Heterogeneous expression of human PNPLA3 triggers algal lipid accumulation and lipid droplet enlargement

Microalgal metabolic engineering holds great promise for algal biofuels. However, identification of the key lipid metabolic target remains challenging due to its complex regulation. In this study, we advocated an alternative strategy that potentially rewired lipid metabolism by unprecedented mechanisms. PNPLA3, a human protein associated with non-alcoholic fatty liver disease (NAFLD), was firstly tested in microalgae for enhancing lipid accumulation. HsPNPLA3 was synthesized with a site mutation (I148M) and expressed in a model diatom Phaeodactylum tricornutum. Heterogeneous HsPNPLA3-I148M was successfully integrated, transcribed and expressed. Lipidomic analyses revealed that HsPNPLA3-I148M significantly elevated TAG content by 1.55-fold in algae, while algal growth and photosynthetic rate were not impaired. Fatty acid profile showed that content of C16:0, C18:1 and C20:4 was increased by 1.43-, 4.18- and 4.3-fold, respectively, which implied that HsPNPLA3-I148M might regulate the fatty acid substrate preference. Overall, the findings demonstrated that human PNPLA3 played a potential role in elevating TAG accumulation by regulating lipogenic enzymes and provide unprecedented insights into its functional significance.