Biological Activity of Reducing-End-Derivatized Oligogalacturonides in Tobacco Tissue Cultures1

Abstract

The biological activity of reducing-end-modified oligogalacturonides was quantified in four tobacco (Nicotiana tabacum) tissue culture bioassays. The derivatives used were oligogalacturonides with the C-1 of their reducing end (a) covalently linked to a biotin hydrazide, (b) covalently linked to tyramine, (c) chemically reduced to a primary alcohol, or (d) enzymatically oxidized to a carboxylic acid. These derivatives were tested for their ability to (a) alter morphogenesis of N. tabacum cv Samsun thin cell-layer explants, (b) elicit extracellular alkalinization by suspension-cultured cv Samsun cells, (c) elicit extracellular alkalinization by suspensioncultured N. tabacum cv Xanthi cells, and (d) elicit H 2 O 2 accumulation in the cv Xanthi cells. In all four bioassays, each of the derivatives had reduced biological activity compared with the corresponding underivatized oligogalacturonides, demonstrating that the reducing end is a key element for the recognition of oligogalacturonides in these systems. However, the degree of reduction in biological activity depends on the tissue culture system used and on the nature of the specific reducing-end modification. These results suggest that oligogalacturonides are perceived differently in each tissue culture system.Carbohydrates that act as signal molecules in plants (oligosaccharins) have been isolated from plant and fungal cell wall polysaccharides, from the cell walls of bacterial symbionts of plants, and from fungal glycopeptides (for review, see Ryan and Farmer, 1991;Darvill et al., 1992;Cô té and Hahn, 1994). We are interested in determining the mechanism by which one type of the plant cell wallderived oligosaccharins, the oligogalacturonides, elicit biological responses in plants.The biological effects elicited in plants by oligosaccharins are diverse (for review, see Ryan and Farmer, 1991;Darvill et al., 1992;Cô té and Hahn, 1994) but can generally be placed in two groups: delayed responses and rapid responses. Delayed responses are usually observed hours or days after oligosaccharin treatment and are often directly involved in adaptation to environmental conditions, whereas rapid responses generally occur at the plant cell surface and are observed within minutes after addition of oligosaccharins. The delayed responses elicited by oligogalacturonides can be broadly divided into those in which defense responses are induced and those in which growth and development are modified. The defense-related responses, depending on the plant species, include phytoalexin accumulation (Hahn et al., 1981), lignification of cell walls (Robertsen, 1986), and proteinase inhibitor accumulation (Bishop et al., 1984). The responses involving growth and development include induction of ethylene in tomato fruit (Brecht and Huber, 1988), inhibition of auxin-induced pea stem elongation (Branca et al., 1988), and regulation of tobacco (Nicotiana tabacum) TCL explant morphogenesis (Eberhard et al., 1989). The rapid responses induced by oligogalacturonides include enhanced protein phosp...

Extracellular H2O2 Induced by Oligogalacturonides Is Not Involved in the Inhibition of the Auxin-Regulated rolB Gene Expression in Tobacco Leaf Explants

“…Because OGs have been shown to induce H 2 O 2 in several plant tissues and cells (Legendre et al, 1993;Svalheim and Robertsen, 1993;Levine et al, 1994;Mathieu et al, 1998;Spiro et al, 1998;Stennis et al, 1998;Orozco-Cardenas and Ryan, 1999), we determined whether this response also occurred in rolB-GUS explants. RolB-GUS explants were cultured in the presence of IAA (0.6 m), OGs (DP of 9-18; 10 g/mL), or water (controls) added at time 0 or 8 h later.…”

“…The earliest detectable responses induced by OGs are the activation of specific ion channels leading to influx of H ϩ and Ca 2ϩ and efflux of K ϩ (Messiaen and Van Cutsem, 1994;Mathieu et al, 1998;Spiro et al, 1998), and the transient formation of reactive oxygen species (ROS) such as O 2 Ϫ , H 2 O 2 , and ⅐OH (Svalheim and Robertsen, 1993;Levine et al, 1994). How OGs cause the generation of ROS is not known.…”

Pathogen-Induced Defense and Innate Immunity in Macroalgae

“…In addition to MAMPs, vascular plants also perceive breakdown products of their own cell wall that are released by glucohydrolytic activities from attacking phytopathogenic microbes; these breakdown products are called pathogen-induced molecular patterns (PIMPs; Mackey and McFall, 2006), or endogenous elicitors. For example, pectin oligosaccharides are established as elicitors of defense responses in vascular plants (Mathieu et al, 1991;Spiro et al, 1998;Nürnberger et al, 2004).…”

Criblage d\'inducteurs de réactions de défense chez le blé (<i>Triticum aestivum</i>) contre l\'oïdium (<i>Blumeria graminis f.sp. tritici</i>)

“…La protection obtenue avec le broyat foliaire serait due à la libération d'une multitude de composés inducteurs correspondant à des glucides associés à la paroi cellulaire comme les oligogalacturonides. En effet, ces composés ont été décrits comme inducteurs de réactions de défense chez les plantes (Albersheim et al, 1992 ;Creelman et Mullet, 1997 ;Spiro et al, 1998 …”