EXPRESSION OF THE JIM8 CELL-WALL EPITOPE IN CARROT SOMATIC EMBRYOGENESIS

Certain single cells in carrot (Daucus carota L.) suspension cultures react with the monoclonal antibody JIM8, and it has been proposed that these cells represent a transitional stage in somatic embryo formatio n. Shortly after isolation of the single cells by sieving, up to 80% o f the cells react with JIM8. Within 4 d, JIM8 labelling becomes restri cted to 1% of the single cells. To obtain evidence for the proposed co rrelation between expression of the JIM8 cell wall epitope and somatic embryo formation the developmental fate of carrot single cells labell ed with JIM8 was determined by cell tracking. The results, obtained by recording 43 000 cells, show that only few JIM8-labelled cells give r ise to embryos, and most somatic embryos develop from cells devoid of the JIM8 cell wall epitope. We therefore conclude that the presence of the JIM8 cell wall epitope does not coincide with the ability of sing le suspension cells to form embryos.