Overexpression of plastid lipid-associated protein in marine diatom enhances the xanthophyll synthesis and storage

Abstract

Plastoglobules, which are lipoprotein structures surrounded by a single hydrophobic phospholipid membrane, are subcellular organelles in plant chromoplasts and chloroplasts. They contain neutral lipids, tocopherols, quinones, chlorophyll metabolites, carotenoids and their derivatives. Proteomic studies indicated that plastoglobules are involved in carotenoid metabolism and storage. In this study, one of the plastid lipid-associated proteins (PAP), the major protein in plastoglobules, was selected and overexpressed in Phaeodactylum tricornutum. The diameter of the plastoglobules in mutants was decreased by a mean of 19.2% versus the wild-type, while the fucoxanthin level was increased by a mean of 51.2%. All mutants exhibited morphological differences from the wild-type, including a prominent increase in the transverse diameter. Moreover, the unsaturated fatty acid levels were increased in different mutants, including an 18.9–59.3% increase in eicosapentaenoic acid content. Transcriptomic analysis revealed that PAP expression and the morphological changes altered xanthophyll synthesis and storage, which affected the assembly of the fucoxanthin chlorophyll a/c-binding protein and expression of antenna proteins as well as reduced the non-photochemical quenching activity of diatom cells. Therefore, metabolic regulation at the suborganelle level can be achieved by modulating PAP expression. These findings provide a subcellular structural site and target for synthetic biology to modify pigment and lipid metabolism in microalgae chassis cells.

Proteomic characterization of a lutein-hyperaccumulating Chlamydomonas reinhardtii mutant reveals photoprotection-related factors as targets for increasing cellular carotenoid content

“…2 ). Recently, a plastoglobule-associated PAP-fibrillin protein was overexpressed in the diatom Phaeodactylum tricornutum , leading to a 51% increase in production of the carotenoid fucoxanthin [ 109 ]. Functionally characterizing PLAPs in C. reinhardtii could be worthwhile, as they could potentially act as a metabolic sink for carotenoids, preventing metabolite-induced feedback inhibition.…”

Towards Lipid from Microalgae: Products, Biosynthesis, and Genetic Engineering

“…As for the lipid synthesis, (i) by knockout of ∆9-DES, EPA accumulation was increased by 1.4-fold in P. tricornutum [122]; and (ii) overexpression of PtPAP exhibited smaller plastoglobule as well as increased fucoxanthin compared to the P. tricornutum wild-type. The PUFAs (including EPA) were also increased [123]; and (iii) coexpression of PtDGAT2B and a ∆5-FAE resulted in higher lipid yields and enhanced levels of DHA in TAG [124]. Finally, elevated carbon partition and lipid synthesis were combined by co-expression of a malic enzyme a∆5-DES in P. tricornutum.…”

Involvement of Transcription Factors and Regulatory Proteins in the Regulation of Carotenoid Accumulation in Plants and Algae

“…Overall, the association of these structural proteins with carotenoids in plastids is still largely unknown, especially in algae. Interestingly, overexpression of the PAP gene in the marine diatom Phaeodactylum tricornutum led to the accumulation of xanthophylls especially fucoxanthin in plastoglobules and the increase of unsaturated fatty acid levels . The manipulation of these structural proteins for carotenoid biofortification provides a new strategy for metabolic engineering and synthetic biology of carotenoids.…”