David M. Bonner

Note on Induction of Flowering in Xanthium

ting agent alld possibly by better pene tration owing to the presence of the oillike estere The combination spray described in this paper has been formulated for use in sugar-cane fields. Because of the great similarity of the plants, it should also be useful in corn. Tests have proved that it can be used in fields of growing corn in which a wide variety of weeds, including grasses, have been completely killed. It has also proved effective as a pre-emerZ gerlce spray in corn and sugar-cane fields. It seems that pre-emergellce treatment followed by two or three sprays in the growing crop may provide a solution to weed problems in these two major food

Relation of Environment and of the Physical Properties of Synthetic Growth Substances to the Growth Reaction

1. It is concluded that the acid curvature in the pea test is due to a greater growth of the cut surface than of the intact surface. This is explained as due to a higher concentration of active auxin on the cut surface, caused by a measurable decrease of the internal pH of the cut surface, when split pea sections are placed in acid buffers. 2. A correlation is found between the dissociation curves and the activities at different internal pHs of cis-cinnamic acid and phenylacetic acid. 3. By correcting for difference in pK, so that only equimolar concentrations of the free acid are compared, it is found that cis-cinnamic acid possesses the same activity as indole (3) acetic acid in the pea test. The activity of phenylacetic acid, although enhanced, was not so high as that of indole (3) acetic acid. 4. By pretreating pea sections with phenylbutyric acid and correcting for difference in pK when possible, the following compounds are found to possess molar activities equal to that of indole (3) acetic acid in the pea test: indole (3) propionic acid, indole (3) butyric acid, napthaleneacetic acid, anthraceneacetic acid, and cis-cinnamic acid. The activities of phenylacetic acid and of indole(3) valeric acid, although increased, are not brought to that of indole (3) acetic acid. 5. It is suggested that compounds possessing the essential molecular structure probably all have the same activity in the pH dependent, and stoichiometric growth reaction, and that the differences in their observed activities are due to differences in activities in secondary processes.

Purification and partial characterization of tryptophan synthetase from Neurospora crassa

Abstract A method is described for the purification of tryptophan synthetase ( l -serine hydrolyase (assing indole), EC 4.21.20) from Neurospora crassa . 1. 1. Specific activities of 120–250 units/mg protein have been observed in preparations judged to be homogeneous on the basis of ultracentrifugal and electrophoretic criteria. 2. 2. Storage of the purified material at —70° after quick-freezing in liquid nitrogen was found to cause no detectable change in ultracentrifugal properties despite reduction in enzymic activity. In addition, purified material having two widely different activities was shown to possess identical immunochemical properties. 3. 3. The molecular weight of the enzyme is (1.1 ± 0.1) × 10 5 as determined by the Archibald method. 4. 4. The s 20, w 0 was found to be 6.2 ± 0.2 S. 5. 5. The molar frictional ratio of 1.28 was determined from the experimental and calculated molar frictional coefficients.

Tryptophan synthetase in Bacillus subtilis: Effects of high potassium ion concentration on a two component enzyme

The three reactions of the enzyme tryptophan synthetase have been demonstrated in extracts from Bacillus subtilis. The following characteristics of this enzyme have been shown in these studies. 1. 1. The activity in Reaction 2, the condensation of indole and serine to form tryptophan, is stimulated by K+. Na+ is somewhat less stimulatory, while NH4+ is inhibitory. 2. 2. Thermal inactivation of Reaction 2 activity follows apparent second-order kinetics. The stability increases with increasing K+ and appears to become first order in the presence of 1.0 M KCl. 3. 3. The conversion of indole 3-glycerol phosphate to indole, Reaction 3, shows greater thermal stability than Reaction 2 and also gives a biphasic heat inactivation curve. Reaction 1, the condensation of indole 3-glycerol phosphate and serine to form tryptophan, is the most thermostable of the three reactions under conditions of low K+ concentration. 4. 4. Two components can be separated on Sephadex G-75, one with activity in Reaction 2, and a second fraction which in combination with the Reaction 2 peak shows activity in Reaction 1. 5. 5. Two effects of K+ have been demostrated, the major one on Reaction 2, and a minor one involving the other two reactions. K+ stimulates Reaction 1 activity with parallel decrease in the Reaction 3 activity. The significance to these findings is discussed and possible explanations for the salt effect presented.

Genetic determination of the antigenic specificity of tryptophan synthetase

Rabbit antiserum was obtained against the purified enzyme, tryptophan synthetase, from the fungus Neurospora crassa . With quantitative serological methods it was possible to demonstrate the gene products of a large class of mutant strains (CRM − , td mutants) which cross-react with the non-neutralizing fraction of the antiserum. Differences were also uncovered in a second class of mutant strains (CRM + , td mutants) hitherto considered antigenically identical. The results have shown a relationship between the position of the lesion within the td locus and the nature of the cross-reacting protein present in the CRM~ extract.

Complementation between tryptophan synthetase mutants of Neurospora crassa

Abstract Studies of complementation in vivo and in vitro in the tryptophan synthetase system of Neurospora have shown the following: 1. The enzymes produced by heterokaryons between allelic tryptophan synthetase ( l -serine hydro-lyase (adding indole), EC 4.2.1.20) mutants of Neurospora are not identical to the wild-type enzyme in terms of their affinities for substrates, cofactor nor in their thermostabilities; 2. complementation patterns in vitro and in vivo are not identical; 3. an increase in enzyme activity attained by mixing the partially purified extracts results from the formation of a new enzyme molecule (enzyme in vitro ) as revealed by heat inactivation studies; 4. the thermostability of the enzyme in vitro is different from that of wild-type enzyme. The thermostabilities of enzymes in vitro are similar but not identical to that of corresponding heterokaryon enzymes. The significance of these findings is discussed with respect to the possible mechanism of complementation.

Activity of the Potassium Salt of Indole(3)Acetic Acid in the Avena Test

The results obtained by various workers which seem to show a greater activity of the potassium salt of indole(3)acetic acid in comparison with that of the free acid were tested. In several experiments it was found that the three substances indole(3)acetic acid, potassium indole(3)acetate, and sodium indole(3)acetate possessed similar activities when their equimolar solutions, buffered at the same pH, were given the Avena test. Thus, as would be expected from theoretical considerations, these three substances, if buffered at the same pH, possess the same activity. In the case of the unbuffered solutions it is suggested that the difference in activity may be due to a pH effect.

The use of mutants in the study of metabolism

The metabolic, especially the biosynthetic, mechanisms underlying the dramatic phenomenon of cellular growth have held a persistent fascination for biologists and biochemists alike. So varied and numerous are the synthetic reactions required for growth that their integration in the economy of the cell is remarkable indeed. It has long been realized that the necessary regulation of cellular activities depends, at least to an important degree, on the genetic apparatus of the cell. However, detailed demonstrations of the interrelation between the genetic apparatus and well defined biochemical activities have appeared only in recent years. As a notable consequence of these investigations, potent methods have become available for the analysis of various metabolic processes, particularly of biosynthetic pathways. Simultaneously with this development of the methods of biochemical genetics, substantial strides have been made in the use of enzyme and isotope techniques in studies of biosynthesis. While the present discussion is primarily concerned with methods contributed by the field of biochemical genetics, it will be shown that these methods lead to conclusions that are consistent with, and complementary to, those derived from isotope and enzyme studies.