Identification of cDNA clones for tomato (Lycopersicon esculentum Mill.) mRNAs that accumulate during fruit ripening and leaf senescence in response to ethylene

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Abstract
Changes in gene expression during foliar senescence and fruit ripening in tomato (Lycopersicon esculentum Mill.) were examined using in-vitro translation of isolated RNA and hybridization against cDNA clones. During the period of chlorophyll loss in leaves, changes occurred in mRNA in-vitro translation products, with some being reduced in prevalence, whilst others increased. Some of the translation products which changed in abundance had similar molecular weights to those known to increase during tomato fruit ripening. By testing RNA from senescing leaves against a tomato fruit ripening-related cDNA library, seven cDNA clones were identified for mRNAs whose prevalence increased during both ripening and leaf senescence. Using dot hybridization, the pattern of expression of the mRNAs corresponding to the seven clones was examined. Maximal expression of the majority of the mRNAs coincided with the time of greatest ethylene production, in both leaves and fruit. Treatment of mature green leaves or unripe fruit with the ethylene antagonist silver thiosulphate prevented the onset of senescence or ripening, and the expression of five of the seven ripening- and senescence-related genes. The results indicate that senescence and ripening in tomato involve the expression of related genes, and that ethylene may be an important factor in controlling their expression.