Tunicamycin-induced Endoplasmic Reticulum-Quality Control Pathway and Endoplasmic Reticulum-Associated Degradation Mechanism in the diatom Phaeodactylum tricornutum

Tunicamycin inhibits the first step of protein N-glycosylation modification. However, the physiological, transcriptomic, and N-glycomic effects of tunicamycin on important marine diatom Phaeodactylum tricornutum are still unknown. In this study, comprehensive approaches were used to study the effects. The results showed that cell growth and photosynthesis were significantly inhibited in P. tricornutum under the tunicamycin stress. The soluble protein content was significantly decreased, while the soluble sugar and neutral lipid were dramatically increased to orchestrate the balance of carbon and nitrogen metabolism. 0.3 µg m-1 tunicamycin could not complete inhibited the N-glycosylation of protein, but it resulted in the differentially expression of ERQC and ERAD related genes. The upregulation of genes involved in ERQC and the activation of anti-oxidases were speculated to alleviate the tunicamycin stress. The differentially expression of genes related to ERAD was suggested to degrade the unfolded and/or incorrect N-glycoproteins induced by tunicamycin. The identification of mannose-type and complex-type N-glycan structures enriched the N-glycan database of diatom P. tricornutum and provided important information for studying the function of N-glycosylation modification on proteins. All in all, the proposed working models of ERQC and ERAD will provide a solid foundation for further in-depth study the related mechanism and the diatom expression system. Overall design: Comparative gene expression profiling analysis of RNA-seq data for wild type and wild type under 0.3ug/ml tunicamycin