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Title: EXPANSIN PROTEIN LEVELS DECLINE WITH THE DEVELOPMENT OF MEALINESS IN PEACHES

Author
item Obenland, David - Dave
item CRISOSTO, CARLOS - UNIV CA, KAC, PARLIER, CA
item ROSE, JOCELYN - CORNELL UNIV, ITHACA, NY

Submitted to: Postharvest Biology and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/30/2002
Publication Date: 7/1/2003
Citation: Obenland, D.M., Crisosto, C.H., Rose, J.K.C. Expansin protein levels decline with development of mealiness in peaches. Postharvest Biology and Technology. 2003. v. 29. p. 11-18.

Interpretive Summary: Peaches develop a dry flesh texture (mealiness) during cold storage that can render the fruit unmarketable. This disorder can be worsened as a result of certain quarantine treatments. We found that the protein expansin increases in amount during the ripening of peaches but the amount declines dramatically when peaches become mealy. Further research on the role that expansin plays in the development of peach mealiness may be useful in devising means to prevent its occurrence.

Technical Abstract: Expansin mRNA and protein expression in peaches was examined to investigate the possibility that expansins may be involved in the development of mealy flesh texture. Immunoblot analysis, using an expansin antibody, detected a 27-KDa protein corresponding to the predicted molecular mass of expansins in the later stages of ripening but not in full-size green fruit and indicated that expansin is associated with the progression of ripening in peaches. Peach cultivars `O'Henry' and `Summer Lady' were stored at 5C to induce the development of mealiness and individual fruit samples collected periodically to measure mealiness (free water) and provide samples for expansin quantification. Initially, stored fruit were juicy (50 to 60% free water), but as storage progressed, they became visibly mealy at free water percentages of 30% for `O'Henry' and 46% for `Summer Lady'. In both cultivars, expansin protein abundance decreased as the fruit became mealy. Development of mealiness within individual fruit was often not uniform and lead to the existence of distinct juicy and mealy regions. Immunoblot analysis indicated that mealy regions contained substantially less expansin than juicy regions. Analysis of expansin mRNA abundance using a ripening-related expansin cDNA probe from peach indicated that expansin mRNA expression was also markedly reduced in mealy tissues. The relationship observed in this study between expansin expression and mealiness suggests a possible role for expansin in the development of the disorder.