Are extracellular matrix surface network components involved in signalling and protective function?

Abstract

Endosperm is an interesting model for in vitro experiments, because of its unique origin, development and ploidy level. Here we used Actinidia deliciosa endosperm-derived callus to investigate morphology, histology and chemistry of extracellular matrix (ECM) structures in morphogenically stable tissue from long-term culture. SEM and TEM analysis showed that ECM is a heterogenous layer which consists of amorphous, dark-staining material, osmiophilic granules and reticulated fibres outside the outer callus cell wall. This structure may serve as a structural marker of morphogenic competence in endosperm-derived callus, because of its presence on the surface of callus forming morphogenic domains and its disappearance during organ growth. Based on immunolabelling, histochemistry, solvent and enzyme treatments, we suggest that pectins and lipids are components of the ECM layer. These results might indicate protective, water retention and/or cell communication functions for this ECM layer.In several plants cultured in vitro, SEM analysis revealed that induction of morphogenesis is linked to the appearance of a fibrillar network referred to as the extracellular matrix surface network (ECMSN). 1 Šamaj et al., 2,3 reported, that the ECMSN plays an important morphoregulatory role during somatic embryogenesis and organogenesis, implying an active role in plant morphogenesis. According to Bobák et al., 4 the chemical composition and structural arrangement of the ECMSN on the cell surface indicate that it may play a fundamental role in cell-to-cell recognition and interaction, cell division and differentiation, and also in generation and maintenance of some traits in plant cell populations. There is not a large body of data confirming the occurrence of ECM during in vitro organogenesis. 5,6 Most data concern the formation, structure and chemical composition and function of ECM in somatic and androgenic embryogenesis (reviewed in refs. 6-10). In previous histological and SEM analysis of morphogenic endosperm-derived callus of A. deliciosa, we described the presence of a membranous layer covering the callus surface, which we termed extracellular matrix (ECM). 11 The present experiments employed SEM, TEM and histochemical analysis to study the structure and composition of material coating the callus surface.SEM revealed the presence of heterogeneous material covering the callus surface. A smooth membranous layer coated some parts of the callus surface (Fig. 1A), while other regions were covered by fibrillar structures and granules of mucilage-like secretion forming a network at site of cell-cell adhesion. Similar structures were observed during in vitro induction of somatic embryogenesis, androgenesis and organogenesis in different species (reviewed in refs. 7-13).TEM showed a layer composed of amorphous material with fibrillar and spherical components covering morphogenic cell clusters. The cell wall of non-embryogenic and senescent cells was also covered with ECM, but it differed in appearance: the layer was granular, with amo...

Histology, histochemistry and ultrastructure of pre‐embryogenic cells determined for direct somatic embryogenesis in the palm tree Syagrus oleracea

“…This event common to other embryogenic systems (Verdeil et al , Popielarska‐Konieczna et al ), according to Williams and Maheswaran (), prevents the interference of adjacent cells that are in the process of degeneration or determined to follow other pathways. Callose is naturally a physiological response common to different stressors (Zavaliev et al ), which supports the hypothesis that somatic embryogenesis is an adaptation response of the plant genome to the stress typical of culture in vitro (Karami and Said , Nowak and Gaj ).…”

Spatial Distribution of Selected Chemical Cell Wall Components in the Embryogenic Callus of Brachypodium distachyon

“…In addition, these two categories of cell wall compounds are detectable in the fibrillar network outside the outer periclinal walls, which is known as the extracellular matrix surface network (ECMSN) that is characteristic for SE [19, 26]. The detailed significance of this network is still under study, but it has been suggested that it participates in cell adhesion, cell signalling and in the regulation and coordination of somatic embryo development [27]. Hemicelluloses are polysaccharides that are composed of various monosaccharides such as glucose, mannose galactose, arabinose and xylose, which along with cellulose comprise the main component of plant cell wall.…”

Arabinogalactan proteins and the extracellular matrix surface network during peach palm somatic embryogenesis

“…Based on its composition and localization, different roles of the ECMSN have been proposed. One is related to cell adhesion and control of morphogenesis of a specific group of cells (Šamaj et al 2006, Popielarska‐Konieczna et al 2008a, 2008b). This proposal is supported by the multicellular origin of the somatic embryos in our regenerative system (Steinmacher et al 2007a, 2007c, 2011).…”

“…The mechanisms controlling the formation of the ECMSN remain largely unknown. However, it is believed that ECMSN is involved in the integration and recognition of morphogenic cells within multicellular callus domains, as well as having a protective function (Popielarska‐Konieczna et al 2008b). The composition of ECMSN includes proteins, pectidic polysaccharides, lipophilic substances and AGPs (Chapman et al 2000a, 2000d, Konieczny et al 2005, Namasivayam et al 2006, Popielarska‐Konieczna et al 2008a, Pan et al 2011).…”