AUTHOR=Ma Haiyan , Zheng Jie , Li Yanhua , Zhao Liang , Zou Song , Hu Qiang , Han Danxiang 

TITLE=A Novel Bifunctional Wax Ester Synthase Involved in Early Triacylglycerol Accumulation in Unicellular Green Microalga Haematococcus pluvialis Under High Light Stress

JOURNAL=Frontiers in Bioengineering and Biotechnology

VOLUME=9

YEAR=2022

URL=https://www.frontiersin.org/journals/bioengineering-and-biotechnology/articles/10.3389/fbioe.2021.794714

DOI=10.3389/fbioe.2021.794714

ISSN=2296-4185

ABSTRACT=<p>The bulk of neutral lipids, including astaxanthin esters and triacylglycerols (TAGs), are accumulated in the green microalga <italic>Haematococcus pluvialis</italic> under high light (HL) stress. In this study, a novel bifunctional wax ester synthase (WS) gene was cloned from <italic>H. pluvialis</italic> upon HL stress. The overexpression of HpWS restored the biosynthesis of wax esters and TAGs in neutral lipid-deficient yeast mutant <italic>Saccharomyces cerevisiae</italic> H1246 fed with C18 alcohol and C18:1/C18:3 fatty acids, respectively. Under HL stress, <italic>HpWS</italic> was substantially upregulated at the transcript level, prior to that of the type I diacylglycerol:acyl-CoA acyltransferase encoding gene (<italic>HpDGAT1</italic>). HpDGAT1 is the major TAG synthase in <italic>H. pluvialis</italic>. In addition, the application of xanthohumol (a DGAT1/2 inhibitor) in the <italic>H. pluvialis</italic> cells did not completely eliminate the TAG biosynthesis under HL stress at 24 h. These results indicated that HpWS may contribute to the accumulation of TAGs in <italic>H. pluvialis</italic> at the early stage under HL stress. In addition, the overexpression of HpWS in <italic>Chlamydomonas reinhardtii bkt5</italic>, which is engineered to produce free astaxanthin, enhanced the production of TAGs and astaxanthin. Our findings broaden the understanding of TAG biosynthesis in microalgae and provide a new molecular target for genetic manipulation in biotechnological applications.</p>