Establishment of proteome spot profiles and comparative analysis of the red and green phenotypes of 'Bon Rouge' pear (pyrus communis L.) leaves

The 'Bon Rouge' pear (Pyrus communis L.) cultivar is characterized by high levels of anthocyanins, the pigments responsible for the red leaf and red fruit skin phenotype. Branches of 'Bon Rouge' pear trees planted in commercial orchards often revert to the original green phenotype. The study aimed at establishing proteome maps of 'Bon Rouge' pear leaves and at comparing the proteomes of the red and green phenotypes of these leaves. In this study, total proteins extracted from red and green leaves were resolved on two-dimensional (2D) polyacrylamide gel electrophoresis (PAGE) and stained with coomassie brilliant blue (CBB) to establish proteome maps. An average of 183 and 173 protein spots were detected in the red and green phenotypes, respectively. Using mass spectrometry, 12 differentially expressed proteins, as determined by the comparative PDQuest analysis of the two phenotypes, were positively identified. The identifications were then validated using the publicly available apple expressed sequence tag (EST) database. One of the proteins that was up regulated in the green phenotype was identified as phytochrome B, a protein involved with the inhibition of anthocyanin synthesis. Overall, the present data showed a predominant increase of photosynthesis-related proteins in the green leaves.