ANALYSIS OF CITRUS SINENSIS L. (OSBECK) FLESH PROTEOME AT MATURITY TIME

A combination of 2-DE and LC-MSMS approaches was used to identify the differentially expressed proteome of 'Moro' blood sweet orange [Citrus sinensis (L.) Osbeck] in comparison with a common cultivar ('Cadenera') at ripening time. The comparison of the protein patterns of 'Moro' and 'Cadenera' showed 64 differential expressed protein spots. Fifty-five differentially expressed proteins were identified. Proteins were classified according to their putative function and known biosynthetic pathways. Most of the protein related to sugar metabolism were over-expressed in Moro, while those related to stress responses were over-expressed in 'Cadenera'. The abundance of proteins belonging to Unknown/Unnamed and Hypothetical classes could be associated to the incomplete data available on the Citrus genome. The relative abundance of Secondary metabolism and Oxidative process proteins substantiated the key role of the anthocyanin pathway in 'Moro', which is characterized by a strong pigmentation at ripening time. The potential role of proteins differentially expressed between 'Moro' and 'Cadenera' fruits was discussed, and proteomic results were compared with the known variations of transcripts on the same fruits. Discrepancies observed in our proteomic and transcriptomic analyses confirm the necessity to carry on further "omics" approaches to a better comprehension of our investigation. Moreover, the anthocyanins biosynthesis could be responsible in activating or repressing other related pathways, and this could justify the different expression of proteins not directly linked to the anthocyanins pathway in common and blood oranges.