Healthy Plant Extracts Research Articles

Properties of the ribonucleotide kinases after infection of cucumber with tobacco ringspot virus

A rapid, convenient and reliable assay procedure has been developed for the investigation of the levels of activity and the properties of the ribonucleotide kinases (ATP: ribonucleoside monophosphate and diphosphate phosphotransferases, EC 2.7.4.4. and EC 2.7.4.6) in extracts of cucumber cotyledons infected with tobacco ringspot virus. The level of activity of UMP kinase increased 2–4 days after infection and rose to a level about twice that found in extracts of healthy plants. On the other hand, the level of activity of the other three mononucleotide kinases remained unchanged after infection. However, there were significant differences between the apparent K m values for each of the kinases in extracts of healthy and infected plants, but it has not yet been shown whether these differences are a consequence of some virus-induced alteration of the properties of the normal host enzymes or the virus-induced synthesis of virus-specific kinases. The constancy of the ratios of the nucleoside diphosphate to the nucleoside triphosphate (range 0.17–0.36) produced in assays of each of the mononucleotide kinases under a variety of conditions indicated that the conversion of the mono- to the diphosphate, and not the di- to the triphosphate was the rate-limiting reaction in extracts of both healthy and infected plants.

Separation of a highly active antiviral factor from virus-infected plants

An antiviral factor (AVF), which occurs in plants infected with tobacco mosaic virus, was separated by means of column chromatography. This inhibitor was eluted from diethylaminoethylcellulose by 0.56–0.58 M NaCl. At this concentration antiviral material was not eluted when extracts of healthy plants were used. This AVF is very active in reducing virus infectivity even at extremely low concentrations. Rough calculations indicated that the procedure of fractionation followed in this work, resulted in an increase of about 5000 times in AVF activity per unit protein, as compared to the starting material.

Chromatographic studies on plant viruses: I. The isolation of potato virus X by means of various systems of adsorption chromatography

This work was an attempt to find a successful method for isolating potato virus X which would distinguish clearly between diseased plants and healthy plants. Two methods were tried, but without success. The first was chromatography on calcium phosphate and the second was chromatography on DEAE-cellulose. A third method was then developed which gave distinct results. It involved chromatography on cellulose using polyethylene glycol and NaCl as solvent. Extracts of healthy tomato plants and those infected with potato virus X were clarified by low speed centrifugation. Potato virus X was separated from host components of these extracts by treatment with chloroform, precipitation at pH 4.5, dissolution at pH 7.0, adsorption on cellulose in a column from a solution containing 6% polyethylene glycol and 4.5% NaCl, and elution of the cellulose column with solutions containing stepwise decreasing concentrations of polyethylene glycol and NaCl. Most of the healthy plant components remaining after precipitation at pH 4.5 were eluted by solutions containing polyethylene glycol and NaCl at concentrations of 4.0 and 3.0%, or 3.5 and 2.6%, respectively. But the virus was eluted by solutions containing polyethylene glycol and NaCl at concentrations of 1 and 0.75%, or 0.5 and 0.37%, respectively.

THE OCCURRENCE IN THE HOST PLANT OF PHYSIOLOGICALLY ACTIVE GUMS PRODUCED BY CORYNEBACTERIUM INSIDIOSUM AND CORYNEBACTERIUM SEPEDONICUM

Corynebacterium insidiosum and Corynebacterium sepedonicum, the causative agents of bacterial wilt of alfalfa and of potato ring rot, produce viscous polysaccharide solutions when grown in shaken culture. These substances contain fucose, a sugar rarely found in polysaccharides of land plants. Hydrolyzates of polysaccharides extracted from alfalfa and potato plants infected with these organisms also contained fucose, while extracts of healthy plants did not. Alfalfa cuttings placed in dilute polysaccharide solutions wilted rapidly. These findings suggest that these polysaccharides are probably formed in the vascular systems of infected plants and that if such is the case they contribute to the development of the disease in these plants.