Abstract
Phytosulfokine-α (PSK), a peptidyl plant growth factor, has been recognized as a promising intercellular signaling molecule involved in cellular proliferation and dedifferentiation. It was shown that PSK stimulated and enhanced cell divisions in protoplast cultures of several species leading to callus and proembryogenic mass formation. Since PSK had been shown to cause an increase in efficiency of somatic embryogenesis, it was reasonable to check the distribution of selected chemical components of the cell walls during the protoplast regeneration process. So far, especially for the carrot, a model species for in vitro cultures, it has not been specified what pectic, arabinogalactan protein (AGP) and extensin epitopes are involved in the reconstruction of the wall in protoplast-derived cells. Even less is known about the correlation between wall regeneration and the presence of PSK during the protoplast culture. Three Daucus taxa, including the cultivated carrot, were analyzed during protoplast regeneration. Several antibodies directed against wall components (anti-pectin: LM19, LM20, anti-AGP: JIM4, JIM8, JIM13 and anti-extensin: JIM12) were used. The obtained results indicate a diverse response of the used Daucus taxa to PSK in terms of protoplast-derived cell development, and diversity in the chemical composition of the cell walls in the control and the PSK-treated cultures.
Highlights
The genus Daucus belongs to the Apiaceae family recognized as one of the largest families of seed plants [1,2] and includes, following the newest taxonomical revision [2,3], about 40 species
Among arabinogalactan protein (AGP) epitopes the one recognized by the JIM4 antibody was not identified in the PSK-treated cultures but in the control cultures it was detected in very low amount in the form of single dots in the walls inside the cluster (Figure 8C,I) while the AGPs recognized by the JIM8 and JIM13 antibodies were abundantly present (Figure 8D,E,J,K)
Two species, i.e., D. montevidensis and D. pusillus, expressed strong recalcitrance to culture conditions by the arrest of cell divisions after only a few rounds of mitosis, while the remaining four wild forms were successfully regenerated with efficiencies not lower than those observed for the cultivated carrot
Summary
The genus Daucus belongs to the Apiaceae family recognized as one of the largest families of seed plants [1,2] and includes, following the newest taxonomical revision [2,3], about 40 species. These species may become a valuable source of genetic variability for the cultivated carrot Since the discovery of somatic embryogenesis in root-derived callus cultures in vitro [5,6], the carrot has become a model species for plant tissue culture systems. Despite the availability of many Daucus genetic resources mentioned above, so far only protoplasts isolated from one close relative, i.e., D. carota subsp. capillifolius (Gilli) Arbizu [11], have been fused in a symmetric/
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