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

Abstract

Direct somatic embryogenesis was induced in root tissues of the Cichorium hybrid '474' (C. intybus L. var. sativum x C. endivia L. var. latifolia). Addition of beta-D-glucosyl Yariv reagent (betaGlcY), a synthetic phenylglycoside that specifically binds arabinogalactan-proteins (AGPs), to the culture medium blocked somatic embryogenesis in a concentration-dependent manner with complete inhibition of induction occurring at 250 microM betaGlcY. The AGP-unreactive alpha-D-galactosyl Yariv reagent had no biological activity in this system. Upon transfer of 250 microM betaGlcY-treated roots to control conditions, somatic embryogenesis was recovered with a time course similar to that of control roots. The betaGlcY penetrated roots and bound abundantly to developing somatic embryos, to the root epidermis and the stele. Immunofluorescence and immunogold labelling using monoclonal antibodies (JIM13, JIM16 and LM2) revealed that AGPs were localised in the outer cell walls peripheral cells of the globular embryo. A spatio-temporal expression of AGPs appeared to be associated with differentiation events in the somatic embryo during the transition from the globular stage to the torpedo stage. To verify betaGlcY specificity, molecules that bound betaGlcY were extracted from treated conditioned medium and identified as AGPs by using the same monoclonal antibodies. In addition, AGPs were found to be abundantly present in the medium during embryogenic culture. All of these results establish the implication of AGPs in embryo development, and their putative role in somatic embryogenesis is discussed.

Characterization of Sugar Moieties of a Cell Division Factor from Tobacco 2B-13 Cells

“…If this sequence of events would be proven, an interesting signaling pathway downstream from the auxin application that results in the induction of cell division in plant cells would be demonstrated. This situation seems to have some similarity to what has been observed upon the somatic embryogenesis of carrot (Kreuger and van Holst 1995) and Chicorium (Chapman et al 2000), in which the addition of b-glucosyl Yariv reagent to the culture medium blocked somatic embryogenesis in a concentration-dependent manner, while the addition of agalactosyl Yariv reagent to the medium did not. Another example has been reported by Motose et al (2004), in which functions of xylogen having a role in tracheary element differentiation have been inhibited by b-glucosyl Yariv reagent.…”

Identification and Analysis of Differentially Expressed Genes During Seed Development Using Suppression Subtractive Hybridization (SSH) in Phaseolus vulgaris

“…PRP is considered to be a structural component of the cell wall, has been shown to be involved in many signaling pathways (Showalter 2001;Williamson 1994), and is reported to be essential for the formation of somatic embryos in Cichorium intybus (Chapman et al 2000). A particular PRP from maize (zmHyPRP) is specifically expressed in embryos (José-Estanyol et al 1992).…”

Protein expression during seed development in Araucaria angustifolia: transient accumulation of class IV chitinases and arabinogalactan proteins

“…Two particular modes of signaling systems, via auxin and cell wall components, are essential for the expression of genetic programs responsible for establishment of the apical-basal polarity (Souter and Lindsey 2000). A spatio-temporal expression of AGPs seems to be directly related to the determination of cell position and cell fate during embryo development (Chapman et al 2000).…”