ELICITOR-INDUCED SPRUCE STRESS LIGNIN - STRUCTURAL SIMILARITY TO EARLY DEVELOPMENTAL LIGNINS

Suspension cultures of Picea abies (L.) Karst released polymeric mater ial into the culture medium when treated with an elicitor preparation from the spruce needle pathogen Rhizosphaera kalkhoffii. The presence of lignin (about 35%, w/w) was demonstrated by phloroglucinol/HCl reac tivity and quantitation with thioglycolic acid. Carbohydrate (about 14 %, w/w) and protein (about 32%, w/w) were also detected. Amino acid an alysis revealed that hydroxyproline and proline predominated. Thioacid olysis and subsequent Raney nickel desulfurization allowed the analysi s of lignin-building units and interunit bonds. Compared with spruce w ood lignin, an approximately 20-fold higher relative amount of p-hydro xyphenyl units was determined. A high content of p-hydroxyphenyl units is typical for certain developmental lignins, such as conifer compres sion wood and middle lamella lignins, as well as all induced cell cult ure lignins so far analyzed. Cross-linkages of the pinoresinol type (b eta-beta) in the excreted cell culture lignin were markedly increased, whereas beta-1 interunit linkages were decreased relative to spruce w ood lignin. The amount and nature of cross-linkages were shown to be i ntermediate between those in wood lignin and in enzymatically prepared lignins. In summary, the elicitor-induced stress lignin was excreted as a lignin-extensin complex that closely resembled early developmenta l lignins.