Nutrient limitation in Auxenochlorella protothecoides induces qualitative changes of fatty acid and expression of caleosin as a membrane protein associated with oil bodies

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 (first 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.