N-glycan production in the endoplasmic reticulum of plants.

N-glycosylation is a complex process that encompasses the biosynthesis and modification of sugar moieties in the endoplasmic reticulum (ER) and Golgi. The ER-localized steps of N-glycan production in plants have received relatively little attention, despite their emerging roles in stress responses. Here, we integrate information on the molecular components underlying the three stages of N-glycan production: lipid-linked oligosaccharide synthesis, co-translational oligosaccharyl-transfer and quality control of the folded glycoprotein in the ER. The relative importance of each step for N-glycosylation and plant performance is evaluated on the basis of studies with inhibitors and mutant phenotypes. Finally, we highlight the increasing evidence for crosstalk between N-glycan production and defence responses in plants and discuss the practical implications for pathogen resistance.