UP-REGULATION OF 2 RIPENING-RELATED GENES FROM A NONCLIMACTERIC PLANT(PEPPER) IN A TRANSGENIC CLIMACTERIC PLANT (TOMATO)

Activities of promoters from the capsanthin/capsorubin synthase and fi brillin genes, which are molecular markers for ripening in the non-cli macteric pepper fruits, have been studied in transgenic tomato plants that produce fruits of the climacteric type (characterized by an incre ase in respiration and ethylene production). The promoters of both gen es were strongly upregulated during tomato fruit ripening in a manner similar to the induction of these genes in pepper fruits. Induction oc curred at the mature green stage preceding ripening (a stage when ethy lene production and respiration are known to rise in tomato fruits). E thylene positively influenced the expression of both genes in tomato. Other plant growth regulators, namely abscisic acid, auxin and polyami nes, did not alter gene expression. In contrast, water loss strongly i nduced both promoters. This dehydration-mediated gene induction was in hibited by mitochondrial respiration inhibitors (mainly of the alterna tive oxidase). A slight positive effect with light, apparently not lin ked to normal photosynthesis but rather to photooxidative stress, was also observed. Taken together, the data indicate that activation of ox idase systems, leading to changes in the cellular redox balance, media tes the induction of both genes in tomato. Various cellular compartmen ts are likely to be contributors to this process, which leads to the d evelopmental regulation of nuclear genes encoding plastid-located prot eins.