Proteomic Comparison Between Leaves from a Red-Flesh Mutant and Its Wild-Type in Sweet Orange

The red-flesh mutant Hong Anliu sweet orange is of high nutritional value due to its lycopene accumulation. Our previous studies on this mutant fruits suggested that photosynthesis and oxidative stress could promote the formation of mutation trait. However, leaf rather than fruit is the major part for some important biological processes such as photosynthesis. In this study, we analyzed the proteomic alteration in leaves of the red-flesh mutant Hong Anliu vs. its wild type (WT). Ten differentially expressed proteins were identified, of which two were involved in photosynthesis, three in oxidative stress, two in defense, and three in metabolism. The high up-regulation of photosynthetic proteins proved the hypothesis that enhanced photosynthesis could provide and transport more substrates into mutant fruits for carotenoid biosynthesis. Similar to the previous results in fruits, anti-oxidative proteins were highly up-regulated in leaves, suggesting the whole plant of Hong Anliu suffered from enhanced oxidative stress. Proteins involved in defense and metabolism were also identified, and their possible roles in the mutation were discussed.