Protein Disulfide Isomerase and Its Potential Function on Endoplasmic Reticulum Quality Control in Diatom Phaeodactylum tricornutum

PDI is a molecular chaperone and plays an important role in Endoplasmic Reticulum quality control (ERQC). PDI participates in the refolding of the misfolded/unfolded proteins to maintain cellular homeostasis under different stresses. However, bioinformatic characteristics and potential functions of PDIs in diatom Phaeodactylum tricornutum (Pt) are still unknown so far. Hence, the genome-wide characteristics of PtPDI proteins in P. tricornutum were first studied via bioinformatic and transcriptomic methods. 42 PtPDI genes were identified from the genome of P. tricornutum. The motif, protein structure, classification, number of introns, phylogenetic relationship, and the expression level of 42 PtPDI genes under the tunicamycin stress were analyzed. A pair of tandem duplicated genes (PtPDI15 and PtPDI18) was observed in P. tricornutum. The 42 PtPDIs with different gene characteristics were divided into three independent clades, indicating different evolutional relationships and functions of these PtPDIs. The 14 up-regulated PtPDI genes under the tunicamycin treatment might have a positive effect on the ER quality control of the unfolded/misfolded proteins, while the 7 down-regulated PtPDIs might negatively affect the ERQC. The characteristics of all 42 PtPDIs and their proposed working model here provide a comprehensive understanding of the PtPDIs gene family. The differential expression of 21 PtPDIs will be useful for further functional study in the ERQC.