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Journal Article
- Identification and Functional Analysis of Acyl‑Acyl Carrier Protein Δ9 Desaturase from Nannochloropsis oceanica
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Ruigang Yang , Hui Wang , Lingyun Zhu , Lvyun Zhu , Tianzhong Liu , Dongyi Zhang
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J. Microbiol. 2023;61(1):95-107. Published online January 31, 2023
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DOI: https://doi.org/10.1007/s12275-022-00001-9
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Abstract
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The oleaginous marine microalga Nannochloropsis oceanica strain IMET1 has attracted increasing attention as a promising
photosynthetic cell factory due to its unique excellent capacity to accumulate large amounts of triacylglycerols and eicosapentaenoic
acid. To complete the genomic annotation for genes in the fatty acid biosynthesis pathway of N. oceanica, we
conducted the present study to identify a novel candidate gene encoding the archetypical chloroplast stromal acyl-acyl carrier
protein Δ9 desaturase. The full-length cDNA was generated using rapid-amplification of cDNA ends, and the structure of
the coding region interrupted by four introns was determined. The RT-qPCR results demonstrated the upregulated transcriptional
abundance of this gene under nitrogen starvation condition. Fluorescence localization studies using EGFP-fused
protein revealed that the translated protein was localized in chloroplast stroma. The catalytic activity of the translated protein
was characterized by inducible expression in Escherichia coli and a mutant yeast strain BY4389, indicating its potential
desaturated capacity for palmitoyl-ACP (C16:0-ACP) and stearoyl-ACP (C18:0-ACP). Further functional complementation
assay using BY4839 on plate demonstrated that the expressed enzyme restored the biosynthesis of oleic acid. These results
support the desaturated activity of the expressed protein in chloroplast stroma to fulfill the biosynthesis and accumulation
of monounsaturated fatty acids in N. oceanica strain IMET1.
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