Identification and characterization of bZIP-type transcription factors involved in carrot (Daucus carota L.) somatic embryogenesis
Article first published online: 16 JUL 2009
© 2009 The Authors. Journal compilation © 2009 Blackwell Publishing Ltd
The Plant Journal
Volume 60, Issue 2, pages 207–217, October 2009
How to Cite
Guan, Y., Ren, H., Xie, H., Ma, Z. and Chen, F. (2009), Identification and characterization of bZIP-type transcription factors involved in carrot (Daucus carota L.) somatic embryogenesis. The Plant Journal, 60: 207–217. doi: 10.1111/j.1365-313X.2009.03948.x
- Issue published online: 8 OCT 2009
- Article first published online: 16 JUL 2009
- Received 16 February 2009; revised 30 April 2009; accepted 2 June 2009; published online 16 July 2009.
- bZIP-type transcription factor;
- abscisic acid (ABA);
- somatic embryogenesis;
- signal transduction;
- Daucus carota L.;
Seed dormancy is an important adaptive trait that enables seeds of many species to remain quiescent until conditions become favorable for germination. Abscisic acid (ABA) plays an important role in these developmental processes. Like dormancy and germination, the elongation of carrot somatic embryo radicles is retarded by sucrose concentrations at or above 6%, and normal growth resumes at sucrose concentrations below 3%. Using a yeast one-hybrid screening system, we isolated two bZIP-type transcription factors, CAREB1 and CAREB2, from a cDNA library prepared from carrot somatic embryos cultured in a high-sucrose medium. Both CAREB1 and CAREB2 were localized to the nucleus, and specifically bound to the ABA response element (ABRE) in the Dc3 promoter. Expression of CAREB2 was induced in seedlings by drought and exogenous ABA application; whereas expression of CAREB1 increased during late embryogenesis, and reduced dramatically when somatic embryos were treated with fluridone, an inhibitor of ABA synthesis. Overexpression of CAREB1 caused somatic embryos to develop slowly when cultured in low-sucrose medium, and retarded the elongation of the radicles. These results indicate that CAREB1 and CAREB2 have similar DNA-binding activities, but play different roles during carrot development. Our results indicate that CAREB1 functions as an important trans-acting factor in the ABA signal transduction pathway during carrot somatic embryogenesis.