EFFECT OF AUXIN ON β-1, 3-GLUCANASE ACTIVITY IN AVENA COLEOPTILE

When the homogenate of Avena coleoptile segments was fractionated, the specific activity of β-1, 3-glucanase was remarkably associated with the cell wall, partly to be released from it by a detergent. The cell wall-bound glucanase activity was increased by the treatment of coleoptile segments with auxin. Only in 10 min of the treatment the glucanase activity and the incorporation of labeled leucine into the proteins were found to be increased in the fraction to be liberated by detergent from the cell wall fraction. These effects of auxin were inhibited by 10 μg/ml cycloheximide.     

EFFECT OF AUXIN AND OXALIC ACID ON THE CELL WALL PROPERTY OF AVENA COLEOPTILE

In accelerating the elongation of excised Avena coleoptile cylinders,the effect of oxalic acid was found to be additive to that ofindole-3-acetic acid. Elastic and plastic extensions of the coleoptile cylinder weremeasured by using the plasmolytic method. Both indole-3-aceticacid and oxalic acid increased the elastic extension quickly,while their effect in increasing the plastic extension appeared2 hours after their application. The mechanism of auxin action is discussed in connection withthe effect of removal of calcium from the pectic substance ofthe primary cell wall. (Received November 15, 1960; )     

THE GROWTH AND RESPIRATION OF THE AVENA COLEOPTILE

1. Transport of the plant growth hormone into the Avena coleoptile as well as the action of the hormone on cell elongation in the coleoptile are shown to depend upon aerobic metabolism. 2. Crystalline auxine, in contrast with impure preparations, affects neither the magnitude nor the respiratory quotient of coleoptile respiration. 3. Increasing age of the coleoptile cell decreases its rate of elongation much more than its rate of respiration. HCN or phenylurethane on the other hand decrease the two processes to the same extent, in spite of the fact that only a small portion of the energy liberated by respiration can be used in the mechanical process of growth. 4. From 2 and 3 it is concluded that processes of a respiratory nature but of relatively small magnitude form one or more integral steps in the chain of reactions by which the plant growth hormone brings about cell elongation.     

INTRACELLULAR LOCALIZATION OF PHENOL SULPHOTRANSFERASE IN RAT BRAIN

—The intracellular localization of phenol sulphotransferase in rat brain was studied The distribution pattern found after differential centrifugation closely resembles that of lactate dehydrogenase and does not change during postnatal development. The distribution of the enzyme in discontinuous and continuous sucrose gradients, however, shows a deviation from the lactate dehydrogenase pattern and a shift towards a higher sucrose concentration during development. In the adult the phenol sulphotransferase coincides with monoamine oxidase, succinate dehydrogenase and β-glucuronidase. Disruption experiments, purification of mitochondria and electron microscopy exclude localization of phenol sulphotransferase in mitochondria. These studies support the idea of phenol sulphotransferase as a cytoplasmic enzyme with a preferential binding to or localization in oligodendroglial cells or, more probably, a specific type of synaptosomes.     

INTRACELLULAR LOCALIZATION OF KYNURENINE IN THE FATBODY OF DROSOPHILA

Light blue fluorescent globules accumulate in the cells of the anterior region of the fatbody of Drosophila larvae near the time of pupation. This fluorescent material appears in the Ore-R wild type strain as well as mutant strains in which the synthesis of both the red and brown eye pigments is affected. The vermilion mutant, which is characterized by the absence of the brown pigment component in the eye, was the only strain among those examined which did not develop the light blue fluorescent globules. Utilizing chromatographic techniques together with the information gained by examination of the mutant strains, the fluorescent material has been identified as kynurenine. Of particular interest is the manner of appearance of the fluorescent material in the vicinity of the nuclear membrane of the fat cells.     

EFFECT OF YEAST SEXUAL HORMONES ON ELONGATION OF AVENA COLEOPTILE

Effect of yeast (Saccharomyces cerevisiae) sexual hormones on the elongation of etiolated Avena coleoptile segments was studied. The elongation was promoted by a hormone excreted by cells of mating type a, but not by α hormone excreted by cells of α type. The effect of the former was as great as that of 5 mg/1 indole-3-acetic acid in the first hour of application. The optimal concentration of a hormone was 10 units/ml. Its growth promoting effect was greatly inhibited by an antiauxin, 2,4,6-trichlorophenoxyacetic acid. a Hormone increased cell wall extensibility just as auxin does. Testosterone, β-estradiol, progesterone and ergosterol showed very little effect on the elongation of coleoptile segments.     

A DESEEDED AVENA TEST METHOD FOR SMALL AMOUNTS OF AUXIN AND AUXIN PRECURSORS

The main results presented in this article may be summarized as follows: 1. A test method with deseeded Avena seedlings for small concentrations of auxin and precursors of auxin has been described. 2. This method makes possible quantitative determinations of about ten times as low concentrations of hormone as can be obtained with the standard method, (a) Through an increase in the time of the test, so that nearly all the hormone applied can be utilized. (b) Through an increase in sensitivity of deseeded plants to unilaterally applied small concentrations of hormone. 3. The effect of deseeding in relation to curvature growth is primarily the prevention of auxin regeneration through the removal of the material for auxin synthesis, and in addition the prevention of physiological aging. 4. The mechanism of auxin synthesis in the tip of the coleoptile and the mechanism of auxin regeneration in the new physiological tip have been shown to be identical. 5. The application of the deseeded method is illustrated by determinations of auxin in primary leaves and coleoptile sections of Avena seedlings. 6. The deseeded method has been used as a test method for precursors of auxin obtainable from the coleoptile and from other sources. The method further makes possible a distinction between auxins and these substances which may become activated by the plant. 7. Evidence for the existence of a precursor of auxin in the plant is given (a) indirectly by determinations of the decrease in auxin synthesis in deseeded plants. (b) Directly by its isolation from the plant. 8. Precursors of hetero-auxin are demonstrated; their chemical nature and activation are briefly considered.     

INTRACELLULAR LOCALIZATION OF SAXITOXINS IN THE DINOFLAGELLATE GONYAULAX TAMARENSIS1

The potent neurotoxin saxitoxin, and possibly several of its derivatives, are localized in two types of sites within the marine dinoflagellate Gonyaulax tamarensis Lebour. Immunocytochemical techniques using a polyclonal antibody and epifluorescence microscopy demonstrate toxin localization within the nucleus as well as on the periphery of small granules thought to be starch grains. In the nuclear region, the labelling occurred on or close to the permanently-condensed chromosomes as well as in an area within the two arms of the nucleus in the vicinity of the nucleous. No binding was observed in a closely-related, non-toxic dinoflagellate. Different binding affinities were observed between the nucleus and the grains at high and low antibody dilutions. This may relate to the polyclonal nature of the antiserum and to the presence of multiple toxins within the G. tamarensis isolate studied. Mechanistic interpretations of these labelling patterns remain speculative, especially the localization of the antigen at the outer edge of starch grains, but the distinct labelling in the nuclear region suggests that saxitoxin, with its two positively charged guanidinium groups, may bind to nucleic acids or nuclear proteins in a manner analogous to the polyamines and other cations. The labelling patterns reported here suggest that the saxitoxins may not simply be secondary metabolites but instead could be important compounds involved in the structure and function of the G. tamarensis genome.     

ON THE RELATION BETWEEN GROWTH AND RESPIRATION IN THE AVENA COLEOPTILE

1. The growth of Avena coleoptile sections in sucrose and auxin solutions is inhibited by various substances which are known to act as dehydrogenase inhibitors. 2. Iodoacetate, which is particularly active in this connection, inhibits all growth at a concentration of 5 x 10^–5 M, but produces only a slight inhibition of oxygen uptake. 3. The growth inhibition by iodoacetate is completely removed by malate and fumarate, and to a lesser extent by succinate and pyruvate. 4. These acids themselves increase the effect of auxin on growth and also increase the respiration of the coleoptile sections, but only if auxin is present. 5. When sections have been soaked in malate or fumarate, the addition of auxin considerably increases the total respiration. Further, the concentration range over which this increase takes place parallels that active in promoting growth. 6. The four-carbon acids provide a respiratory system which is part of the chain of growth processes, and which is in some way catalyzed by auxin. It represents a small but variable fraction of the total respiration.