Regulation of TG accumulation and lipid droplet morphology by the novel TLDP1 in Aurantiochytrium limacinum F26-b[S]

• Published in: Journal of lipid research 2017-12, Vol.58 (12), p.2334-2347
• Main Authors: Watanabe, Takashi, Sakiyama, Ryo, Iimi, Yuya, Sekine, Satomi, Abe, Eriko, Nomura, Kazuko H., Nomura, Kazuya, Ishibashi, Yohei, Okino, Nozomu, Hayashi, Masahiro, Ito, Makoto
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Cloning, Molecular; Deficient mutant; Escherichia coli - genetics; Escherichia coli - metabolism; Fatty Acids, Omega-3 - biosynthesis; Fatty Acids, Omega-3 - genetics; Gel electrophoresis; Gene Expression; Genetic Vectors - chemistry; Genetic Vectors - metabolism; Kinetics; lipid droplet protein; Lipid Droplets - chemistry; Lipid Droplets - metabolism; Morphology; Phylogeny; polyunsaturated fatty acid; Proteins; Recombinant Fusion Proteins - chemistry; Recombinant Fusion Proteins - genetics; Recombinant Fusion Proteins - metabolism; Sequence Alignment; Sequence Homology, Amino Acid; Stramenopiles - classification; Stramenopiles - genetics; Stramenopiles - metabolism; Substrate Specificity; thraustochytrid-specific lipid droplet protein 1; triacylglycerol; Triglycerides - biosynthesis; Triglycerides - genetics
• ISSN: 0022-2275; 1539-7262
• DOI: 10.1194/jlr.M079897

Thraustochytrids are marine single-cell protists that produce large amounts of PUFAs, such as DHA. They accumulate PUFAs in lipid droplets (LDs), mainly as constituent(s) of triacylglycerol (TG). We identified a novel protein in the LD fraction of Aurantiochytrium limacinum F26-b using 2D-difference gel electrophoresis. The protein clustered with orthologs of thraustochytrids; however, the cluster was evolutionally different from known PAT family proteins or plant LD protein; thus, we named it thraustochytrid-specific LD protein 1 (TLDP1). TLDP1 surrounded LDs when expressed as a GFP-tagged form. Disruption of the tldp1 gene decreased the content of TG and number of LDs per cell; however, irregular and unusually large LDs were generated in tldp1-deficient mutants. Although the level of TG synthesis was unchanged by the disruption of tldp1, the level of TG degradation was higher in tldp1-deficient mutants than in the WT. These phenotypic abnormalities in tldp1-deficient mutants were restored by the expression of tldp1. These results indicate that TLDP1 is a thraustochytrid-specific LD protein and regulates the TG accumulation and LD morphology in A. limacinum F26-b.