STRESS INDUCED DIFFERENTIAL GENE EXPRESSION PATTERNS FOR RED AND GREEN PHENOTYPES OF ‘BON ROUGE’ PEAR TREES (PYRUS COMMUNIS)

The ‘Bon Rouge’ pear (Pyrus communis, L.) under commercial production in the Western Cape region of South Africa is known to revert to its parent phenotype, ‘William’s Bon Chretien’, (‘Bartlett’). To investigate the underlying mechanism controlling the production of red pigment, anthocyanin, which is produced in response to a variety of stress conditions, we compared gene expression between red-leaved ‘Bon Rouge’ pear trees and their green sports. Differential display reverse transcription-polymerase chain reaction was used to detect differential gene expression between the two phenotypic variants with confirmation by quantitative RT-PCR. Several cDNA bands representing genes that are differentially regulated were cloned, sequenced and subjected to similarity searches on available database using the BLAST tool. Seven cDNA clones showed significant similarity to known genes including those associated with light stress, pathogenesis responses and protein synthesis. The pattern of altered gene expression observed between Bon Rouge and its reverted sport suggests this system presents an opportunity to identify a controlling element/gene for stress responses in the same genetic background.