Arabidopsis dolichol kinase AtDOK1 is involved in flowering time control

Dolichols are a class of isoprenoids that consist of highly polymerized and unsaturated long-chain isoprenes. They play crucial roles in protein glycosylation including N-glycosylation, because the oligosaccharide is assembled on a lipid carrier, dolichyl diphosphate. Arabidopsis DOLICHOL KINASE 1, AtDOK1 (At3g45040), encodes a functional dolichol kinase that is involved in plant reproductive processes. The expression of AtDOK1 is limited to highly pluripotent cells although protein glycosylation is thought to be required ubiquitously in the entire plant body. In this study, we further explored AtDOK1 functions by creating leaky knockdown mutants of DOK1. We used a microRNA-mediated gene suppression technique because knockout of DOK1 causes lethality. The DOK1 knockdown mutants showed an early flowering phenotype without any remarkable growth defect in vegetative tissues. Indeed, AtDOK1 was highly expressed in emerging shoot apical meristems as well as inflorescence and floral meristems. A subcellular localization study of DOK1 revealed that DOK1 was localized at the endoplasmic reticulum. Our findings suggest that the endoplasmic reticulum-localized catalytically active DOK1 is highly expressed in the meristems and is involved in the control of flowering time, possibly by post-transcriptional regulation including protein glycosylation.