Proteomics analysis of oil body-associated proteins in the oleaginous diatom

For biodiesel production from microalgae, it is desirable to understand the entire triacylglycerol (TAG) metabolism. TAG accumulation occurs in oil bodies, and although oil body-associated proteins could play important roles in TAG metabolism, only a few microalgal species have been studied by a comprehensive analysis. Diatoms are microalgae that are promising producers of biodiesel, on which such proteomics analysis has not been conducted to date. Herein, we identified oil body-associated proteins in the oleaginous diatom Fistulifera sp. strain JPCC DA0580. The oil body fraction was separated by cell disruption with beads beating and subsequent ultracentrifugation. Contaminating factors could be removed by comparing proteins from the oil body and the soluble fractions. This novel strategy successfully revealed 15 proteins as oil body-associated protein candidates. Among them, two proteins, which were parts of proteins predicted to have transmembrane domains, were indeed confirmed to specifically localize to the oil bodies in this strain by observation of GFP fusion proteins. One (predicted to be a potassium channel) was also detected from the ER, suggesting that oil bodies might originate from the ER. By utilizing this novel subtraction method, we succeeded in identifying the oil body-associated proteins in the diatom for the first time.