VR-ACS6 is an Auxin-Inducible l-Aminocyclopropane-l-carboxylate Synthase Gene in Mungbean (Vigna radiata)

We have isolated four cDNA clones of ACC synthase from etiolatedmungbean seedlings treated with auxin. PVR-ACS2, pVR-ACS3 andpVR-ACS6 contained the same sequences as the previously reportedDNA fragments, pMAC2, pMAC3 (Botella et al. 1992b) and pMBAl(Kim et al. 1992), respectively. pVR-ACSl was identical withpAIM-1 (Botella et al. 1992a). VR-ACS6 was specifically induced in response to the auxin signal.The IAA-induction of VR-ACS6 was very rapid (within 30 min)and insensitive to cycloheximide treatment at concentrationsup to 100 µM. Significant accumulation of VR-ACS6 mRNAwas detected at 1 µM.IAA.The IAA-induced expression ofVR-ACS6 was suppressed by ABA and ethylene, but enhanced byBA. These characteristics of VR-ACS6 expression were well correlatedwith the physiological data of auxin-induced ethylene productionin mungbean hypocotyls. VR-ACS1 was strongly induced by cycloheximide, but was foundto be not auxin-specific. Inhibitors of either ethylene biosynthesis(AOA) or action (NBD) increased the basal level of VR-ACS1 mRNA. (Received May 7, 1996; Accepted November 25, 1996)