Mapping the N-linked glycosites of rice (Oryza sativa L.) germinating embryos

Abstract

Germination is a key event in the angiosperm life cycle. N-glycosylation of proteins is one of the most common post-translational modifications, and has been recognized to be an important regulator of the proteome of the germinating embryo. Here, we report the first N-linked glycosites mapping of rice embryos during germination by using a hydrophilic interaction chromatography (HILIC) glycopeptides enrichment strategy associated with high accuracy mass spectrometry identification. A total of 242 glycosites from 191 unique proteins was discovered. Inspection of the motifs and sequence structures involved suggested that all the glycosites were concentrated within [NxS/T] motif, while 82.3% of them were in a coil structure. N-glycosylation preferentially occurred on proteins with glycoside hydrolase activities, which were significantly enriched in the starch and sucrose metabolism pathway, suggesting that N-glycosylation is involved in embryo germination by regulating carbohydrate metabolism. Notably, protein-protein interaction analysis revealed a network with several Brassinosteroids signaling proteins, including XIAO and other BR-responsive proteins, implying that glycosylation-mediated Brassinosteroids signaling may be a key mechanism regulating rice embryo germination. In summary, this study expanded our knowledge of protein glycosylation in rice, and provided novel insight into the PTM regulation in rice seed germination.

Human protein paucimannosylation: cues from the eukaryotic kingdoms

“…For example, a recent study reported a high abundance of PMGs (76.7% of the N ‐glycome) in ungerminated Oryza sativa seeds, which decreased dramatically to 36.1% after 48 h of germination (Horiuchi, Hirotsu, & Miyanishi, ). The PMGs were proposedly carried by vacuolar‐resident storage proteins utilised for growth and development during germination (Horiuchi et al ., ), and were further suggested to be synthesised and preserved in the rice germ until germination (Ying et al ., ). These findings suggest that GnT‐I, Hex and the other glyco‐enzymes facilitating PMP synthesis in plants (see Section II.1 a ) are active during seed development.…”

Advances on Post-translational Modifications Involved in Seed Germination

“…The mutant of Arabidopsis UGT74F2 , a glycosyltransferase, accumulates high levels of glycosylated nicotinate, and the mutant displayed decreased rates of seed germination, of which the germination drawback of the ugt74f2 mutant could be fully recovered by overexpressing UGT74F2 ( Li W. et al, 2015 ). Moreover, N-glycosylation mapping of rice embryos during germination has discovered 242 glycosites from 191 unique proteins, and these N-glycosylated proteins were enriched in starch and sucrose metabolism pathway, which were predicted to interact with several BR signaling proteins, implying that N-glycosylation is involved in carbohydrate metabolism and BR signaling to regulate seed germination ( Ying et al, 2017 ).…”

Sweet Modifications Modulate Plant Development

“…However, N-and O-glycosylation are the most abundant in plants. It is estimated that approximately 50% of all proteins are glycoproteins, of which the majority is N-glycosylated [47,48]. The presence or absence of N-and O-glycans on glycoproteins has been shown to influence a proteins' activity, stability and functionality to a large extent, and plays a critical role in cellular signaling, molecular trafficking, plant development and adaptation to biotic and abiotic stresses [7,49,50] (Figure 1).…”

“…Moreover, these mutations can also affect the germination stage [ 130 ] ( Figure 4 ). In germinating rice seeds, the number of N-linked glycosites equaled 242, distributed over 191 glycoproteins, highlighting the abundance and importance of (N-linked) glycosylation for the germinating seed [ 48 ]. Results of Horiuchi et al [ 243 ] indicate that the glycosylation pattern of ungerminated and germinated rice seeds changes.…”