Proteome analysis of Citrus sinensis L. (Osbeck) flesh at ripening time

A combination of 2-DE and LC-MSMS approaches was used to identify the differentiallyexpressed proteome of a pigmented sweet orange (Citrus sinensis, cv. Moro) in comparisonwith a common cultivar (Cadenera) at ripening time. The comparison of the protein patternsof Moro and Cadenera showed 64 differential expressed protein spots. Fifty-fivedifferentially expressed proteins were identified. Proteins were classified according totheir putative function and known biosynthetic pathways. Most of the proteins related tosugar metabolism were overexpressed in Moro, while those related to stress responses wereoverexpressed in Cadenera. The abundance of proteins belonging to Unknown/Unnamedand Hypothetical classes could be associated to the incomplete data available on the Citrusgenome. The relative abundance of Secondary metabolism and Oxidative process proteinssubstantiated the key role of the anthocyanin pathway in Moro, which is characterized by astrong pigmentation at ripening time. The potential role of protein differential expressionbetween Moro and Cadenera fruits was discussed, and proteomic results were comparedwith the known variations of transcripts of the same fruits. The latter analyses highlightedmany discrepancies, confirming the necessity to associate both proteomic andtranscriptomic approaches in order to achieve a more complete characterization of the biological system.