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Tham khảo tài liệu 'cell metabolism cell homeostasis and stress response part 2', khoa học tự nhiên, công nghệ sinh học phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 6 Cell Metabolism - Cell Homeostasis and Stress Response fungi or plant cell wall fragments and then a biological response could be the main factor determining the survival or decline of plants. Many fungal pathogens have P-glucans as major components of their cell walls which are recognized by different plant species Yoshikawa et al. 1993 . The Albersheim working group at the middle of 70 s was the first to extract glucans elicitors of phytoalexins a natural antimicrobial compound in soybean from the mycelial walls of Phytophthora megasperma by heat treatment. These fungal wall structures were analyzed by Sharp et al. 1984 detailing the primary structure of an active glucan from Phytophthora megasperma f. sp. glycinea Pmg obtained by partial acid hydrolysis finding that the hepta-P-glucoside elicitor was the active subunit. Partial characterization of the fraction with elicitor activity from Pmg walls showed P-glucans with terminal residues 1-3 42 1-6 2 and 1-3 1-6 27 glycosidic bonds Sharp et al. 1984 Waldmuller et al. 1992 . They observed that the obtention method of the cell wall fragments influenced the type of links present in the fungal elicitor. If the elicitor is released naturally or by heat treatment then elicitors differ greatly from those glucans obtained by partial acid hydrolysis. While naturally released glucans have P- 1-3 1-6 ramifications P- 1-6 links are in greater proportion when glucans are released from acid hydrolysis Waldmuller et al. 1992 . 5.3 Oligoglucan receptors in plants The recognition of elicitors by plants could be possible if the oligoglucan-receptor interaction occurs Yoshikawa et al. 1993 . In plants receptors of fungal elicitors are found on the cell surface while bacterial receptors are found within the cell Ebel Scheel 1997 . Other binding sites for oligosaccharides glycopeptides peptides and proteins are located on the cell surface and in the membranes Cosio et al. 1990 . Hence many defense responses could be activated .
