P0013
Protein Composition of Lipid Droplet of Oleaginous Microalga Phaeodactylum tricornutum
Lipid droplet is a dynamic cytoplasmic organelle and contains the assembly of tria cyglycerides (TAGs) and proteins coated with a phospholipid monolayer. Lipid droplets (LD) play an important role in lipid storage and lipid metabolism.
Many species of microalgae can accumulate large amounts of TAGs under the scarcity of nutritions and have become the most potential raw material for renewable energy sources. TAGs are generally stored in intercellular lipid droplets which contain LD-associated proteins to maintain the structure and function of the organelle.
However, little is currently known at the cellular or molecular levels of lipid accumulation in microalgae, especially the constitutive and fuctional proteins which are involved in the synthesis, maintenance, and degradation of storage lipids.
To further study the microalgal lipid droplets, in this study we focused on the protein composition in a model diatom Phaeodactylum tricornutum. Totally 12 and 595 proteins were identified in lipid droplets-enriched fractions by using MALDI-MS and LC-MS, respectively. Two putative proteins designated LDPT-1 and LDPT-2 were choosen from these proteins for further characterization. Their transcript abundance increased significantly under nitrogen deprivation determined by qPCR. In the RNAi knockdown transgenic microalgae, expression of the two genes were repressed, and the lipid droplets showed remarkable changes. Under nitrogen deprivation, lipid accumulation and the morphology of lipid droplets showed significant changes. More lipid droplets and higher amount of lipids were detected. The results got an first insight to the protein composition of lipid droplets in diatoms and also providing more targets for improvement of microalgal biofuels.