Study on the ultrastructure and proteome of oil bodies in Brassica napus L.seeds

Rapeseed is one of the most important oil crops in China.The oil content of seeds is directly related to the national economy and people's livelihood.Fatty acids in rapeseeds are stored in the form of oil bodies composed of triacylglycerol (TAG) molecules,which are made of three fatty acid chains joined covalently to a glycerol molecule.We analyzed the ultrastructural characteristics of oil bodies in the seeds of four cultivars that contained varied oil content,including high oil content ‘ZS11’,medium oil content ‘Westar’ and ‘Topas’,and low oil content ‘ZS10’.Results showed that the size and density of the oil bodies in the four cultivars were varied.In the seeds of ‘ZS11’,the density of the oil bodies was higher but the size of the oil bodies was smaller (less than 1 μm in diameter).Interestingly,the density of the oil bodies in the seeds of the medium and low oil content cultivars was lower.Larger sized oil bodies were found in the seeds of the medium oil cultivars,but oil body size in the seeds of the low oil cultivar was diverse.Because oil-body protein composition is related to oil body size and oil content of seeds,total and oil-body protein profiles in the seeds of ‘ZS11’ and ‘Westar’ were explored by two-dimensional electrophoresis.Compared with the total protein profiles,57 differentially expressed proteins were detected in the seeds of both ‘Westar’ and ‘ZS11’ cultivars,indicating at least a two-fold difference in expression levels;in addition,24 and 23 proteins were specifically expressed in ‘Westar’ and ‘ZS11’ seeds,respectively.Compared with the oil-body protein profiles,we observed 52 differentially expressed proteins in the oil bodies of both cultivars,indicating at least a two-fold difference in expression levels;furthermore,we detected 2 and 13 proteins specifically expressed in oil-body proteins of ‘Westar’ and ‘ZS11’ seeds,respectively.Our findings indicate that the ultrastructure and protein composition of the oil bodies differed in different rapeseed cultivars.