The Enzymatic Activity of Fungal Xylanase Is Not Necessary for Its Elicitor Activity

AUTOR(ES)

Enkerli, Jürg

FONTE

American Society of Plant Physiologists

RESUMO

Fungal xylanases from Trichoderma spp. are potent elicitors of defense responses in various plants. To determine whether enzymatic activity is necessary for elicitor activity, we used site-directed mutagenesis to reduce the catalytic activity of xylanase II from Trichoderma reesei. For this, the glutamic acid residue at position 210, which is part of the active center in this family of enzymes, was changed to either aspartic acid (E210D) or serine (E210S). Wild-type and mutated forms of xylanase II were expressed in yeast cells and purified to homogeneity. Compared with the wild-type form of xylanase II, E210D had >100-fold and E210S 1,000-fold lower enzymatic activity. In contrast, these mutated forms showed no comparable drop in elicitor activity. They fully stimulated medium alkalinization and ethylene biosynthesis in suspension-cultured tomato (Lycopersicon esculentum) cells, as well as hypersensitive necrosis in leaves of tomato and tobacco (Nicotiana tabacum) plants. These results provide direct evidence that enzyme activity is not necessary for elicitor activity of fungal xylanase.

Documentos Relacionados

• The Receptor for the Fungal Elicitor Ethylene-Inducing Xylanase Is a Member of a Resistance-Like Gene Family in Tomato
• A Point Mutation in the Ethylene-Inducing Xylanase Elicitor Inhibits the β-1-4-Endoxylanase Activity But Not the Elicitation Activity1
• MEK kinase activity is not necessary for Raf-1 function
• Rotavirus RNA replication: VP2, but not VP6, is necessary for viral replicase activity.
• The Elicitation of Ethylene Biosynthesis by a Trichoderma Xylanase Is Not Related to the Cell Wall Degradation Activity of the Enzyme.