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Biotechnol Lett (2014) 36:175180 DOI 10.1007/s10529-013-1332-1
ORIGINAL RESEARCH PAPER
Nutrient limitation in Auxenochlorella protothecoides induces qualitative changes of fatty acid and expressionof caleosin as a membrane protein associated with oil bodies
Buntora Pasaribu I-Ping Lin
Chii-Shiarng Chen Chi-Yu Lu Pei-Luen Jiang
Received: 7 July 2013 / Accepted: 13 August 2013 / Published online: 28 September 2013 Springer Science+Business Media Dordrecht 2013
Abstract Oil bodies formed in Auxenochlorella protothecoides induced during limited nutrition had a coating of caleosin. The total lipid content obtained from A. protothecoides in unstressed cultures (rst week) was *210 mg/g compared to the 231 mg/g obtained in the third week (nutrient limited) and 290 mg/g obtained in the fourth week (nutrient limited). The proportion of total saturated fatty acids increased from 28 to 46 %, whereas that of total polyunsaturated fatty acids decreased from 52 to 35 %. The expression levels of the 28 kDa caleosin protein in A. protothecoides rose to a maximum up to 4 weeks; immunolocalization studies showed that caleosin was predominantly associated with the membranes of oil bodies.
Keywords Auxenochlorella protothecoides
Caleosin Fatty acids Membrane protein of oil
bodies Oil body Polyunsaturated fatty acids
Introduction
Oil bodies are organelles mainly composed of triacylglycerols (TAGs) and sterol esters and are surrounded by phospholipids containing some embedded proteins such as oleosin, caleosin, and stereoleosin (Frandsen et al. 2001; Lin and Tzen 2004; Tzen 2012). Interestingly, another possible oil body protein, major lipid droplet protein, is also present in green microalgae (Nguyen et al. 2011; Peled et al. 2011). The oil body protein found in Chlorella cells belongs to the caleosin family (Lin et al. 2012). Caleosin is a class of calcium-binding proteins comprising the EF-hand that is similar to oleosin, which is an associated protein bound to oil bodies (Chen et al. 1999). Caleosin contains an N-terminal hydrophilic domain with a single Ca2?-binding EF hand, a central hydrophobic region, and a C-terminal hydrophilic domain (Chen et al. 1999) that is involved in signaling and the oil body assembly or mobilization depending on the phosphorylation status (Poxleitner et al. 2006).
Chlorella is a eukaryotic photosynthetic microalga that is widely distributed (oceans, fresh water and soil) (Wu et al. 2001). Dried Chlorella biomass is an attractive food source owing to its high...