Phytosulfokine- (PSK), a peptidyl plant growth factor, has been recognized as a promising intercellular signaling molecule involved in cellular proliferation and dedifferentiation. the correlation between wall regeneration and the presence of PSK during the protoplast culture. Three 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 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. 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. Theoretically, these species may become a valuable source of genetic variability for the cultivated carrot (L. subsp. Hoffm)the only cultivated species of the genus and the most important member of Apiaceae in terms of economic value and nutrition, second to the potato in worldwide vegetable production [2,4]. 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. Among various plant in vitro techniques, protoplast cultures offer a unique approach useful in crop improvement i.e., protoplast fusion-based somatic hybridization/cybridization (reviewed in Eeckhaut et al.  and Wang et al. ). Research on protoplast cultures began when parallel successful protoplast isolation from carrot roots  and from cell suspensions  were reported. Despite the availability of many genetic resources mentioned above, so far only protoplasts isolated from one close relative, i.e., subsp. (Gilli) Arbizu , have been fused in a symmetric/asymmetric way with protoplasts of the cultivated carrot [12,13]. In general, the ability to regenerate plants from fused protoplasts is a fundamental reason for the limited use of somatic hybridization/cybridization. Therefore, before applying this procedure to plant breeding programs, an efficient protoplast-to-plant-system for both fusion partners should be accessible. There are several reports on successful plant regeneration from carrot protoplasts with respect to different types of source tissue [10,14,15] and to the best of our knowledge, only one with regard to wild species, showing extremely different reactions of the examined accessions Hyodeoxycholic acid to the culture, ranging from highly responsive to recalcitrant . Several parameters influence the ability of protoplasts and protoplast-derived cells to express their totipotency and to develop into fertile plants . Re-synthesis of the cell wall is one of the most important key steps in the protoplast development preceding mitotic divisions and initiating the establishment of a protoplast-to-plant system. Protoplast-based approaches are not only a convenient tool for plant improvement but they also provide a good model for studies in plant physiology, pathology, molecular biology, cytogenetic  as well as for studying the correlation between cell-wall composition and cell differentiation . It is postulated that the cell-wall composition and the changes to which it is subjected during differentiation, redifferentiation and dedifferentiation reflect morphogenetic events during plant development [19,20,21]. Application of protoplast cultures to plant improvement requires knowledge from different disciplines and familiarity with factors involved in developmental processes. It is known, that among the factors involved in these processes, the cell wall chemical components and their molecular organization are of special interest [19,22]. Different methods have been used to determine the chemical composition during cell wall regeneration [23,24,25]. However, to answer the question of Hyodeoxycholic acid the spatial location of individual chemical components in the wall during the regeneration process, it is necessary to BPTP3 use immunohistochemical methods. Thus, application of monoclonal antibodies (mAbs) against pectic, arabinogalactan proteins (AGPs) and extensins epitopes allows us to indicate the precise distribution of these components in muro [19,21,26,27]. So far our knowledge concerning spatio-temporal distribution Hyodeoxycholic acid of wall components during the wall regeneration is scarce. Among the few existing reports referring to this issue, the presence of pectic, xyloglucan and carbohydrate AGP epitopes in leaf-derived protoplasts of the sugar beet (L.) was described [19,28]. In later studies, Wi?niewska and Majewska-Sawka  confirmed the presence of some AGPs and pectins in the reconstituted cell wall.