Mediator subunit MED8 interacts with heat shock transcription factor HSF3 to promote fucoxanthin synthesis in the diatom Phaeodactylum tricornutum

• Published in: The New phytologist Vol. 241; no. 4; pp. 1574 - 1591
• Main Authors: Zhao, Hejing, Liu, Yan, Zhu, Zhengjiang, Feng, Qingkai, Ye, Yuemei, Zhang, Jinrong, Han, Jichang, Zhou, Chengxu, Xu, Jilin, Yan, Xiaojun, Li, Xiaohui
• Format: Journal Article
• Language: English
• Published: England Wiley Subscription Services, Inc 01.02.2024
• Subjects: Biosynthesis; Carotenoids; Chemical synthesis; Chromatin; Diabetes mellitus; Diatoms; Fucoxanthin; fucoxanthin synthesis; Gene expression; Genes; Genetic analysis; Genetics; Glyceraldehyde; Heat shock; Heat shock factors; HSF3; Immunoprecipitation; Localization; MED8; Mutants; Phaeodactylum tricornutum; Phenotypes; Phosphates; Proteins; Transcription; transcriptional regulation; MED8; Phaeodactylum tricornutum; HSF3; transcriptional regulation; fucoxanthin synthesis
• ISSN: 0028-646X; 1469-8137
• DOI: 10.1111/nph.19467

Summary Fucoxanthin, a natural carotenoid that has substantial pharmaceutical value due to its anticancer, antioxidant, antiobesity, and antidiabetic properties, is biosynthesized from glyceraldehyde‐3‐phosphate (G3P) via a series of enzymatic reactions. However, our understanding of the transcriptional mechanisms involved in fucoxanthin biosynthesis remains limited. Using reverse genetics, the med8 mutant was identified based on its phenotype of reduced fucoxanthin content, and the biological functions of MED8 in fucoxanthin synthesis were characterized using approaches such as gene expression, protein subcellular localization, protein–protein interaction and chromatin immunoprecipitation assay. Gene‐editing mutants of MED8 exhibited decreased fucoxanthin content as well as reduced expression levels of six key genes involved in fucoxanthin synthesis, namely DXS, PSY1, ZDS‐like, CRTISO5, ZEP1, and ZEP3, when compared to the wild‐type (WT) strain. Furthermore, we showed that MED8 interacts with HSF3, and genetic analysis revealed their shared involvement in the genetic pathway governing fucoxanthin synthesis. Additionally, HSF3 was required for MED8 association with the promoters of the six fucoxanthin synthesis genes. In conclusion, MED8 and HSF3 are involved in fucoxanthin synthesis by modulating the expression of the fucoxanthin synthesis genes. Our results increase the understanding of the molecular regulation mechanisms underlying fucoxanthin synthesis in the diatom P. tricornutum.