N-glycosylation is involved in stomatal development partially by modulating the release of active abscisic acid and auxin by β-glucosidase in Arabidopsis thaliana

Asparagine-linked glycosylation (N-glycosylation) is one of the most important protein modifications in eukaryotes, affecting the folding, transport, and function of a wide range of proteins. However, it is still less known about the roles of N-glycosylation in the development of stomata in plants. In the present study, we provided evidence that the stt3a-2 mutant, defective in oligosaccharyltransferase (OST) catalytic subunit STT3, had a greater transpirational water loss and weaker drought avoidance, accompanied by aberrant stomatal distribution. Through physiological, biochemical, and genetic analyses, we found that the abnormal stomatal density of stt3a-2 was partially attributed to a low endogenous abscisic acid (ABA) and auxin (IAA) content. Exogenous application of ABA or IAA could partially rescue the mutant salt-sensitive and abnormal stomatal phenotype. Further analyses revealed that the decrease of IAA or ABA in stt3a-2 seedlings was associated with the under-glycosylation of β-glucosidase (AtBG1), catalyzing the conversion of conjugated ABA/IAA to active hormones. Our results provide strong evidence that N-glycosylation is involved in stomatal development and participates in abiotic stress tolerance by affecting the release of active plant hormones.

Keywords: N-glycosylation; abscisic acid; auxin; stomatal development; stress tolerance; β-glucosidase.