Expression of ACCase subunit PtACC-1 from diatom Phaeodactylum tricornutum enhances neutral lipid production in Escherichia coli
Wei-Hong Xie, Fei Pang, Ying-Fang Niu, Meng-Han Zhang, Wei-Dong Yang, Jie-Sheng Liu , Dao-Guang Yan, Hong-Ye Li﹡

Key Laboratory of Functional Protein Research of Guangdong Higher Education Institutes, Jinan University, Guangzhou 510632.
﹡Corresponding Author： tel: +86-20-85228470; fax: +86-20-85222720; email: thyli@jnu.edu.cn

Abstract
Marine diatom Phaeodactylum tricornutum, a widely used forage species, contains storage lipid content up to 30% of dry cell weight. Acetyl-CoA carboxylase (ACCase) catalyzes the first committed step of fatty acid biosynthetic pathway. However, so far no study on ACCase from P. tricornutum has been reported. In this work, ACCase was identified from P. tricornutum by homologous searching. ACC-1 subunit of the ACCase (PtACC-1) was cloned and fused with a Myc epitope tag. PtACC-1-Myc was cloned into plasmid pMD18 driven by LacZ promoter and expressed heterologously in Escherichia coli. Expression of PtACC-1-Myc protein was verified by western blot. Neutral lipid content increased significantly by 1.36-fold determined by Nile red fluorescent dye staining. Fatty acid composition analyzed by GC-MS demonstrated a significant difference in the ratio of saturated fatty acid (SFA) and monounsaturated fatty acid (MUFA). MUFA of PtACC-1 expressing cells increased 28%. This study first characterized the key domains of ACCase from diatom and demonstrated a high neutral lipid accumulation in E. coli by expressing PtACC-1, also providing more genetic resource with potential for biodiesel development.

Key words:  ACCase; Lipid; Phaeodactylum tricornutum; Escherichia coli.