Comparative Proteomic Analysis of the Diatom Phaeodactylum tricornutum Reveals New Insights Into Intra- and Extra-Cellular Protein Contents of Its Oval, Fusiform, and Triradiate Morphotypes

Comparative RNA-Seq of Ten Phaeodactylum tricornutum Accessions: Unravelling Criteria for Robust Strain Selection from a Bioproduction Point of View

The production of biologics in mammalian cells is hindered by some limitations including high production costs, prompting the exploration of other alternative expression systems that are cheaper and sustainable like microalgae. Successful productions of biologics such as monoclonal antibodies have already been demonstrated in the diatom Phaeodactylum tricornutum; however, limited production yields still remain compared to mammalian cells. Therefore, efforts are needed to make this microalga more competitive as a cell biofactory. Among the seventeen reported accessions of P. tricornutum, ten have been mainly studied so far. Among them, some have already been used to produce high-value-added molecules such as biologics. The use of "omics" is increasingly being described as useful for the improvement of both upstream and downstream steps in bioprocesses using mammalian cells. Therefore, in this context, we performed an RNA-Seq analysis of the ten most used P. tricornutum accessions (Pt1 to Pt10) and deciphered the differential gene expression in pathways that could affect bioproduction of biologics in P. tricornutum. Our results highlighted the benefits of certain accessions such as Pt9 or Pt4 for the production of biologics. Indeed, these accessions seem to be more advantageous. Moreover, these results contribute to a better understanding of the molecular and cellular biology of P. tricornutum.

Bioengineering of the Marine Diatom Phaeodactylum tricornutum with Cannabis Genes Enables the Production of the Cannabinoid Precursor, Olivetolic Acid

The increasing demand for novel natural compounds has prompted the exploration of innovative approaches in bioengineering. This study investigates the bioengineering potential of the marine diatom Phaeodactylum tricornutum through the introduction of cannabis genes, specifically, tetraketide synthase (TKS), and olivetolic acid cyclase (OAC), for the production of the cannabinoid precursor, olivetolic acid (OA). P. tricornutum is a promising biotechnological platform due to its fast growth rate, amenability to genetic manipulation, and ability to produce valuable compounds. Through genetic engineering techniques, we successfully integrated the cannabis genes TKS and OAC into the diatom. P. tricornutum transconjugants expressing these genes showed the production of the recombinant TKS and OAC enzymes, detected via Western blot analysis, and the production of cannabinoids precursor (OA) detected using the HPLC/UV spectrum when compared to the wild-type strain. Quantitative analysis revealed significant olivetolic acid accumulation (0.6-2.6 mg/L), demonstrating the successful integration and functionality of the heterologous genes. Furthermore, the introduction of TKS and OAC genes led to the synthesis of novel molecules, potentially expanding the repertoire of bioactive compounds accessible through diatom-based biotechnology. This study demonstrates the successful bioengineering of P. tricornutum with cannabis genes, enabling the production of OA as a precursor for cannabinoid production and the synthesis of novel molecules with potential pharmaceutical applications.

Quantitative proteomic analyses reveal the impact of nitrogen starvation on the proteome of the model diatom Phaeodactylum tricornutum

Diatoms are one of the largest groups in phytoplankton biodiversity. Understanding their response to nitrogen variations, present from micromolar to near-zero levels in oceans and fresh waters, is essential to comprehend their ecological success. Nitrogen starvation is used in biotechnological processes, to trigger the remodeling of carbon metabolism in the direction of fatty acids and triacylglycerol synthesis. We evaluated whole proteome changes in Phaeodactylum tricornutum after 7 days of cultivation with 5.5-mM nitrate (+N) or without any nitrogen source (-N). On a total of 3768 proteins detected in biological replicates, our analysis pointed to 384 differentially abundant proteins (DAP). Analysis of proteins of lower abundance in -N revealed an arrest of amino acid and protein syntheses, a remodeling of nitrogen metabolism, and a decrease of the proteasome abundance suggesting a decline in unselective whole-proteome decay. Analysis of proteins of higher abundance revealed the setting up of a general nitrogen scavenging system dependent on deaminases. The increase of a plastid palmitoyl-ACP desaturase appeared as a hallmark of carbon metabolism rewiring in the direction of fatty acid and triacylglycerol synthesis. This dataset is also valuable to select gene candidates for improved biotechnological properties.