Total protein pattern expression during induction and development of carrot somatic embryos

Differential gene expression revealed by the analysis of total protein patterns was investigated in somatic embryogenesis of Daucus carota L. The aim of this work was to identify markers, and to assess the relationships between induction and different developmental stages of somatic embryogenesis. Proteins extracted from an embryogenic cell suspension and five developmental stages of somatic embryos were separated by two-dimensional gel electrophoresis. Both quantitative and qualitative changes were detected, and the relationships between the protein patterns were visualized using an unrooted tree. The different organs of somatic plantlets, namely root, hypocotyl and cotyledon, were analyzed separately for spatial differences in protein distribution. A comparison of six protein patterns revealed that the variable proteins were modulated according to five profiles, three of which are most relevant. Among the variable proteins, ten were specific to the cell suspension stage and might be assigned either to callogenesis or to embryogenesis induction. Six proteins found only in somatic embryos were shown to fluctuate at different developmental stages and represent morphogenesis markers. Proteins absent during the early stages of embryo development but expressed in the cell suspension stage as well as in the later stages, might be correlated with the presence of 2,4-D. In fact, the unrooted tree revealed that the cell suspension protein pattern was closer to that of somatic plantlets than to earlier stages of embryogenesis. Furthermore, the CS pattern was closer to that of roots, which are auxin inducible, than to the other organ of the plantlet. Therefore, possible effects of exogenous and endogenous auxins on protein synthesis are discussed.