STIMULATION AND INHIBITION OF EXPRESSION OF RIPENING-RELATED MESSENGER-RNAS IN TOMATOES AS INFLUENCED BY CHILLING TEMPERATURES

The effects of chilling temperatures on developmental gene expression in tomato fruit have been examined using eight ripening-related cDNA clones as hybridization probes. Fruit were harvested at the breaker stage of maturity and ripened at 24 °C, or held at 4 °C for 6, 12 or 18 days before being transferred to 24 °C. When fruit were held at 24 °C without chilling, they accumulated lycopene and produced ethylene in a typical pattern. At 4 °C both lycopene accumulation and ethylene production were inhibited. With increasing periods at chilling temperatures, subsequent ripening at 24 °C, as indicated by lycopene accumulation, was reduced. Ethylene production at 24 °C was relatively unaffected by previous chilling temperatures. The patterns of accumulation of mRNAs homologous to the cDNA clones at both 4 °C and after transfer to 24 °C were variable. At 4 °C, expression of most mRNAs declined steadily to low levels over 18 days. However, expression of mRNA homologous to pTOM 13, a clone thought to be associated with ethylene synthesis, was unique in that levels increased to a maximum after 9 days at 4 °C before declining. After transfer of fruit to 24 °C, accumulation of this mRNA declined rapidly and then increased, but only to levels of about 30 % of the maximum observed at 4 0C. Expression of the other mRNAs generally increased after transfer to 24 °C, but the timing of maximum expression was dependent on the chilling period and the clone concerned. The appearance of polygalacturonase mRNA at 24 °C was markedly reduced after 18 days at 4 °C. © 1990, Gustav Fischer Verlag, Stuttgart. All rights reserved.