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Metabolic and transcriptional response to the induction of a heterologous poly-3-hydroxybutyrate pathway in Phaeodactylum tricornutum

ABSTRACT: The marine diatom Phaeodactylum tricornutum is an emerging host for metabolic engineering, but little is known about how introduced pathways are integrated into the existing metabolic framework of the host and how this influences trans- and native-gene expression. In this study we used episomal vectors to express the heterologous poly-3-hydroxybutyrate (PHB) pathway in diatoms, which produces precursors for polymeric bioplastics from acetyl coenzyme-A (AcCoA). By experimentally perturbing cultivation conditions, we gained insight into the regulation of the endogenous metabolism in transgenic lines under various environmental scenarios. Biosynthesis of PHB led to distinct shifts in the metabolome of the host, and further analysis revealed a condition-dependent relationship between endogenous and transgenic metabolic pathways. Under N-limitation, which induced a significant increase in neutral lipid content, both metabolic and transcriptomic data suggest that AcCoA was preferentially shunted into the endogenous metabolism over the transgenic PHB pathway. In contrast, supply of organic carbon in the form of glycerol supported both fatty acid and PHB biosynthesis, suggesting cross-talk between cytosolic and plastidial AcCoA precursors. This is the first study to investigate the transcriptomic and metabolomic response of diatom cell lines expressing a heterologous multi-gene pathway under different environmental conditions, providing useful insights for future engineering attempts for pathways based on the precursor AcCoA.

ORGANISM(S): Phaeodactylum tricornutum CCAP 1055/1

PROVIDER: GSE224880 | GEO | 2024/02/07

REPOSITORIES: GEO

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Project description:Background. Bacillus subtilis is a favorable host for the production of industrially relevant proteins because of its capacity of secreting proteins into the medium to high levels, its GRAS (Generally Recognized As Safe) status, its genetic accessibility and its capacity to grow in large fermentations. However, production of heterologous proteins still faces limitations. Results. This study aimed at the identification of bottlenecks in secretory protein production by analyzing the response of B. subtilis at the transcriptome level to overproduction of eight secretory proteins of endogenous and heterologous origin and with different subcellular or extracellular destination: secreted proteins (NprE and XynA of B. subtilis, Usp45 of Lactococcus lactis, TEM-1beta -lactamase of Escherichia coli), membrane proteins (LmrA of L. lactis and XylP of Lactobacillus pentosus) and lipoproteins (MntA and YcdH of B. subtilis). Responses specific for proteins with a common localization as well as more general stress responses were observed. The latter include upregulation of genes encoding intracellular stress proteins (groES/EL, CtsR regulated genes). Specific responses include upregulation of the liaIHGFSR operon under Usp45 and TEM-1 beta-lactamase overproduction; cssRS, htrA and htrB under all secreted proteins overproduction; sigW and SigW-regulated genes mainly under membrane proteins overproduction; and ykrL (encoding an HtpX homologue) specifically under membrane proteins overproduction. Conclusions. The results give better insights into B. subtilis responses to protein overproduction stress and provide potential targets for genetic engineering in order to further improve B. subtilis as a protein production host. Samples for transcriptome analyses were induced at the exponential-growth phase (OD600 = 0.7) with 0.1% subtilin (subtilin containing supernatant of subtilin producing B. subtilis strain ATCC 6633). Cells were harvested 30 min after induction. Three or four independent cultures of each strain (target strains and controls) were used, and cells were sampled for microarray experiment.

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Metabolic and transcriptional response to the induction of a heterologous poly-3-hydroxybutyrate pathway in Phaeodactylum tricornutum

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