Transformation of a marker-free and vector-free antisense ACC oxidase gene cassette into melon via the pollen-tube pathway.

PURPOSE OF WORK: Melons have short shelf-lives due to fruit ripening caused by ethylene production. The 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase gene is essential for ethylene biosynthesis. As fruit ripening in other fruit crops can be deterred by down-regulation of ACC oxidase expression, we have carried out similar work to improve fruit quality and shelf-life of the melon Cucumis melo. A marker-free and vector-free antisense 1-aminocyclopropane-1-carboxylic acid oxidase construct was transformed into melon via the pollen-tube pathway. Based on phenotype analysis together with RT-PCR data, a transformation frequency of 0.7% was achieved. The transgenic fruits showed respiration rate and endogenous ethylene production level at approx. 15 and 6% of those of wild-type fruits, respectively. These fruits also demonstrated improved flesh firmness and exhibited extended shelf-life of 30 days compared to less than 12 days for the wild type fruits.