Uri Pick - How are triacylglycerides produced in the green alga Dunaliella tertiolecta?

June 2016

  • Datum: 01.06.2016
  • Uhrzeit: 14:00 - 15:30
  • Vortragende(r): Uri Pick
  • Ort: Central Building
  • Raum: Seminar Room
  • Gastgeber: Omri Avidan
Green microalgae accumulate under stress conditions such as nitrogen limitation either starch or triacylglycerides (TAG) or both. The biosynthesis of TAG is of special interest because it is a potential source for production of biodiesel. However, there are still large gaps in our understanding about the enzymatic pathways of TAG biosynthesis and how it is controlled. This work was designed to clarify two issues in triacylglyceride (TAG) biosynthesis in green algae: what is the major rate-limiting stage in TAG biosynthesis and how much fatty acids (FA) that are channeled for TAG biosynthesis are produced de novo, from pre-formed polar lipids (PL) or from degradation of starch. The work was performed in the halotolerant alga Dunaliella tertiolecta by pulse labeling with 14C-palmitic acid (PA) and with 14C-bicarbonate. The results show that: (i) FA biosynthesis is the rate-limiting stage in TAG biosynthesis and it precedes the activation of glycerol transacylation into TAG, (ii) degradation of pre-formed lipids provides less than 10% of the FA in TAG, (iii) starch provides over 90% of the carbon for FA biosynthesis and as such is the major carbon source for FA and TAG biosynthesis under N deprivation, (iv) under control (+N) conditions, most FA are initially incorporated into phosphatidylcholine (PC). Under N deprivation incorporation into PC is inhibited, whereas incorporation into digalactosyldiacylglycerol (DGDG) is enhanced, suggesting that DGDG serves as an intermediate in acyl transfer into TAG. The significance of these results for our understanding of TAG biosynthesis and for future advances in improving TAG productivity in algae will be discussed.
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