1983. Pathogen-induced vascular gels: Ethylene as a host intermediate. -Physiol. Plant. 59: 573-580. . ,, , . . . -, A cell-free culture filtrate from 6-day cultures of fttsaritttn oxysporum i. sp. cubense was processed to give: (1) a heterogeneous enzyme mixture, (2) purified polygalacturonase (PG), (3) partially-purified polygalacturonate lyase and (4) p-l,4-xylanase.When introduced into explanted castor bean leaves each of these preparations was able to promote the fonnation of vaseular system-obstructing gels. Exposure of castor bean leaves to ethylene (3 ppm) also triggered gel formation. Explanted leaves produced ethylene in response to the enzyme mixture and PG. Vascular gel formation did not occur when ethylene production in response to enzymes was prevented.Additional key word -Polygalacturonase. , .G. E. VartderMolen (reprint requests), J. E. DeVay, and L. L. Strand,

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Puified polygaacturonases from two fungi released proteins from wai fractions prepared from three plant species. Peroxidase activity was associated with the proteins released from the ceil wails, and several of the protein fractions released contained hydroxyproline. Ceilulase, purifled free of pectic enzyme activity, was ineffective in releasing ceil wail proteins. Specific inhibition of endopolygalacturonase activity prevented release of the proteins.Endopolygalacturonases and endopectate lyases, enzymes that degrade the galacturonate polymers of plant cell walls, cause cell death when applied to excised tissues (3,4,13,20), leaves and cuttings (5, 13), and intact plants (14). Peroxide appears to be involved in the endoPG2-induced damage to cotton leaf tissue (13). Peroxidases are associated with plant cell walls (2,16,17, 24), and are released from isolated cell walls by purified endopectate lyase (3) and purified endoPG (22). Release of peroxidases from cell walls may be important in the endoPG-induced damage of some plant tissues. In addition, the release of proteins by pectic enzymes is important to our understanding of the localization of proteins in plant cell walls and could be a means of obtaining cell wall proteins in a relatively native state. We have studied the release of wall proteins using cell walls from three plant species and purified pectic enzymes from two fungi. MATERIALS AND METHODSCell Wail Preparation. A modification of Barnett's technique (2) was used to prepare cell walls from potato tuber tissues, carrot xylem parenchyma, and etiolated cotton hypocotyls. Potato tubers and carrots were purchased locally. Cotton hypocotyls were grown in the dark for 8 days in Jiffy-Mix (Jiffy Products of America, West Chicago, Ill.) at 26 to 29 C. Excised tissues were homogenized in a chilled Sorvall Omni-Mixer for 2 min in 0.1 M sodium phosphate, pH 7.4, containing 1% (v/v) 1-octanol. Homogenized material was rinsed on Miracloth with several liters of ice-cold deionized H20, suspended in 100 ml of the phosphate buffer containing 2 M NaCl, and allowed to stand for at least 30 min at 4 C. The cold water rinse was repeated, and the osmotically shocked material was passed through a prechilled French pressure cell at 10,000 to 12,000 p.

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