N-Glycoproteome Reveals That N-Glycosylation Plays Crucial Roles in Photosynthesis and Carbon Metabolism in Young Rice Leaves

Abstract

N-Glycosylation, one of the most prominent and abundant protein post-translational modifications in eukaryotic cells, is involved in diverse biological processes. To date, large-scale profiling of the N-glycoproteome has been only reported in rice germinating embryos, but that in rice leaves has not been profiled. Here, we report the first rice N-glycoproteome in leaves, determined by combining Concanavalin A (ConA) lectin affinity chromatography enrichment and high-resolution LC–MS/MS. In total, 282 N-glycopeptides, corresponding to 556 proteins and 643 sites, were identified from the leaves of H4 (indica) and LTH (japonica). Two conserved canonical N-glycosylation motifs N-X-T and N-X-S and two more non-canonical motifs N-X-S-X-N and A-X-X-N-X-S were revealed in rice. More than 50% of the identified proteins are localized to the chloroplast, extracellular part, and plasma membrane. Bioinformatics analysis revealed that N-glycosylation occurs on proteins involved in a wide variety of biological processes, especially photosynthesis and carbon metabolism. Protein–protein interaction networks of these proteins provided further evidence that N-glycosylation contributes to a wide range of regulatory functions. In summary, these findings revealed the complexity of the rice N-glycoproteome and provided useful information to further explore the regulatory roles of N-glycosylation in the growth, development, and stress responses of rice.