Identification of a Chlamydomonas plastidial 2-lysophosphatidic acid acyltransferase and its use toengineer microalgae with increased oil content

Despite a strong interest in microalgal oil production, our understanding of the biosynthetic pathways that produce algal lipids and the genes involved in the biosynthetic processes remains incomplete. Here, we report that Chlamydomonas reinhardtii Cre09.g398289 encodes a plastid-targeted 2-lysophosphatidic acid acyltransferase (CrLPAAT1) that acylates the sn-2 position of a 2-lysophosphatidic acid to form phosphatidic acid, the first common precursor of membrane and storage lipids. In vitro enzyme assays showed that CrLPAAT1 prefers 16:0-CoA to 18:1-CoA as an acyl donor. Fluorescent protein-tagged CrLPAAT1 was localized to the plastid membrane in C.reinhardtii cells. Furthermore, expression of CrLPAAT1 in plastids led to a>20% increase in oil content under nitrogen-deficient conditions. Taken together, these results demonstrate that CrLPAAT1 is an authentic plastid-targeted LPAAT in C.reinhardtii, and that it may be used as a molecular tool to genetically increase oil content in microalgae.