Hydrogen peroxide mediates defence responses induced by chitosans of different molecular weights in rice

• Published in: Journal of plant physiology 2005-08, Vol.162 (8), p.937-944
• Main Authors: Lin, Wuling, Hu, Xiangyang, Zhang, Wenqing, John Rogers, W., Cai, Weiming
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; beta-glucanase; Biological and medical sciences; cell suspension culture; Cells, Cultured; chitinase; chitosan; Chitosan - analogs & derivatives; Chitosan - pharmacology; CHN; Classical and quantitative genetics. Population genetics. Molecular genetics; cultured cells; Defence response; disease resistance; Fundamental and applied biological sciences. Psychology; fungal diseases of plants; gene expression regulation; Gene Expression Regulation, Plant - immunology; Generalities. Genetics. Plant material; Genetics and breeding of economic plants; grain crops; H 2O 2; hydrogen peroxide; Hydrogen Peroxide - metabolism; Magnaporthe - immunology; Magnaporthe grisea; Molecular genetics; Molecular Weight; Oryza - immunology; Oryza - physiology; Oryza sativa; pathogenesis-related proteins; phenylalanine ammonia-lyase; Phenylalanine Ammonia-Lyase - metabolism; plant biochemistry; Plant Diseases - microbiology; plant pathogenic fungi; plant physiology; plant proteins; Plant Proteins - biosynthesis; resistance mechanisms; Rice; seedlings; Seedlings - physiology; transcription (genetics)
• ISSN: 0176-1617; 1618-1328
• DOI: 10.1016/j.jplph.2004.10.003

To investigate the mechanisms whereby treatment with chitosan (CHN) is observed to increase the capacity of plants to resist pathogens, CHNs of different molecular weights (MWs) prepared by enzyme hydrolysis were used to treat rice cells in suspension culture and also rice seedlings. The results obtained with cultured cells showed that in this material CHN treatment could trigger a set of defence responses, including the production of hydrogen peroxide (H 2O 2), increases in the activities of phenylalanine ammonialyase (PAL; EC 4.3.1.5) and chitinase (CHI; EC 3.2.1.14), increases in transcription of defence-related genes β -1,3-glucanase ( glu) and chitinase ( chi) and accumulation of pathogen-related protein (PR1). Furthermore, CHNs of different MWs were observed to have different capacities to induce defence responses. CHNs of low MWs were more effective at inducing the described defence responses than those of higher MWs. Enhanced defence against rice blast pathogen Magnaporthe grisea 97-23-2D1 was observed in rice seedlings treated with low MW CHNs compared to seedlings treated with higher MW CHNs. In all cases, suppressing the production of H 2O 2 by adding scavengers dimethylthiourea (DMTU), 2,5-dihydroxycinnamic acid methyl ester (DHC), catalase (Cat) or ascorbate (As) blocked the defence responses. These results indicate that CHNs of low MWs have a greater capacity to induce the production of H 2O 2, thus resulting in stronger defence responses, than those with higher MWs.