Removal of the fibrillar network surrounding Cichorium somatic embryos using cytoskeleton inhibitors: analysis of proteic components

In Cichorium '474', the embryo globular stage was characterised by a fibril lar network linking peripheral neighbouring cells. To test a putative conne ction between this fibrillar network and the cytoskeleton (CTK), we have us ed CTK disrupting agents (cold; colchicine; cytochalasine B) on Cichorium s omatic embryos. Scanning electron microscopy observations showed that these three treatments induced the disappearance of the fibrillar network and su ggested that this network could take part of the CTK-plasma membrane (PM)-e xtracellular matrix (ECM) continuum. The treatment media containing the rem oval fibrillar network were used to analyse its proteic component by 2D-PAG E. Using a Sun SPARCstation computer, the comparison of the gels correspond ing to the different treatments allowed us to detect a group of 25 common p roteins recovered in the medium after each treatment and in somatic embryog enesis conditioned medium. During the short treatments applied on somatic e mbryos, a large amount of high molecular weight glycoproteins corresponding to arabinogalactan proteins (AGPs) have been quantified with beta-D-glucos yl Yariv reagent and identified with monoclonal antibodies raised against A GP epitopes (JIM13, JIM16, LM2). The implication of the fibrillar network a nd AGPs in the continuum CTK-PM-ECM are discussed in attempt to elucidate t heir possible function during Cichorium somatic embryogenesis. (C) 2000 Els evier Science Ireland Ltd. All rights reserved.