| Fruit ripening and maturation are important not only for the plant, but for organisms that consume them. These processes are characterized by biochemical and physiological changes, with the fruit becoming more palatable. Fruits have been classically defined as being climacteric or non-climacteric, depending on the presence of a peak in respiration and ethylene production during ripening. Climacteric fruit ripening has been studied extensively, leading to increased knowledge of the regulation processes behind it. Non-climacteric fruits such as Citrus, however, have not yet been studied to this extent, and the knowledge is lacking in comparison. Proteomics is a powerful set of analytical techniques used to study the protein complement in a cell, tissue or organ that can lead to a better understanding of cellular processes. One advantage is that analysis of the proteins can give peptide sequences that can then be used to search for protein identities and functions, leading to identification of pathways that are regulated during physiological changes such as those occurring during fruit development. We used label-free proteomic methods to study the metabolic changes of two stages of Citrus fruit growth, 35mm fruit vs 55mm fruit and 55mm fruit vs 75 mm fruit. Our results showed that in the first comparison (35mm vs 55mm fruit), there was more regulation on proteins related to secondary metabolism (17%), followed by amino acid metabolism (14%), cell wall (11%), Major CHO (8%), redox (8%), among others. In the second comparison (55mm vs 75mm fruit), the metabolic assignment of proteins suggested shifts in metabolism, with glycolysis (16%) being the most represented, followed by cell wall (15%), secondary metabolism (13%), amino acid (10%), redox (10%), major CHO (9%), TCA cycle (9%), minor CHO (7%), photosynthesis (5%). |
