Extracellular β-1,3-glucanases are induced during early somatic embryogenesis in Cichorium

Abstract

In leaf tissues of the Cichorium hybrid clone '474' (C. intybus L. var. sativum x C. endivia L. var. latifolia), the acquisition and expression of embryogenic competence was characterised by the appearance of 15 polypeptides (Boyer et al., 1993, Plant Sci 93: 41-53). The 38-kDa proteins were found to be abundantly present in conditioned embryogenic medium after the first division of the induced cells. These proteins seemed to be glycosylated as indicated by general carbohydrate detection methods. Internal amino-acid sequences obtained after microsequencing tryptic peptides appeared to be 36-57% homologous with plant beta-1,3-endoglucanases. In addition, these 38-kDa proteins were recognised by antibodies raised against the pathogenesis-related tobacco glucanase PR2a and their beta-1,3-glucanase activity was demonstrated by direct detection in polyacrylamide gels after electrophoresis. These results strongly suggested that the 38-kDa somatic-embryogenesis-related (SER) polypeptides are beta-1,3-glucanases. Moreover, the level of glucanase activity was nearly three times higher in the medium of the embryogenic '474' line than in the medium of a non-embryogenic line. The possible involvement of the extracellular 38-kDa proteins in callose degradation during somatic embryogenesis is discussed.

Arabinogalactan-proteins in Cichorium somatic embryogenesis: effect of β-glucosyl Yariv reagent and epitope localisation during embryo development

“…To study extracellular proteins, conditioned medium from embryo cultures was passed through a Falten®lter (MN 7131/4; Osi, Elancourt, France) and then through a Millipore 0.22-lm ®lter, dialysed for 72 h against distilled water, and lyophilised. Protein extraction was performed as described by Helleboid et al (1998) and samples were stored at )70°C until analysis. The presence of AGPs in Cichorium somatic embryogenesis conditioned culture medium was tested for by single radial diusion (Van Holst and Clarke 1985).…”

“…During Cichorium somatic embryogenesis, previous works have shown that extracellular protein patterns changed and were associated with the induction and initiation of somatic embryogenesis. Some of these proteins, named somatic embryogenesis related (SER) proteins (Hilbert et al 1992;Boyer et al 1993), have been identi®ed as extracellular b-1,3-glucanases (Helleboid et al 1998), chitinases and osmotin-like proteins (Helleboid et al 2000). As part of our programme to study protein markers of somatic embryogenesis, the biological activity of bGlcY was investigated by examining its eects on the induction of Cichorium somatic embryogenesis.…”

Recent progress in the understanding of tissue culture-induced genome level changes in plants and potential applications

“…Biochemical activity of cell wall enzymes such as b-1,3-glucanases in chicory (Helleboid et al 1998;2000), cell wall and membrane associated proteoglycan proteins such as glucosamine-and acetylated glucosamine-containing arabinogalactan proteins in carrot (van Hengel et al 2001), abscisic acid (ABA) inducible expression of embryo-specific globulin protein in maize (Duncan et al 2003), and germin-like proteins in conifer cultures (Mathieu et al 2006) are found to be associated with somatic embryo induction. Recently, a mutant Arabidopsis was identified with an inability to regenerate shoots in in vitro culture, attributed to a defect in fasciclin-like arabinogalactan protein expression (Johnson et al 2011).…”

Somatic embryogenesis in Araucaria angustifolia

“…specially of class IV) are able to cleave glycosidic bond of glucosamine and N-acetylglucosamine residues present in the sugar moiety of arabinogalactan proteins (Van Hengel et al 2001) generating oligossacharide signal molecules essential for early stages of plant embryogenesis (Malinowski and Filipecki 2002). In embryogenic cultures of Cichorium, the presence of a β-1,3 glucanase (37.7 kDa) positively correlated with the formation of SE (Helleboid et al 1998). The presence of extracellular chitinases and β-1,3-glucanases might be considered an indicator of a genotypic superiority of clone Ar5 for the development of SE.…”