Polymethylgalacturonase Research Articles

Effect of coronatine on the induction of cell wall degrading enzymes in potato tuber discs.

Activities of cellulase, polygalacturonase (PG) and polymethylgalacturonase (PMG) in potato tuber discs treated with coronatine, an extracellular toxin produced by Pseudomonas syringae pv. atropurpurea (Reddy and Godkin) Young et al., were determined as an approach to the mechanism of hypertrophy induced by the toxin. The optimum pHs of cellulase, PG and PMG were around 5.0, 4.0 and 5.0, respectively. All these enzyme activities were considerably increased by coronatine treatment. Cellulase, PG or PMG was little altered, partially inhibited or slightly enhanced, respectively, by the addition of Ca++. The hypertrophy induced by coronatine can be partly explained in terms of the loosening of cell wall due to the increased activities of cellulase, PG and PMG.

Fusarium oxysporum f. sp. nicotianae Enzyme Production on Cell Walls Isolated from Meloidogyne incognita-Infected and Healthy Tobacco Roots

SUMMARYFusarium oxysporum f. sp. nicotianae was grown on cell walls from the roots of the flue-cured tobacco cultivars ‘Coker 298’ (resistant to Fusarium) and ‘Virginia Gold’ (susceptible to Fusarium). All plants were grown in a split-root system and Meloidogyne incognita eggs were applied to one-half of the root system of certain ‘Coker 298’ plants. The amounts of polygalacturonase, cellulase, polygalacturonate transeliminase, pectinmethyl transeliminase, polymethyl galacturonase and amylase enzyme activities and soluble protein concentrations produced by the fungus on cell wall preparations from these roots did not differ statistically. However, there was a strong tendency for greater enzyme activity production on cell walls from the nematode-infected roots than on walls from nematode-free roots.

Physiology of the tomato mutant alcobaca

Abstract Alcobaca is commonly regarded as an abnormally ripening mutant of the tomato (Lycopersicon esculentum Mill.). Alcobaca fruits were found to be similar to cv. Rutgers fruits in the following characteristics: time between full anthesis and the onset of ripening, response to ethephon, flavor, pH and concentrations of titratable acids, total soluble solids and reducing sugars. The pattern of CO2 and ethylene climacteric are similar in the two plant types, but the peak levels were lower and occurred later in alcobaca than in ‘Rutgers’. The mutant fruits differed from fruits of normal varieties in their greatly prolonged shelf life, their relatively low activity of polygalacturonase (PG) and polymethylgalacturonase (PMG), and their low level of endogenous ethylene. Fruits of the mutant harvested before the onset of ripening failed to reach normal pigmentation and remained yellow. Fruits harvested at the onset of ripening reached an orange color, while fruits ripened while attached to the plant reached almost normal pigmentation. These results suggest that alcobaca is a slow ripening mutant and does not belong to the category of non‐ripening mutants.

A comparison of the production of extracellular enzymes and rotting of apples by Pezicula alba and P. malicorticis

Pectolytic enzymes were found to be more readily produced in liquid culture by P. malicorticis (Jacks.) Nannf. than by P. alba Guthrie. Filtrates from cultures of the former gave greater polygalacturonase (PG), polymethylgalacturonase (PMG) and maceration activities than P. album, but slightly less pectinesterase (PE) activity. Both fungi responded in some degree to increased amounts of pectin in the medium. Enzymes were not produced if nitrogen was absent but activity did not increase greatly with increasing N concentration. Cellulase was produced by both fungi if grown in media with cellulose as the carbon source; no evidence was obtained of the production of this enzyme in vivo. Rotted apple tissue contained less total pectin and water-insoluble pectin than sound tissue, the percentage reduction in rots caused by P. malicorticis being greater than that in rots caused by P. alba. No relationship was found between the content of pectic substances of apple tissue and the susceptibility of this tissue to rotting. Alcoholic extracts of immature fruits of Cox's Orange Pippin and Bramley's Seedling and of ripe fruits of Stoke Red inhibited the PG and macerating activities if incubated overnight with partially purified mixtures of enzymes obtained from liquid cultures. No inhibition was obtained after incubation with similar extracts of ripe fruits of Cox or Bramley.