Poster: Seed Biology

Abs # 544: Involvement of the transcriptional factors in the expression of abscisic acid-inducible genes during carrot somatic embryogenesis.

Presenter:	Shiota, Hajime , hshiota@yokohama-cu.ac.jp
Authors	Shiota, Hajime  (A)   Ko, Sukmin  (B)   Kamada, Hiroshi  (C)   Tanaka, Ichiro  (A)
Affiliations:	(A): Graduate School of Integrated Science, Yokohama City University (B): Plant Biotechnology, Department of Global Agricultural Sciences, The University of Tokyo (C): Institute of Biological Sciences, University of Tsukuba

Carrot somatic embryogenesis has been extensively used as an experimental system for studying embryogenesis. It is well known that abscisic acid (ABA) is involved in acquisition of desiccation tolerance and dormancy in zygotic embryos. On the other hand, somatic embryos contain low level of endogenous ABA and do not show desiccation tolerance, but the tolerance can be induced by exogenous application of ABA. It has been reported that the VP1/ABI3 factor functions as a transcriptional factor on seed specific ABA signal transduction. We had cloned and characterized a carrot homolog of the VP1/ABI3 factor, C-ABI3, and suggested that C-ABI3 is involved in acquisition of desiccation tolerance through the control of expression of some ABA-inducible genes (e.g. ECP genes) in carrot embryos. Recently, we isolated a cDNA clone of C-ABI3-like gene, C-ABI3L, from carrot somatic embryos. C-ABI3L showed high similarity to the VP1/ABI3 factors of some plant species at the four functional domains. The expression of C-ABI3L was observed in embryogenic cells, somatic embryos and developing seeds, but not in non-embryogenic cells, seedlings nor leaves. These results reveal that C-ABI3L is expressed in tissues and cells which acquire desiccation tolerance in response to endogenous or exogenous ABA, and indicate that C-ABI3L might function on ABA signal transduction in carrot embryos as well as C-ABI3. Furthermore, we cloned DcBZ1 gene encoding a GBF type bZIP protein from carrot somatic embryos. The recombinant protein of DcBZ1 produced by an Escherichia coli expression system showed binding activity to the ABA-responsive element (ABRE)-like motifs in the ECP31 promoter. The results suggest that DcBZ1 might be involved in ABA-induced expression of ECP31 in carrot embryogenesis.