Comparison of the Ability of Partially N-Acetylated Chitosans and Chitooligosaccharides to Elicit Resistance Reactions in Wheat Leaves

• Published in: Plant physiology (Bethesda) Vol. 118; no. 4; pp. 1353 - 1359
• Main Authors: Peter Vander, Kjell M. Vårum, Alain Domard, El Gueddari, Nour Eddine, Moerschbacher, Bruno M.
• Format: Journal Article
• Language: English
• Published: Rockville, MD American Society of Plant Physiologists 01-12-1998; American Society of Plant Biologists
• Subjects: Biological and medical sciences; Cell walls; Chitin; Enzymes; Fundamental and applied biological sciences. Psychology; Fungal plant pathogens; Leaves; Lignification; Lignin; Oligomers; Pathology, epidemiology, host-fungus relationships. Damages, economic importance; Phytopathology. Animal pests. Plant and forest protection; Plant-Microbe and Plant-Insect Interactions; Plants; Polymers; Wheat; Lignin; Monocotyledones; Phenylalanine ammonia-lyase; Plant pathogen; Lyases; Biosynthesis; Cereal crop; Necrosis; Fungi; Disease resistance; Enzymatic activity; Gramineae; Angiospermae; Elicitation; Peroxidase; Acetylation; Thallophyta; Enzyme; Polymerization; Host agent relation; Chitin; Plant leaf; Carbon-nitrogen lyases; Ammonia-lyases; Sensitivity resistance; Peroxidases; Defense mechanism; Spermatophyta; Oxidoreductases; Chitosan; Comparative study; Triticum aestivum
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.118.4.1353

Chitin, a linear polysaccharide composed of (1→4)-linked 2-acetamido-2-deoxy-β-D-glucopyranose (GlcNAc) residues, and chitosan, the fully or partially N-acetylated, water-soluble derivative of chitin composed of (1→4)-linked GlcNAc and 2-amino-2-deoxy-β-D-glucopyranose (GlcN), have been proposed as elicitors of defense reactions in higher plants. We tested and compared the ability of purified (1→4)-linked oligomers of GlcNAc (tetramer to decamer) and of GlcN (pentamer and heptamer) and partially N-acetylated chitosans with degrees of acetylation (DA) of 1%, 15%, 35%, 49%, and 60% and average degrees of polymerization between 540 and 1100 to elicit phenylalanine ammonia-lyase (PAL) and peroxidase (POD) activities, lignin deposition, and microscopically and macroscopically visible necroses when injected into the intercellular spaces of healthy, nonwounded wheat (Triticum aestivum L.) leaves. Purified oligomers of (1→4)-linked GlcN were not active as elicitors, whereas purified oligomers of (1→4)-linked GlcNAc with a degree of polymerization ≥ 7 strongly elicited POD activities but not PAL activities. Partially N-acetylated, polymeric chitosans elicited both PAL and POD activities, and maximum elicitation was observed with chitosans of intermediate DAs. All chitosans but not the chitin oligomers induced the deposition of lignin, the appearance of necrotic cells exhibiting yellow autofluorescence under ultraviolet light, and macroscopically visible necroses; those with intermediate DAs were most active. These results suggest that different mechanisms are involved in the elicitation of POD activities by GlcNAc oligomers, and of PAL and POD activities by partially N-acetylated chitosan polymers and that both enzymes have to be activated for lignin biosynthesis and ensuing necrosis to occur.