Ethylene Biosynthesis-Inducing Xylanase

Abstract

The ethylene biosynthesis-inducing endoxylanase (EIX) from xylan-induced cultures of the fungus, Trichoderma viride, was purified to near homogeneity and compared with the EIX isolated from Cellulysin. Both enzymes migrate as 9.2 kilodalton proteins during gel filtration chromatography under nondenaturing conditions, but the mature polypeptide migrates as a 22 kilodalton band in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The amino acid composition of the 22 kilodalton polypeptide is enriched by Gly, Ser, Thr, Trp, and Tyr, but depleted in Ala, Glx, Leu, and Lys. Both proteins lack sulfur-containing amino acids. The protein is glycosylated, and inhibition of EIX synthesis by tunicamycin suggests that at least some of the sugar moieties are linked to asparagine residues. EIX appears to be synthesized initially as a 25 kilodalton precursor protein that is processed to 22 kilodalton during secretion.A factor limiting our understanding of plant defense responses in plant-pathogen interactions has been the paucity of elicitors which have been purified and structurally characterized. Ethylene biosynthesis, one common response of plant tissues to pathogen attack (21), is stimulated by a variety of plant-and pathogen-derived polysaccharides and proteins (4,26,28). Ethylene has been suggested to play a role in activating certain defense responses in some plant tissues (9). This laboratory has previously demonstrated that an endo-B-1,4-xylanase (1,4-f3-D-xylan xylanohydrolase; EC 3.2.1.8) purified from a commercial mixture of fungal enzymes, Cellulysin3, is a potent elicitor ofethylene biosynthesis in tobacco (Nicotiana tabacum L. cv Xanthi) ( 1,12).

The Receptor for the Fungal Elicitor Ethylene-Inducing Xylanase Is a Member of a Resistance-Like Gene Family in Tomato

“…Xylanase (Fluka, Milwaukee, WI) was purified as previously described (Dean and Anderson, 1991). In the plants, EIX (1 to 4 mg/mL) was injected into leaves using needleless syringes as previously described .…”

A Novel Plant Cysteine Protease Has a Dual Function as a Regulator of 1-Aminocyclopropane-1-Carboxylic Acid Synthase Gene Expression

“…Xylanase (Fluka, Milwaukee, WI) was purified as described previously (Dean and Anderson, 1991). EIX (2 to 5 mg/mL) was injected into leaves using needleless syringes as described previously .…”

“…Ethylene-Inducing Xylanase (EIX), a 22-kD protein elicitor (Dean and Anderson, 1991), elicits ethylene biosynthesis, hypersensitive response, and other defense responses in such plants as tomato (Lycopersicon esculentum) and tobacco (Nicotiana tabacum) (Bailey et al, 1992;Felix et al, 1993;Avni et al, 1994;Yano et al, 1998;Elbaz et al, 2002;Ron and Avni, 2004). The increase in ethylene biosynthesis is accompanied by the accumulation of 1-aminocyclopropane-1-carboxylic acid (ACC), an increase in extractable ACC synthase activity, and increases in Acs and ACC oxidase transcripts (Avni et al, 1994).…”

Nucleotide Sequence of the Nicotiana tabacum cv Xanthi Gene Encoding 1-Aminocyclopropane-1-Carboxylate Synthase

“…It has been known for some time that ACC synthase activity is enhanced in tobacco leaves undergoing a hypersensitive response to pathogen attack (3). An EIX produced by the fungus Trichoderma viride elicits ethylene biosynthesis in N. tabacum cv Xanthi leaf tissue (2). When EIX is applied to the petiole of a detached tobacco leaf, it moves throughout the leaf and, consequently, induces ethylene production and tissue necrosis (1).…”