Phospholipid: diacylglycerol acyltransferase contributes to the conversion of membrane lipids into triacylglycerol in Myrmecia incisa during the nitrogen starvation stress

Abstract

In addition to the Kennedy pathway for de novo biosynthesis, triacylglycerol (TAG), the most important stock for microalgae-based biodiesel production, can be synthesized by phospholipid: diacylglycerol acyltransferase (PDAT) that transfers an acyl group from phospholipids (PLs) to diacylglycerol (DAG). This study presents a novel gene that encodes PDAT from the green microalga Myrmecia incisa Reisigl H4301 (designated MiPDAT ). MiPDAT is localized on the plasma membrane (PM) via the agroinfiltration of tobacco leaves with a green fluorescent protein-fused construct. MiPDAT synthesizes TAG based on functional complementary experiments in the mutant yeast strain H1246 and the membrane lipid phosphatidylcholine (PC) is preferentially used as substrates as revealed by in vitro enzyme activity assay. The gradually increased transcription levels of MiPDAT in M. incisa during the cultivation under nitrogen starvation conditions is proposed to be responsible for the decrease and increase of the PC and TAG levels, respectively, as detected by liquid chromatography-mass spectrometry after 4 d of nitrogen starvation. In addition, the mechanism by which MiPDAT in this microalga uses PC to yield TAG is discussed. Accordingly, it is concluded that this PM-located PDAT contributes to the conversion of membrane lipids into TAG in M. incisa during the nitrogen starvation stress.

The Microalga Nannochloropsis during Transition from Quiescence to Autotrophy in Response to Nitrogen Availability

“…9). In Chlamydomonas and other microalgae like Myrmecia incisa, the increase in PDAT transcript abundance under N deprivation reflected both the reduction in membrane phospholipid content and increased TAG accumulation (Yoon et al, 2012;Liu et al, 2016b). The involvement of PDAT in membrane recycling was also directly confirmed in Chlamydomonas, where a knockdown of PDAT resulted in the increase of membrane lipid content and decreased levels of TAG (Yoon et al, 2012), although in this case the enzyme uses lipids other than phosphatidylglycerol, which is absent in Chlamydomonas.…”

Characterization of Phospholipid: Diacylglycerol Acyltransferases (PDATs) from Camelina sativa and Their Roles in Stress Responses

“…Moreover, it has been reported that some PDATs located on the plasma membrane (e.g. MiPDAT, and RcPDAT2) ( Liu et al, 2016 ; Pan et al, 2015 ), while others are located in chloroplasts (e.g. CrPDAT) ( Yoon et al, 2012 ).…”

“…Compared with DGATs, relatively little functional information is available on PDATs ( Pan et al, 2015 ), although PDATs have been identified from yeast ( Saccharomyces cerevisiae ; encoded by LOR1 gene; Dahlqvist et al, 2000 ), Arabidopsis (AtPDAT1 and AtPDAT2; Ståhl et al, 2004 ), flax ( Linum usitatissimum ) (LuPDAT1 and LuPDAT2; Pan et al, 2013 ), castor bean (Ricinus communis) (RcPDAT1 and RcPDAT2; Kim et al, 2011 ), two green microalga Chlamydomonas reinhardtii (CrPDAT; Yoon et al, 2012 ) and Myrmecia incise ( MiPDAT ; Liu et al, 2016 ). In Arabidopsis, PDAT1 was not a key contributor of TAG content in developing seeds ( Mhaske et al, 2005 ), but exhibited overlapping function with DGAT1 in TAG biosynthesis in seed and pollen grain development ( Zhang et al, 2009 ).…”

Properties and Biotechnological Applications of Acyl‐CoA:diacylglycerol Acyltransferase and Phospholipid:diacylglycerol Acyltransferase from Terrestrial Plants and Microalgae

“…Considering medium chain fatty acids such as 12:0 are rarely incorporated into the sn-2 of PtdCho, which is the substrate of PDAT, it is likely that the relative use of PDAT and DGAT in TAG biosynthesis in leaves is dependent on the substrates and acyl flux conditions within the cell (Bates, 2016). Besides Arabidopsis, PDAT genes have also been identified and characterized in various plant and microalgal species, including castor (Kim et al, 2011;van Erp et al, 2011), flax (Pan et al, 2013), Camelina sativa (Aznar-Moreno and Yuan et al, 2017), green algae C. reinhardtii (Yoon et al, 2012), and green algae Myrmecia incise (Liu et al, 2016b). It should be noted that the PDAT nomenclature in the literature lacks consistency.…”

“…This is also supported by a recent detailed lipidomic analysis of developing B. napus seeds, in which the relative contributions of DGAT and PDAT were predicted based on the patterns of their molecular substrates (Woodfield et al, ). Furthermore, it has also been recently suggested that PDAT appears to function in stress responses in Arabidopsis (Mueller et al, ), C. sativa (Yuan et al, ), and green algae (Liu et al, ; Yoon et al, ). For instance, PDAT1‐mediated TAG accumulation was found to increase the heat resistance of Arabidopsis seedlings (Mueller et al, ).…”