Expression of genes for ethylene biosynthetic enzymes and an ethylene receptor in senescing flowers of miniature potted roses

Expression of genes for the ethylene biosynthetic enzymes ACC oxidase and A CC synthase, and the gene for a putative ethylene receptor, termed RhETR, i n miniature roses (Rosa hybrida) were examined during flower senescence of the long-lasting cv. Vanilla and cv. Bronze, which has a short flower life. The abundance of ACC oxidase transcript increased during the late stages o f flower development in petals of both cultivars, being higher for 'Bronze' than for 'Vanilla'. The ACC synthase transcript increased during flower se nescence in 'Vanilla' but remained constant at a low level in 'Bronze', The expression of RhETR was distinctly higher in the cultivar with short newer life ('Bronze') than in the long-lasting cultivar ('Vanilla'), and modulat ion of receptor levels was also observed during flower development. Exposur e to low ethylene concentrations resulted in an up-regulation of RhETR in f lowers of both cultivars, Differences in the expression of the putative eth ylene receptor of cultivars with short or long flower life suggest that var iation in flower longevity may be due to differences in receptor levels dur ing flower development.