Abstract
Carrot (Daucus carota) somatic embryogenesis has been extensively used as an experimental system to investigate the development of zygotic embryogenesis. In zygotic and somatic embryos, abscisic acid (ABA) is involved in acquisition of desiccation tolerance and dormancy, and the VP1/ABI3 factor functions as a transcriptional factor on seed specific ABA signal transduction. We isolated two carrot homologs of the VP1/ABI3 factor, C-ABI3-1 and C-ABI3-2. Each gene exhibited similar expression profile during somatic embryogenesis and seed development. In the transgenic carrot cells showing ectopic expression of C-ABI3-1 or C-ABI3-2, the expression of some seed specific ABA-inducible genes was successfully induced by ABA-treatment. On a trans-activation assay using Arabidopsis abi3-6 or carrot non-embryogenic cells, both C-ABI3-1 and C-ABI3-2 decreased the expression of C-ABI3-1. These suggest that C-ABI3-1 and C-ABI3-2 may function collaboratively on ABA signal transduction in carrot embryos.
