O3 Tolerance and the Ascorbate-Dependent H2O2 Decomposing System in Chloroplasts

The relationship between O₃ tolerance and the chloroplast H₂O₂scavenging system (PS I     

Inhibition of Photosynthesis by Sulfite in Mesophyll Protoplasts Isolated from Vicia faba L. in Relation to Intracellular Sulfite Accumulation

Inhibition of photosynthesis by Na₂SO₃ in mesophyll protoplastsisolated from Vicia faba leaves and uptake of sulfite by theprotoplasts were examined at various pH values of the incubationmedium containing Na₂SO₃. As the pH of the incubation mediumlowered, the rate of photosynthesis in the protoplasts decreasedand the amount of sulfite taken up by the protoplasts increased.Most of sulfite accumulated in the protoplasts was not metabolizedduring the dark incubation, as measured with an ion chromatograph.Photosynthetic O₂ evolution by the chloroplasts isolated fromVicia mesophyll protoplasts was inhibited by exogenously-appliedNa₂SO₃ over pH region examined (7.4–9.0). The sulfiteconcentration required for a half inhibition of photosynthesisby the isolated chloroplasts was similar to the intracellularsulfite level required for that by the protoplasts. These resultsindicate that the intracellular sulfite accumulated in the protoplastsin an unmetabolized state is responsible for the inhibitionof protoplast photosynthesis. (Received January 24, 1985; Accepted May 29, 1985)     

Direct Observation of Reversible and Irreversible Stomatal Responses of Attached Sunflower Leaves to SO(2)

The effects of SO₂ on stomatal aperture of attached sunflower leaves were observed with a remote-control light microscope system that permitted continuous observation of stomatal responses over periods of several hours. The relationship between actual stomatal aperture and stomatal conductance, measured with a porometer, also was examined on leaves before and after exposure to SO₂.

A distinction between uninjured and injured regions was clearly visible on leaves after exposure to 1.5 microliters per liter SO₂ for less than an hour. During the exposure, the mean value of apertures for many stomata, which indicates stomatal conductance and transpiration rate, tended to decrease simultaneously in the uninjured and injured regions. However, the rate of decrease in the injured region was slower than that in the uninjured region because of a transient opening induced by water-soaking in the injured region. The transient opening was less common in stomata near veins and veinlets.

There was a good correlation between pore width and stomatal conductance measured with a porometer before exposure to SO₂. This correlation continued in leaves exposed to SO₂ until visible, irreversible injury occurred, but then it disappeared.

The results of these experiments indicate the necessity of continuous observation of individual stomata under the microscope to understand the effects of air pollutants such as SO₂ on stomatal behavior.

     

Light Activation of NADP-Malate Dehydrogenase in Guard Cell Protoplasts from Vicia faba L

Light-induced swelling of guard cell protoplasts (GCP) from Vicia faba was accompanied by increases in content of K⁺ and malate. DCMU inhibited the increase of K⁺ and malate, and consequently swelling.

Effect of light on the activity of selected enzymes that take part in malate formation was studied. When isolated GCP were illuminated, NADP-malate dehydrogenase (NADP-MDH) was activated, and the activity reached a maximum within 5 minutes. The enzyme activity underwent 5- to 6-fold increase in the light. Upon turning off the light, the enzyme was inactivated in 5 minutes NAD-MDH and phosphoenolpyruvate carboxylase (PEPC) were not influenced by light. The rapid light activation of NADP-MDH was inhibited by DCMU, suggesting that the enzyme was activated by reductants from the linear electron transport in chloroplasts. An enzyme localization study by differential centrifugation indicates that NADP-MDH is located in the chloroplasts, NAD-MDH in the cytosol and mitochondria, and PEPC in the cytosol. After light activation, the activity of NADP-MDH in guard cells was 10 times that in mesophyll cells on a chlorophyll basis. The physiological significance of light-dependent activation of NADP-MDH in guard cells is discussed in relation to stomatal movement.

     

Immigration of the brown planthopper, Nilaparvata lugens, exhibiting various responses to density in relation to wing morphism

Considerable inherent variations in the relation between macropterous and brachypterous wing forms, and nymphal density were found in field populations of the brown planthopper, Nilaparvata lugens Stål (Homoptera: Delphacidae), collected from various locations in Japan. When compared under uniform laboratory rearing conditions, most of the female populations exhibited higher ratios of macropters with increasing nymphal density, but some showed extremely high proportion of brachypters and the others were highly macropterous, over broad ranges of density. These results indicate the possibility that the planthoppers in Japan, which are known not to persist in winter, are derived from different migration sources.About ten generations of successive selection for brachyptery from a population showing usual density-dependent wing morphism generated populations similar to highly brachypterous ones mentioned above. Genetic analysis of the inheritance of wing morphism revealed that brachyptery in the females was controlled by a single pair of dominant alleles. However, in the males wing forms did not segregate so clearly in the crossing experiments. This suggests that wing morphism in N. lugens in under sex-limited inheritance.

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Einwanderung von Nilaparvata lugens mit unterscheidlicher Reaktion auf Populationsdischte bei der Flügelausbildung

Zusammenfassung In Feldpopulationen von Nilaparvata lugens Stål., welche in verschiedenen Regionen Japans gesammelt wurden, bestand in der Beziehung zwischen makropteren bzw. brachypteren Flügelformen und der Larvendichte eine beträchtliche Variation. Unter einheitlichen Zuchtbedingungen im Laboratorium stieg der Makropterenanteil bei den meisten Weibchenpopulationen mit steigender Temperatur; bei einigen Populationen hingegen war entweder der Brachypterenanteil oder der Makropterenanteil extrem hoch und zwar über weite Dichtebereiche. Dies deutet auf die Möglichkeit hin, dass die Zikade in Japan, wo sie bekanntlich nicht überwintert, jeweils aus verschiedenen Quellen einwandert.Wenn eine Population mit der üblichen dichteabhängigen Flügelausbildung 10 Generationen lang auf Brachypterie selektioniert wurde, entstanden Populationen, die den erwähnten hochbrachypteren Populationen aus dem Feld glichen. Die genetische Analyse der Vererbung der Brachypterie ergab, dass bei Weibchen ein einzelnes dominantes Allel verantwortlich ist. Bei Männchen dagegen trennten sich bei Kreuzungsexperimenten die Flügelformen nicht so klar. Dies deuted auf Unterschiede zwischen den Geschlechtern bei der Vererbung der Flügelformen.

     

The heterogeneity of human fibroblasts as determined from the effects of hydrocortisone on cell growth and specific dexamethasone binding

To elucidate the heterogeneity of human fibroblasts from lung and skin, the effects of hydrocortisone on cell proliferation and the specific dexamethasone binding to cells were studied. Hydrocortisone at physiological concentrations stimulated the proliferation in three strains of human fetal lung fibroblasts and inhibited it in two strains. There are two kinds of fibroblasts in the human fetal lung in addition to the human skin fibroblasts reported previously. Dexamethasone-binding experiments showed that human fibroblasts may be classified into two groups with respect to the dissociation constant (Kd) of the binding reaction. The heterogeneity of human fibroblasts shown by Kd could not be correlated to classification on the basis of the effects of hydrocortisone on cell proliferation. The differences in Kd for the binding reactions suggest differences in donor tissues from which human fibroblasts are derived.     

Studies on the metabolism of unsaturated fatty acids. XVI. Purification and general properties of 2,4-dienoyl-CoA reductase from Candida lipolytica

2,4-Dienoyl-CoA reductase has been purified to homogeneity from Candida lipolytica cultivated in the presence of linoleic acid. The native enzyme had a molecular weight close to 360,000 as estimated by gel filtration on Sepharose CL-4B, whereas the subunit molecular weight estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis was 33,000. The purified 2,4-dienoyl-CoA reductase from C. lipolytica gave a single precipitin line with antibodies raised against the purified enzyme from C. lipolytica. The general properties of the 2,4-dienyl-CoA reductase from C. lipolytica were examined. The enzyme had optimal pH at 6.5 and was inactivated by heat treatment at 50 degrees C for 10 min. trans-2,trans-4-Octadienoyl-CoA was the most active substrate of the dienoyl-CoA esters examined.     

Aspartate aminotransferase isozymes from rabbit liver. Purification and properties

Cytosolic and mitochondrial isozymes of aspartate aminotransferase (L-aspartate:2-oxoglutarate aminotransferase [EC 2.6.1.1] ) were purified to homogeneity from rabbit liver. The rabbit liver isozymes were closely similar to the corresponding isozymes from other sources, including human heart, pig heart, chicken heart, and rat liver, in their molecular weights, absorption spectra, amino acid compositions, isoelectric points, and Michaelis constants for the substrates. The NH2-terminal amino acid sequences of rabbit liver isozymes were identified up to 30 residues, and showed some differences from those of the corresponding isozymes obtained from other animals so far studied.     

Amino acid sequences of the two kinds of regulatory light chains of adductor smooth muscle myosin from Patinopecten yessoensis

Smooth muscle myosin from scallop (Patinopecten yessoensis) adductor muscle contains two kinds of regulatory light chains (regulatory light chains a and b), and myosin having regulatory light chain a is suggested to be suitable for inducing "catch contraction" rather than myosin having regulatory light chain b (Kondo, S. & Morita, F. (1981) J. Biochem. 90, 673-681). The amino acid sequences of these two light chains were determined and compared. Regulatory light chain a consists of 161 amino acid residues, while regulatory light chain b consist of 156 amino acid residues. Amino acid substitutions and insertions were found only in the N-terminal regions of the sequences. The structural difference between the two light chains may contribute to the functional difference between myosins having regulatory light chains a and b.     

Molecular cloning and nucleotide sequence of the cDNA for rat peroxisomal enoyl-CoA: hydratase-3-hydroxyacyl-CoA dehydrogenase bifunctional enzyme

For the studies on the mechanism of induction of peroxisomal beta-oxidation enzymes and biogenesis of the organelle, we have isolated cDNA clones for rat peroxisomal enoyl-CoA: hydratase-3-hydroxyacyl-CoA dehydrogenase bifunctional enzyme. On blotting experiments with liver RNA, the cDNAs hybridized to a 3.0-kilobase RNA which was increased 5-7-fold by the administration of di-(2-ethylhexyl)phthalate to rats. Nucleotide sequencing was carried out for four cloned cDNAs and one obtained by a primer extension method. By overlapping these sequences with each other, we identified 20 nucleotides of 5'-noncoding, 2,166 nucleotides of coding, and 910 nucleotides of 3'-noncoding regions. The deduced amino acid sequence of the enzyme is composed of 722 residues, and the composition agrees with that of the protein data. The sequence was confirmed by the amino acid compositions and sequence analyses of some of the tryptic peptides. The molecular weight of the mature enzyme is calculated to be 78,511 from the predicted amino acid sequence. The enzyme has no terminal peptide extension as a signal for translocation into peroxisomes.