A tale of two sugars: O-GlcNAc and O-fucose orchestrate growth, development, and acclimation in plants

Post-translational modifications of nucleocytoplasmic proteins by O-linked beta-N-acetylglucosamine (O-GlcNAc) and O-linked fucose (O-fucose) are emerging as key signaling mechanisms in plants. O-fucosylation and O-GlcNAcylation are catalyzed by SPINDLY (SPY) and SECRET AGENT (SEC), respectively, which are redundantly essential for viability and growth yet function antagonistically or independently in specific developmental contexts. Proteomic studies have identified hundreds of O-GlcNAcylated and O-fucosylated nucleocytoplasmic proteins, revealing their regulatory roles and intersections with phosphorylation pathways that mediate nutrient and hormone signaling. Functional studies on O-glycosylated proteins demonstrate diverse impacts on protein activity and biological processes. Together, O-fucosylation, O-GlcNAcylation, and phosphorylation form a regulatory network that controls plant growth, development, and acclimation. This review highlights recent progress and outlines future directions in studying O-fucosylation and O-GlcNAcylation in plants.