Loss of Nucleotide Sugar Transporter (AtNST) gene function in the Golgi membranes impairs pollen development and embryo sac progression in Arabidopsis thaliana

Nucleotide Sugar Transporters (NSTs) are transmembrane proteins that are localised in the Golgi membranes and transport nucleotide sugars from the cytosol to the Golgi lumen. Transported nucleotide-sugars serve as donors in post-translational modification of proteins/ lipids, and donate sugar moiety to the growing carbohydrate chain on the nascent protein/lipid molecule, a reaction catalysed by the enzyme glycosyltransferase. Here we reported that a mutation in the Arabidopsis thaliana gene At3g11320 coding for NST protein causes defects in male gametophyte development, including collapsed, nonviable pollen. This mutation also caused impairment in the female gametophyte progression by arresting it at the functional megaspore (FM) stage. Further, the mutant phenotype, including silique size and seed set, was reverted when the cDNA of the AtNST gene was over-expressed in the mutant background. No abortive ovules were found in the siliques from the complemented plants. The results suggest that AtNST (At3g11320) gene might be responsible for maintaining and regulating transport of nucleotide-sugars from cytoplasm to the Golgi lumen for the glycosylation of essential proteins/carbohydrates/lipids etc., which are necessary for both male and female gametophyte development stages. This study shed further light on the role of such nucleotide sugar transporters in plant reproductive development processes, at least in Arabidopsis.