall biosynthesis in Arabidopsis thaliana under Mn deficiency.

The transition metal manganese (Mn) is an essential micronutrient for plants and acts as a cofactor or activator to be involved in the regulation of diverse biological processes. Transporters are essentially required for Mn uptake, remobilization and detoxification. Several Mn transporters have been showed to be localized to Golgi and required for Mn utilization and detoxification, indicating that Golgi is an important compartment for Mn storage. However, it is still unclear whether Mn plays a role in the Golgi in plants.

Chang-Hong Yang and colleagues in Chao-Feng Huang’s and Chengwei Yang’s labs demonstrate that Golgi Mn plays a critical role in protein glycosylation and associated cell wall biosynthesis through the functional characterization of a cis-Golgi-localized Mn transporter PML3, a member of the Unknown Protein Family UPF0016. PML3 functions in transporting Mn from cytoplasm to the Golgi and is essentially required for plant growth at later stages of plant development, especially at reproductive stages, under Mn deficient conditions. They found that protein glycosylation was deficient in pml3 mutants under Mn deficiency, which could be partially attributed to Mn deficiency-induced reduction of mannosidase activity. They further revealed that the impaired Golgi glycosylation reduces the protein level and stability of RSW2 regulating cellulose biosynthesis, which might partially causes the defective cell wall biosynthesis in the mutants under Mn deficient conditions. In addition, they discovered that PML3 and trans-Golgi network (TGN)-localized NRAMP2 coordinately regulate Golgi Mn levels and play different roles in the modulation of Mn utilization and plant growth in low Mn conditions. Their results suggest that the coordinated action of PML3 and NRAMP2 in the transport of Golgi Mn enables plants to utilize Mn efficiently in low Mn conditions.

Together, their results reveal the important role of PML3 in the regulation of Mn levels in the Golgi, which is crucial for Golgi glycosylation and cell wall biosynthesis under Mn deficient conditions.

Funding: This work was supported by the funding from the Shanghai Center for Plant Stress Biology, Chinese Academy of Sciences, the National Natural Science Foundation of China (Grant No. 31670286), and National Key Laboratory of Plant Molecular Genetics.

Link to this article:  https://nph.onlinelibrary.wiley.com/doi/10.1111/nph.17209