Abstract
Phytoplankton are primary producers in the marine ecosystem, where phosphorus is often a limiting factor of their growth. Hence, they have evolved strategies to recycle phosphorus by replacing membrane phospholipids with phosphorus-free lipids. However, mechanisms for replacement of lipid classes remain poorly understood. To improve our understanding, we performed the lipidomic and transcriptomic profiling analyses of an oleaginous marine microalga Nannochloropsis sp. PJ12 in response to phosphorus depletion (PD) and replenishing. In this study, by using (liquid chromatography couple with tandem mass spectrometry) LC-MS/MS-based lipidomic analysis, we show that membrane phospholipid levels are significantly reduced upon PD, while phosphorus-free betaine lipid levels are increased. However, levels of phosphorus-free photosynthetic galactolipid and sulfolipid are not increased upon PD, consistent with the reduced photosynthetic activity. RNA-seq-based transcriptomic analysis indicates that enzymes involved in phospholipid recycling and phosphorus-free lipid synthesis are upregulated, supporting the lipidomic analysis. Furthermore, enzymes involved in FASII (type II fatty acid synthesis) elongation cycle upon PD are transcriptionally downregulated. EPA (eicosapentaenoic acid) level decrease upon PD is revealed by both GC-MS (gas chromatography coupled with mass spectrometry) and LC-MS/MS-based lipidomic analyses. PD-induced alteration is reversed after phosphorus replenishing. Taken together, our results suggest that the alteration of lipid classes upon environmental change of phosphorus is a result of remodeling rather than de novo synthesis in Nannochloropsis sp. PJ12.
Highlights
Phytoplankton are primary producers that are believed to be responsible for nearly half of the global carbon-based photosynthesis [1,2]
Our results suggest that the alteration of lipid classes upon environmental change of phosphorus is a result of remodeling rather than de novo synthesis in Nannochloropsis sp
PJ12 cell were grown in flask containing f/2 medium [32] with orbital shaking at 100 rpm under continuous light of 50 μM photons m−1 s−1 at room temperature (25 ◦ C)
Summary
Phytoplankton are primary producers that are believed to be responsible for nearly half of the global carbon-based photosynthesis [1,2] Because of their relatively short generation time, they are very sensitive to the change of environmental stress conditions. Excess plastid membrane lipids are the potential pool for recycling phosphorus from PG and conversion into neutral lipid TAG (triacylglycerol) [9]. Non-plastid phosphorus-free betaine lipid DGTS (diacylglyceryltrimethylhomo-ser) is analogous to PC and PE [11], making it ideal for replacing PC and PE under phosphorus limited conditions. Upon phosphorus depletion, levels of unique thylakoid membrane-associated lipids DGDG, MGDG, PG, and SQDG and major non-plastid glycerophospholipids PC and PE are decreased, while level of non-plastid phosphorus-free betaine lipid DGTS, analogous to PC and PE, is increased. Transcriptional change of respective enzymes support the level change of the lipid classes
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
