Coordinate gene expression during somatic embryogenesis in carrots.

There are several biochemical differences between the callus and the embryos of carrot culture. Callus tissue produces callus-specific proteins and a conditioning factor that is necessary for the synthesis of callus-specific proteins. By contrast, embryos produce embryo-specific proteins [Sung, Z. R. & Okimoto, R. (1981) Proc. Natl. Acad. Sci. USA 78, 3683-3687] and develop the capability to inactivate cycloheximide [Sung, Z. R., Lazar, G. J. & Dudits, D. (1981) Plant Physiol. 68, 261-264]. A mutant, WCH105, that can inactivate cycloheximide in the callus as well as in the embryos produces the embryo-specific proteins instead of the callus-specific proteins and fails to produce the conditioning factor by the callus tissue. Callus tissues also produce a conditioning factor for callus growth. This factor is not the same as the conditioning factor for the synthesis of the callus-specific proteins, as WCH105 can grow as callus. The existence of WCH105 demonstrates that the callus-specific and embryo-specific traits are coordinately regulated, but in an opposite manner. A common mechanism apparently activates one set and inactivates the other set of functions. WCH105 seems to be impaired in this mechanism.