Abstract
It is generally suggested that abscisic acid (ABA) involves in acquisition of desiccation tolerance and dormancy in zygotic embryos. On the other hand, carrot somatic embryos do not synthesize ABA and thus show no desiccation tolerance. We succeeded to induce desiccation tolerance in torpedo-shaped carrot somatic embryos by ABA treatment (1x10-^5 M; 7 days). Generally, it is suggested that VP1/ABI3 factor is important on seed-specific ABA signal transduction. We cloned a homolog of ABI3 gene, C-ABI3, from carrot somatic embryos. The expression of C-ABI3 was detected specifically in developing seeds, somatic embryos and embryogenic cells by Northern blot analysis. These tissues acquire desiccation tolerance by endogenous or exogenous ABA. Here, we made the transgenic plants showing ectopic expression of C-ABI3 in mature leaves or non-embryogenic cells (NC). The expression of some embryo-specific ABA-inducible genes was detected in ABA-treated (1 x 10-^5 M or 1 x 10-^4 M; 8 h or 24 h) mature leaves or NC of the transgenic plants by Northern blot analysis. Furthermore, desiccation tolerance was observed on ABA-treated (1 x 10-^4 M; 14 days) transgenic NC. These all results induce a conclusion that C-ABI3 functions on acquisition of desiccation tolerance through the control of expression of some ABA-inducible genes not only in zygotic embryos but also in somatic embryos of carrot.
