Use of chitin for controlling plant plant-parasitic nematodes

Summary Bean and tomato seedlings, treated with different amounts of ammonia and chitin, and inoculated with the root-knot nematode,Meloidogyne javanica, were reared in two consecutive 35-day growth of shoot and root and the condition of the root systems of both plant species and degree of infection byM. javanica were decreased by increasing amounts of ammonia. Chitin caused a relatively small reduction in gall formation but almost no changes in fresh shoot weights. The effect of chitin on plant growth and nematode attack were also compared in irradiated and non-irradiated soil. In the first cycle galling index of the chitin treated plant was similar to that of untreated plants maintained in the irradiated soil conditions, while in the non-irradiated soil, chitin treatment reduced galling index. In the second cycle, chitin treatment reduced galling index in both irradiated and non-irradiated soils, especially in the latter, where galling index greatly decreased compared with the non-treated plants. Differences in fresh shoot weight between nematode-infected and nematode-free plants amended with chitin were greater under non-irradiated than irradiated conditions, especially in the second cycle. In non-irradiated soil, a higher level of chitinolytic microorganisms, particularly actinomycetes, was found in the second cycle. Contribution from the Agricultural Research Organization (ARO), Bet Dagan, Israel. No. 1520-E, 1985 series.     

The ligand binding domain of the epidermal growth factor receptor is not required for receptor dimerization.

To examine the role of the ligand binding domain of epidermal growth factor receptor in its dimerization, we studied the dimerization of a truncated form of the receptor that resembles v-erbB in that it lacks a ligand binding domain. Receptor dimerization was determined by sedimentation analysis on sucrose density gradients at different concentrations of Triton X-100. At high concentrations of Triton X-100 (0.2%), the truncated receptor occurred as a monomer and displayed low basal autophosphorylation. By contrast, at low concentrations of Triton X-100 (0.01%), it existed as a dimer and exhibited high basal autophosphorylation. The ability of the truncated receptor to dimerize indicates that the ligand binding domain of the epidermal growth factor receptor is not required for receptor dimerization.     

The effects of colchicine and dinitrophenol on the in vivo rates of anaphase A and B in the diatom Surirella

The rates of chromosome-to-pole movement (anaphase A) and pole-pole separation (anaphase B) in vivo were measured in the pennate diatom Surirella, using differential interference contrast (DIC) light microscopy. In control cells, the rate of anaphase A is 1.6 +/- 0.6 micron/min, the rate of anaphase B is 2.3 +/- 0.3 micron/min, and the extent of anaphase B is 26.7 +/- 9.7% of metaphase spindle length. Colchicine was added to metaphase cells in order to inhibit any further addition of microtubule (MT) subunits onto the spindle. Colchicine, which does not break down the well-ordered Surirella central spindle, caused no significant change in the rate of anaphase A (1.3 +/- 0.3 micron/min) while it significantly decreased both the rate of anaphase B (1.2 +/- 0.4 micron/min) and the extent of anaphase B (14.8 +/- 8.3% of metaphase spindle length). Surirella cells were also treated with the metabolic inhibitor 2-4-dinitrophenol (DNP) in order to test the effects of energy depletion on anaphase. When DNP was added early in anaphase A, prior to the completion of sister chromosome separation, anaphase A was inhibited. When DNP was added after initiation of sister chromosome separation, anaphase A continued to completion, although at a lower rate than control cells (0.5 +/- 0.2 micron/min). Anaphase B was completely inhibited by DNP, but upon recovery from DNP resumed at a normal rate (2.2 +/- 0.5 micron/min) and progressed to a slightly larger than normal extent (44.0 +/- 13.0% of metaphase length).(ABSTRACT TRUNCATED AT 250 WORDS)     

Changes in tertiary structure accompanying a single base change in transfer RNA. Proton magnetic resonance and aminoacylation studies of Escherichia coli tRNAMet f1 and tRNAMet f3 and their spin-labeled (s4U8) derivatives.

The properties of Escherichia coli tRNAMet f1 and tRNAMet f3 that differ by only one base change, m7G to A at position 47, have been compared structurally by proton magnetic resonance and functionally by the aminoacylation reaction. The NMR spectra of the two tRNA species in the region between 0 and 4 ppm below 4,4-dimethyl-4-silapentane-1-sulfonic acid (DSS) (methyl and methylene region) were the same except for the absence of the lowest field peak at 3.8 ppm in tRNAMet f3, thus unequivocally identifying this resonance at the methyl group of m7G47 of tRNAMet f1. The same resonance disappears in tRNAMet f1 spin-labeled at s4U8 and reappears in the diamagnetic reduced spin-labeled tRNAMet f1 from which the average distance between the spin-label and the methyl protons of m7G is estimated to be less than 15 A. The proximity of m7G47 but not T55 to s4U8 in the structure of E. coli tRNAMet f1 in solution is consistant with the crystallographic model for yeast tRNAPhe. A spectral comparison of the hydrogen-bond regions (11-14 ppm below DSS) of tRNAMet f1 and tRNAMet f3 reveals major shifts of four resonances previously assigned to tertiary hydrogen bonds. Of the four, the one at lowest field (14.8 ppm) had been assigned by chemical modification to the tertiary (s4U8-A14) hydrogen bond and the one at 13.3 ppm had been tentatively assigned to the tertiary hydrogen bond G23-m7G47 of the 13-23-47 triple. A more positive assignment of the G23-m7G47 at 13.3 ppm could be made from the additional evidence that this resonance, which was first observed in the difference spectrum between spin-labeled tRNAMet f1 and its reduced form, is the only one missing in the analogous difference spectrum of tRNAMet f3. At low ionic strength and in the absence of magnesium ions, the differences in the hydrogen-bonded region of the NMR spectra of tRNAMet f1 and tRNAMet f3 are much greater than in the presence of magnesium ions. The optimal magnesium concentration required for maximal initial velocities is also higher for tRNAMet f3 than for tRNAMet f1. The perturbation caused by the spin-label in destabilizing hydrogen bonds in the region between 13 and 14 ppm is greater for tRNAMet f3 than tRNAMet f1 but the distance relations for the hydrogen bonds in the region between 12 and 13 ppm (the major paramagnetic perturbations) are conserved in the two species. The disruption of one hydrogen bond relative to native tRNAMet f1 either by spin-labeling (s4U8-A14) or by substitution of m7G by A in tRNAMet f3 has little effect on the aminoacyl acceptor activity or the velocity of the aminoacylation reaction at optimal magnesium concentration, but the absence of both tertiary hydrogen bonds in the augmented D-helix region in the spin-labeled tRNAMet f3 results in approximately 60% reduction both in acceptance activity and in initial velocity of the aminoacylation reaction.     

Aldehyde dehydrogenase from human erythrocytes: structural relationship to the liver cytosolic isozyme

Human red cell aldehyde dehydrogenase (ALDH) resembles the liver cytosolic isozyme in numerous physicochemical properties. This study was undertaken to establish the structural relationship between the erythrocyte and liver ALDH isozymes. The purified red cell ALDH was S-(14C)-carboxymethylated, and cleaved with trypsin. The tryptic digest was fractionated using Sephadex and reversed-phase chromatography. All peptides analyzed were identified within the liver cytosolic enzyme structure. In each case the sequence obtained corresponds exactly to a segment from the human liver cytosolic ALDH. Thus, the erythrocyte enzyme, by virtue of its chemical and structural identity with the liver cytosolic enzyme, may serve as a suitable peripheral enzyme model to understand the cause and mechanism of alcohol abuse-related changes in liver cytosolic ALDH that has been found to be reduced in alcoholics.