Characterization of a stress-induced,developmentally regulated gene family from soybean

We describe a family of stress-induced, developmentally regulated soybean genes for which cDNAs have been obtained from two different cultivars (Glycine max cv. Mandarin and Glycine max cv. Williams). The mRNAs corresponding to these cDNAs, called SAM22 and H4, respectively, accumulate predominantly in the roots of soybean seedlings but are present at high levels in the roots and leaves of mature plants. SAM22 accumulation is especially dramatic in senescent leaves. In addition, SAM22 accumulation can be induced in young leaves by wounding or by transpiration-mediated uptake of salicylic acid, methyl viologen, fungal elicitor, hydrogen peroxide or sodium phosphate (pH 6.9). Taken together, these data indicate that the genes corresponding to SAM22 and H4 are induced by various stresses and developmental cues. Southern blot analysis indicates that multiple copies of sequences related to SAM22 exist in the soybean genome. We also show that the nucleotide sequences of the cDNAs corresponding to SAM22 and H4 are 86% identical at the nucleotide level to each other and 70% identical at the amino acid level to the disease resistance response proteins of Pisum sativum.     

Anticataleptic potencies of glutamate-antagonists

Summary The anticataleptic effects of non-competitive and competitive NMDA antagonists as well as those of an agonist at the allosteric glycine binding site of the NMDA receptor were tested in the catalepsy model. Some of these drugs were further tested in a reaction time task demanding rapid locomotor initiation. The results show that the non-competitive NMDA antagonists dizocilpine and memantine as well as the competitive antagonists CGP 39551, CGP 37849 and CPPene antagonized dopamine D2 receptor mediated catalepsy induced by haloperidol. D-cycloserine, a partial glycine agonist per se had no effects, but it enhanced the anticataleptic effects of dizocilpine when coadministered. However, the effects of CGP 37849 were abolished. Dopamine D1 receptor mediated catalepsy induced by SCH 23390 was antagonized by dizocilpine, memantine, CPPene, but not by CGP 37849. In the reaction time task dizocilpine, memantine and CGP 37849 were tested for their anti-akinetic and anti-bradykinetic potencies. All these compounds improved haloperidolinduced slowing of reaction time. However, they acted differentially on haloperidol-induced slowing of movement execution and decreased initial acceleration. Thus, antagonists at the NMDA receptor may have a therapeutic potential in the treatment of Parkinson's disease. Their potency can be manipulated specifically at the glycine binding site.     

Glycinebetaine biosynthesis and its control in detached secondary leaves of spinach

In secondary leaves from spinach plants pretreated in vermiculite for 24 h with 300 mM NaCl, glycinebetaine accumulated at a rate of circa 0.16 mol 100 g^-1 Chl d^-1 (2 mol g^-1 FW d^-1), about three times the rate of control plants. The soluble carbohydrate and free amino acid contents did not increase significantly following salinisation until after 4 d when the relative growth rate also decreased. Leaf proline levels remained very low throughout the experimental period. K⁺ on a tissue water basis remained constant at 200 mM while Cl^- and Na⁺ levels increased linearly to reach 175 and 100 mM respectively after 5 d of saline treatment. The osmotic pressure of leaf tissue also increased from 300 to 500 mosmol kg^-1. These experimental conditions were considered suitable to study glycinebetaine biosynthesis and its induction by salinity in the absence of marked growth inhibition or metabolic disturbance. Radioactive labelled [¹⁴C]serine, ethanolamine and choline (all 1 mol, 13.3 MBq in 10 l) were fed to detached secondary leaves via the petiole 24 h after the exposure of plants to salt. The rate of isotope incorporation into water soluble products, lipids and residue was measured over a further 24 h. The major metabolic fate of exogenous [¹⁴C]choline and [¹⁴C]ethanolamine was incorporation into glycinebetaine while less ¹⁴C-label was found in phosphatidyl choline and phosphatidyl ethanolamine. Incorporation rates were identical in control and salinised leaves and were adequate to account for observed values of glycinebetaine accumulation previously reported in spinach. In contrast the labelling of glycinebetaine from [¹⁴C]serine was twice as great in salinated plants as in the controls. These results, together with short term labelling experiment with [¹⁴C]ethanolamine using leaf slices, were consistent with the formation of glycinebetaine via serine, ethanolamine and its methylated derivatives to choline with some control being exerted at the serine level. However a flux through the phosphorylated intermediates is not excluded.From a consideration of these results and the published data on barley subjected to water stress (Hanson and Scott, 1980 Plant Physiol. 66, 342–348) there appear to be significant differences in the biosynthetic pathways in spinach and barley.Abbreviations BHT butylated hydroxytoluerte (2,6-di-tert-butyl-4-methylphenol) - C₁ one-carbon fragment - 1,2DG diglyceride moiety - DW day weight - MCW methanol-chloroform-water (12:5:1, by vol.) - PA phosphatidic acid - PC phosphatidyl choline - PMME phosphatidyl monomethylethanolamine - PDME phosphatidyl dimethylethanolamine - PE phosphatidyl ethanolamine - PPO 2,5-diphenyloxazole - POPOP 1,4-bis(5-phenyloxazoyl) benzene     

The Relationship Between Soil Populations of Meloidogyne incognita and Yield Reduction of Soybean in the Coastal Plain

In a replicated field plot experiment, the population density of Meloidogyne incognita was monitored biweekly through the overwintering period (December through April) between soybean crops. The population survived as second-stage juveniles whose numbers remained stable through the winter months and did not decline until February. The yields of plots planted with a M. incognita susceptible cultivar were negatively correlated with the numbers of juveniles recovered at all preplanting sampling dates. In the mid-winter period (December through February), a regression equation describing the relationship predicted a yield reduction (slope) equivalent to 5.36 kg/ha for each juvenile in a 10-cm³ soil sample. In two subsequent field experiments, conducted in different sites and years, mid-winter (November) sampling gave yield reduction predictions of 4.65 and 6.69 kg/ha. Tests of the null hypothesis gave no evidence to indicate that the three slopes differed (P = 0.05). A regression analysis of combined data from the three experiments determined a mid-winter predictive yield reduction of 5.31 kg/ha for each juvenile in the 10-cm³ sample. As the sampling time approached the planting date, there were changes in the predictive yield reductions due to each juvenile in a sample. These are best described by the equation, $\widehat{\gamma }$ (yield loss) = 54.47 - 0.67X + 0.0023X², where X equals the days remaining between sampling and planting. Soil sampling should be performed during mid-winter (November through January) for the most reliable prediction of soybean yield loss.     

Selective Stimulation of Neurotransmitter Release from Chick Retina by Kainic and Glutamic Acids

The excitatory action of kainic and glutamic acids in chick whole retina was demonstrated as an immediate stimulation of the release of labeled gamma-aminobutyric acid (GABA) and glycine in a superfusion system. This stimulatory effect was 3-10 times greater than that produced by a depolarizing K+ concentration; in addition, it was independent of Ca2+ in the medium, but notably inhibited when Na+ was omitted from the medium. Under identical experimental conditions, neither kainic nor glutamic acid had any effect on the release of labeled dopamine or alpha-aminoisobutyric acid, thus indicating that their effect is not unspecific or due to cell damage. Similar although less marked stimulation of labeled GABA and glycine release by kainic acid was obtained in subcellular retinal fractions, particularly in fraction P1, which contained photoreceptor terminals and outer segments. This stimulation was also Ca2+ independent and greatly reduced when Na+ was omitted from the medium. It is suggested that the stimulation of GABA release by kainic and glutamic acids is probably due to a Na+-dependent, carrier-mediated mechanism that responds to the entry of Na+ produced by the interaction of glutamic and kainic acids with retinal membranes. In cortical or striatal slices from mouse brain, these acids had a negligible stimulatory effect on GABA and dopamine release.     

Damage and Reproductive Potentials of Pratylenchus brachyurus and P. penetrans on soybean

Damage and reproductive potentials of Pratylenchus brachyurus and P. penetrans on soybean, Glycine max, cvs. Essex, Forrest, and Lee 68, were determined in microplot tests. Cultivar Essex was generally tolerant to P. brachyurus. Yield of Forrest was suppressed linearly with increasing P_i''s in the sandy soil (r = -0.92) and loamy sand soil (r = -0.99). Low to moderate P_i''s in the sandy clay loam gave an increase in yields as compared to plants without nematodes. Yield was not affected by this nematode in muck. Lee 68 was very sensitive to P. penetrans in microplots. Yield vs. P_i was fitted by a quadratic model (r = 0.82) with yield decreasing sharply as P_i''s were increased. The reproduction of both species decreased with increases in P_i. Lee 68 was a good host for P. penetrans, whereas Essex and Forrest were fair to poor hosts for P. brachyurus.     

Determination of the Equilibrium Dissociation Constants and Number of Glycine Binding Sites in Several Areas of the Rat Central Nervous System, Using a Sodium-Independent System

Parameters affecting the binding of [3H]glycine to membrane fractions isolated from the cerebral cortex, midbrain, cerebellum, medulla oblongata, and spinal cord of the rat were investigated in a Na+-free medium. A [3H]glycine binding assay was established in which the binding was specific, saturable, pH-sensitive, and reversible. Conditions were chosen in an effort to minimize binding to glycine uptake sites. From data on specific [3H]glycine binding Scatchard plots were prepared and the KD and Bmax values were calculated. Two glycine binding sites (high and low affinity) were identified only in the medulla (KD: 44, 211 nM; Bmax: 361, 1076 fmol/mg protein) and spinal cord (KD: 19, 104 nM; Bmax: 105, 486 fmol/mg protein). The ranges of the KD and Bmax values for the other three areas studied were 59 to 144 nM and 882 to 3401 fmol/mg protein, respectively. When the glycine content of each area, expressed as fmol/neuron, was plotted against the respective KD (high affinity), a negative correlation was found (r = --0.90; p less than 0.05). A similar negative correlation was found between the glycine content and Bmax (r = --0.88; p less than 0.05). Hill plots indicated a slope of essentially 1.0 for all areas. GABA, taurine, strychnine, diazepam, bicuculline, and imipramine had little or no effect on [3H]glycine binding.     

Identification of Strychnine Binding Sites in the Rat Retina

Abstract: [³H]Strychnine specifically binds to membrane fractions isolated from rat retinae. The binding is saturable, with an apparent dissociation constant, K _D, of 14.3 × 10⁻⁹ M and 205 fmol bound/mg protein. Specific binding is time-dependent and proportional to protein concentration. Glycine and taurine are equally potent inhibitors of [³H]strychnine binding ( K _i= 4 × 10⁻⁵ M); no other amino acids endogenously present in the retina inhibited [³H]strychnine binding.     

The effect of silicon on the manganese nutrition of soybeans (Glycine max (L.) Merrill)

Summary Silicon during the early vegetative stage did not affect the oven dry weight of any of the various tissues of the soybean plant. Silicon did, however, decrease the Mn concentration in the youngest fully mature leaf at intermediate levels of Mn. This effect did not occur at the lowest or highest Mn levels. Deficiency and toxicity symptoms were moderated to a slight degree by Si except at the highest level of Mn.     

Interactions among leaf photosynthetic rates,flowering and pod set in soybeans

The seasonal maximum in photosynthetic CO₂ exchange rate (CER) and the cessation of leaf expansion in soybeans (Glycine max (L.) Merr) accompany fruiting under normal agricultural conditions. To investigate whether these phenomena were obligatively tied together, we caused early flowering of long-season varieties by imposing artificial short-day treatments. Comparisons of CER and leaf area between vegetative (long-day treatment) and fruiting (short-day treatment) plants of long-season cultivar confirmed the relationship of these phenomena. The same comparisons made between a long-season and a short-season cultivar, both at the same daylength, also confirmed the relationship.