Endoplasmic reticulum acyltransferase with prokaryotic substrate preference contributes to triacylglycerol assembly in Chlamydomonas

Abstract

Understanding the unique features of triacylglycerol (TAG) metabolism in microalgae may be necessary to realize the full potential of these organisms for biofuel and biomaterial production. In the unicellular green alga a chloroplastic (prokaryotic) pathway has been proposed to play a major role in TAG precursor biosynthesis. However, as reported here, contains a chlorophyte-specific lysophosphatidic acid acyltransferase, CrLPAAT2, that localizes to endoplasmic reticulum (ER) membranes. Unlike canonical, ER-located LPAATs, CrLPAAT2 prefers palmitoyl-CoA over oleoyl-CoA as the acyl donor substrate. RNA-mediated suppression of CrLPAAT2 indicated that the enzyme is required for TAG accumulation under nitrogen deprivation. Our findings suggest that has a distinct glycerolipid assembly pathway that relies on CrLPAAT2 to generate prokaryotic-like TAG precursors in the ER.

Multiomics analysis reveals a distinct mechanism of oleaginousness in the emerging model alga Chromochloris zofingiensis

“…Lysophosphatidic acid acyltransferase (LPAAT) mediates the second acylation leading to the formation of phosphatidic acid (PA). C. zofingiensis contains three putative LPAAT isoforms: Cz16g02090, a homologue of C. reinhardtii chloroplastic LPAAT (LPAAT1) (Yamaoka et al ., ) , Cz04g14150, a homologue of C. reinhardtii ER LPAAT (LPAAT2) (Kim et al ., ) and Cz10g20070. The former two were greatly upregulated (~3.9‐ and 4.7‐fold, respectively), whereas the third gene showed just a slight upregulation (<2‐fold) upon ND (Figure b and Table S5).…”

The lipid biochemistry of eukaryotic algae

“…pathway by Chlamydomonas because it lacks thylakoid lipids with 18C acids at the sn-2 position [113,244,245]. But this has recently been challenged by the discovery of an ERlocated lysophosphatidate acyltransferase (LPAAT) with substrate preference of 16C rather than an 18:0 FA at its sn-2 position in C. reinhardtii [247]. In addition, a chloroplast pathway for TAG formation in C. reinhardtii was recently reported [248].…”

Plastidial and ER Triacylglycerol Biosynthesis in a Growth Phase-Dependent Manner in the Heterokont Nannochloropsis oceanica

“…Fan et al (2011) demonstrated that nitrogen starved Chlamydomonas cells accumulated significantly higher amount of C16 fatty acid moieties, which is accounted for up to 90% of the total TAG implied the substrate specificity of plastidial LPAAT toward C16:0 fatty acid moieties rather than ER-localized LPAAT (Fan et al, 2011). These studies have provided the crucial role of subcellular organelles in governing the TAG biogenesis and our results which depicted that C16:0-fatty acids were the predominant fatty acid composition compared to other fatty acids, thereby provoking the necessity to interrogate the role of subcellular compartments in governing lipogenesis in a growthphase dependent manner (Kim et al, 2018).…”