Protein composition of oil bodies from mature Brassica napus seeds

Abstract : Seed oil bodies (OBs) are intracellular particles storing lipids as food or biofuel reserves in oleaginous plants. Since Brassica napus OBs could be easily contaminated with protein bodies and/or myrosin cells, they must be purified step by step using floatation technique in order to remove non-specifically trapped proteins. An exhaustive description of the protein composition of rapeseed OBs from two double-zero varieties was achieved by a combination of proteomic and genomic tools. Genomic analysis led to the identification of sequences coding for major seed oil body proteins, including 19 oleosins, 5 steroleosins and 9 caleosins. Most of these proteins were also identified through proteomic analysis and displayed a high level of sequence conservation with their Arabidopsis thaliana counterparts. Two rapeseed oleosin orthologs appeared acetylated on their N-terminal alanine residue and both caleosins and steroleosins displayed a low level of phosphorylation.