CLONING OF A CDNA FOR A 1-AMINOCYCLOPROPANE-1-CARBOXYLATE SYNTHASE THAT IS EXPRESSED DURING DEVELOPMENT OF FEMALE FLOWERS AT THE APICES OF CUCUMIS-SATIVUS L

In cucumber (Cucumis sativus L.) plants, it has been reported that a h igh correlation existed between the evolution of ethylene from the api ces and the development of female flowers. We isolated three distinct cDNA encoding 1-aminocyclopropane-1-carboxylate (ACC) synthase from cu cumber, Among of these, only CS-ACS2, mRNA was detected at the apices of gynoecious cucumber in which female flowers were developing. The ex pression of the CS-ACS2 gene was examined in the apices of three cucum ber cultivars (Rensei, Ougonmegami 2-gou and Shimoshirazu) by RNA gel blot analysis. In these cultivars, both the timing and the levels of e xpression of the CS-ACS2 transcript were correlated with the developme nt of female flowers at the nodes. Furthermore, the timing of the indu ction of expression of the CS-ACS2 gene at the apex corresponded to th at of the action of ethylene in induction of the first female bower at the apex of gynoecious cucumber plants. These results suggest that th e development of female flowers might be regulated by the level of CS- ACS2 mRNA at the apex.