High-Affinity Binding Proteins for N-Acetylchitooligosaccharide Elicitor in the Plasma Membranes from Wheat, Barley and Carrot Cells: Conserved Presence and Correlation with the Responsiveness to the Elicitor

Abstract

Binding experiments as well as affinity labeling with an (125)I-labeled 2-(4-aminophenyl)ethylamino derivative of N-acetylchitooctaose revealed the presence of high-affinity binding sites/proteins for N-acetylchitooligosaccharide elicitor in the plasma membrane preparation from suspension-cultured carrot cells, barley cells and wheat leaves. Their binding specificity corresponded with the elicitor activity of N-acetylchitooligosaccharides and related sugars in these plant cells/tissues, and was similar to that reported for the binding site/protein previously reported for suspension-cultured rice cells. The molecular size of the binding proteins identified in carrot, barley and wheat was slightly smaller than that of rice. These plant cells were shown to respond to N-acetylchitooligosaccharides and generate reactive oxygen species, induced medium alkalinization, or previously shown to initiate lignification (wheat leaves, Barber et al. (1989) Physiol. Mol. Plant Pathol. 34: 3). No elicitor-binding protein nor the elicitor-induced cellular responses was detected for a cell line of tobacco BY-2 (BY-2T). On the other hand, another cell line of tobacco BY-2 (BY-2N) showed the presence of elicitor-binding protein and also elicitor-induced medium alkalinization. Thus, there was a good correlation between the existence of high-affinity binding proteins for the elicitor and elicitor-induced cellular responses among tested plant cells. These results indicated the wide distribution of N-acetylchitooligosaccharide elicitor-binding protein among various plants and added further support for the function of these plasma membrane proteins in the perception of the elicitor signal.

Plant cells recognize chitin fragments for defense signaling through a plasma membrane receptor

“…Similar binding proteins were also detected in various plant cells that could respond to the elicitor (8,9). Correlation between the presence of the binding proteins and the elicitor responsiveness of these cells, correlation between the binding specificity and the preference of the structure of chitin oligosaccharides in defense responses, strongly indicated that the binding proteins function as a receptor, or a part of receptor complex, for chitin oligosaccharide elicitor.…”

Size, acetylation and concentration of chitooligosaccharide elicitors determine the switch from defence involving PAL activation to cell death and water peroxide production in Arabidopsis cell suspensions

“…Whether chitosan oligomers killed cells by activating an H 2 O 2 -independent PCD or simply by necrosis is still unknown in our system. Unlike N-acetyl-chitooligosaccharides for which a receptor has been identified (Okada et al 2002), the way chitosan oligomers are perceived by plant cells is still unknown and often considered as a non-specific interaction of a polycation with negatively charged plasma membrane phospholipids that mimics and activates a common MAP kinase-dependent defence response (Shibuya and Minami 2001).…”

“…Similarly, the availability of chitinases and other chitin hydrolytic or binding activities in the plant cell wall could drastically reduce the elicitor concentration effectively perceived by the protoplast. The level of expression of oligochitin receptors (Bradley Day et al 2001, Okada et al 2002, or of other oligochitin-binding proteins Claeson 2003, Peumans et al 2003), could be developmentally regulated and also explain the discrepancies between different plant models (cell suspensions, seedlings and whole plants) and plant species. For example, Okada et al (2002) showed that carrot, wheat, barley, rice and tobacco BY-2N cells responded differently to N-acetyl-chitooligosaccharides, although their plasma membranes all contained a high-affinity binding site for N-acetyl-chitooligosaccharides.…”

“…N-acetylchitooligosaccharides bind to a specific receptor (Bradley Day et al 2001, Okada et al 2002 and induce membrane depolarization (Kuchitsu et al 1993, Kikuyama et al 1997, ion fluxes , the production of reactive oxygen species (ROS) (Kuchitsu et al 1995) and phytoalexin synthesis West 1992, Yamada et al 1993) in suspension-cultured rice cells. They also elicit lignification in wheat (Barber et al 1989), ion flux and protein phosphorylation in cultured tomato cells (Felix et al 1993), chitinase activity in melon (Roby et al 1987), phenylalanine ammonia-lyase (PAL) and tyrosine ammonia-lyase (TAL) activity in soybean leaves (Khan et al 2003) and glucanase gene transcription in cultured barley cells (Kaku et al 1997).…”

A Plasma Membrane Protein from Zea mays Binds with the Herbivore Elicitor Volicitin

“…Using radiolabeled b-1,3-glucan and hepta-b-glucoside elicitors characterized from fungal cell walls of Phytophthora megasperma f sp glycinea (Schmidt and Ebel, 1987), high affinity binding proteins have been identified in isolated legume plasma membrane fractions (Cheong and Hahn, 1991;Cote et al, 2000). Elicitor binding receptors for the N-acetylchitooligossaccharide elicitor have also been detected in plasma membrane fractions from several plant species including Oryza sativa (rice), Triticum aestivum (wheat), Hordeum vulgare (barley), and Daucus carota (carrot) (Okada et al, 2001(Okada et al, , 2002. Each of these pathogen elicitor-plant receptor interactions is characterized by nanomolar EC 50 concentrations as well as K d values in the low nanomolar range.…”