Two dimensional gel electrophoresis patterns of total, in vivo labelled and in vitro translated polypeptides from orange flavedo during maturation and following ethylene treatment

Abstract

Changes in the pattern of silver stained (SS), in vivo [35S]‐methionine labelled (IL), and in vitro poly(A+)RNA translated (IT) polypeptides from the flavedo of orange fruits [Citrus sinensis (L). Osbeck cv. Washington Navel] picked at three stages of maturity (mature‐green, turning and fully coloured) and treated with different doses of ethylene (0, 1 and 10 μl 1−1) were studied by two dimensional gel electrophoresis (using isoelectric focusing and nonequilibrium pH gradient as a first dimension). More than 500 SS, 300 IL, and 250 IT spots were detected in the gels. During maturation 32 SS, 2 IL and 2 IT spots decreased, whereas 2 SS, 3 IL and 2 IT spots increased. These results indicate that the maturation process is associated with a decrease of many accumulated flavedo proteins and with an increase of a reduced number of specific polypeptides, and that some of them may be regulated at the level of gene expression. All the spots which increased with maturity also increased with ethylene treatment, suggesting a role for this hormone in the maturation process. Ten IT spots which were not affected by maturity increased following ethylene treatment, while only 2 SS and 2 IL spots underwent this pattern of variation. Three spots recognized specifically by tobacco chitinase polyclonal antibodies remained essentially unaltered, whereas one spot whose intensity decreased significantly during maturation and ethylene treatment was identified as the large subunit of ribulose‐1,5‐bisphosphate carboxylase.