β-1,3 Glucan Sulfate, but Not β-1,3 Glucan, Induces the Salicylic Acid Signaling Pathway in Tobacco and Arabidopsis
Abstract
Sulfate substituents naturally occurring in biomolecules, such as oligosaccharides and polysaccharides, can play a critical role in major physiological functions in plants and animals. We show that laminarin, a β-1,3 glucan with elicitor activity in tobacco (Nicotiana tabacum), becomes, after chemical sulfation, an inducer of the salicylic acid (SA) signaling pathway in tobacco and Arabidopsis thaliana. In tobacco cell suspensions, the oxidative burst induced by the laminarin sulfate PS3 was Ca dependent but partially kinase independent, whereas laminarin triggered a strickly kinase-dependent oxidative burst. Cells treated with PS3 or laminarin remained fully responsive to a second application of laminarin or PS3, respectively, suggesting two distinct perception systems. In tobacco leaves, PS3, but not laminarin, caused electrolyte leakage and triggered scopoletin and SA accumulation. Expression of different families of Pathogenesis-Related (PR) proteins was analyzed in wild-type and mutant tobacco as well as in Arabidopsis. Laminarin induced expression of ethylene-dependent PR proteins, whereas PS3 triggered expression of ethylene- and SA-dependent PR proteins. In Arabidopsis, PS3-induced PR1 expression was also NPR1 (for nonexpressor of PR genes1) dependent. Structure-activity analysis revealed that (1) a minimum chain length is essential for biological activity of unsulfated as well as sulfated laminarin, (2) the sulfate residues are essential and cannot be replaced by other anionic groups, and (3) moderately sulfated β-1,3 glucans are active. In tobacco, PS3 and curdlan sulfate induced immunity against Tobacco mosaic virus infection, whereas laminarin induced only a weak resistance. The results open new routes to work out new molecules suitable for crop protection.
PS3 and Lam5S were synthesized for this study. LamS(0.4), LamS(0.7), LamS(1.5), LamS(1.8), dLamS(2.4), CM-Lam, CurS, CurP, and fucan were obtained and described previously (Alban and Franz, 1994, 2000, 2001; Stibich, 2000; Alban et al., 2001; Klarzynski et al., 2003). DP, mean degree of polymerization; MM, molecular mass determined by gel permeation chromatography; DB, degree of C6 branching; n.d., no data.
Acknowledgments
We thank A.G. Darvill and S. Eberhard (Complex Carbohydrate Research Center, Athens, GA) for providing purified oligogalacturonate of DP 14, J. Mütterer (Institut de Biologie Moléculaire des Plantes, Centre National de la Recherche Scientifique, Strasbourg, France) for the microscopy analysis, R. Dietrich (Syngenta) for providing seeds of transgenic nahg Arabidopsis plants, and Altadis (Bergerac, France) for providing seeds of N. tabacum cv Samsun H. We thank also M. Seemanpillai and B. Dobay for English corrections. Most of the experiments with cultured tobacco cells were performed at Dijon (France) at the Unité Mixte de Recherche Plante-Microbe-Environnement headed by A. Pugin. We are particularly grateful to A. Pugin for his advice.
Notes
The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantcell.org) is: Serge Kauffmann (rf.gbsarts-u.plu-pmbi@nnamffuak.egres).
Article, publication date, and citation information can be found at www.plantcell.org/cgi/doi/10.1105/tpc.104.024968.