Proteomic profile of the nucellus of castor bean (Ricinus communis L.) seeds during development

In this study, we performed a proteomic analysis of nucellus from two developmental stages of Ricinus communis seeds by a GeLC-MS/MS approach, using of a high resolution orbitrap mass spectrometer, which resulted in the identification of a total of 766 proteins that were grouped into 553 protein groups. The distribution of the identified proteins in stages III and IV into different Gene Ontology categories was similar, with a remarkable abundance of proteins associated with the protein synthesis machinery of cells, as well as several classes of proteins involved in protein degradation, particularly of peptidases associated with programmed cell death. Consistent with the role of the nucellus in mediating nutrient transfer from maternal tissues to the endosperm and embryo, a significant proportion of the identified proteins are related to amino acid metabolism, but none of the identified proteins are known to have a role as storage proteins. Moreover for the first time, ricin isoforms were identified in tissues other than seed endosperm. Results are discussed in the context of the spatial and temporal distribution of the identified proteins within the nucellar cell layers.