Light Activation of Pyruvate,Pi Dikinase and NADP-Malate Dehydrogenase in Mesophyll Protoplasts of Maize : Effect of DCMU, Antimycin A, CCCP, and Phlorizin

Pyruvate,Pi dikinase (PPDK, EC 2.7.9.1) and NADP-malate dehydrogenase (MDH, EC 1.1.1.82) were activated in the light and inactivated following a dark treatment in mesophyll protoplasts of maize. DCMU (up to 33 micromolar), an inhibitor of noncyclic electron transport, inhibited activation of MDH much more strongly than it did PPDK. Antimycin A (6.6-33 micromolar), an inhibitor of cyclic photophosphorylation, inhibited the activation of PPDK (up to 61%), but had little or no effect on activation of MDH. Carbonyl cyanide m-chlorophenylhydrazone (0.2-2 micromolar) and nigericin (0.4 micromolar), uncouplers of photophosphorylation, inhibited activation of PPDK while stimulating the activation of MDH. Phlorizin (0.33-1.7 millimolar), an inhibitor of the coupling factor for ATP synthesis, strongly inhibited activation of PPDK but only slightly effected light activation of MDH. These results suggest that noncyclic electron flow is required for activation of NADP-MDH and that photophosphorylation is required for activation of PPDK.     

Refined genetic analysis of the region II che mutants in Salmonella typhimurium

Summary From a detailed complementation analysis of the region II che mutants of Salmonella typhimurium, we have located five che genes, cheA, cheW, cheR, cheB, and cheY. We have shown that corrections are required in the previous assignment of the mutations in four strains: both SL2514 and SL2515 which have been reported to be cheY mutants are cheR mutants, SL2539 is not a cheA but a cheW mutant, and ST171 which has been reported to be a cheZ mutant is a double mutant with defects in both cheA and cheB. Since ST171 is the only cheZ mutant so far isolated, the idea that the cheZ gene might play an essential role in chemotaxis in S. typhimurium as in Escherichia coli has lost its experimental basis. Furthermore, a number of deletion mutants in region II resulting from the excision of Tn10 have been isolated and analysed. From these experiments, we propose that the gene order in region II is flaK-flaE-motA-motB-cheA-cheW-cheR-cheB-cheY-flaM-flaC, which is identical with that in E. coli.     

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.     

A Study on Erythrocyte Membrane Plasmalogen in Myotonic Dystrophy

Phospholipid classes that included plasmalogens of erythrocyte membranes in seven myotonic dystrophy (MyD) patients and seven normal controls were analyzed by HPLC. No significant difference in phospholipid classes was found between patients with MyD and normal controls, but there was a visible difference in peak profiles of compounds of the phosphatidylethanolamine class. In the study of plasmalogens, we used two preparation methods: exposure to HCl and deacylation with mild alkaline. The area ratio of the plasmalogen form to the diacyl form in the phosphatidylethanolamine class of MyD erythrocyte membranes was significantly lower than that of normal controls. Fatty acid analyses showed that fatty acids of both phosphatidylethanolamine subclasses have less unsaturation in MyD.     

A photosystem other than PS370 also mediates the negative phototaxis of Halobacterium halobium

Abstract It was found that a photorepellent system other than photosystem 370 (PS370) also controls the behavior of Halobacterium halobium . Both the dependence of background illumination and wavelength where the response showed maximum action distinguished that photosystem from PS370 whose photoreceptor pigment is thought to be an intermediate of s-rhodopsin (sR). A mutant strain that has no detectable activity in PS370 and in photoattractant response was isolated. This mutant strain showed the repellent response due to the new photosystem.     

Social and reproductive behavior of three mouthbrooding cardinalfishes,Apogon doederleini,A. niger and A. notatus

Synopsis Social and reproductive behavior of three paternal mouthbrooding cardinalfishes (Apogonidae) were investigated in the shallow marine waters of Shirahama, Japan. The solitary species Apogon doederleini and A. niger bred in transient pairs, in which a male and female associated for only a few hours of each afternoon on less than 5 successive days. The prespawning behavior was the same as the courtship display on days prior to spawning. After spawning, egg-incubating males were usually left alone. The gregarious species Apogon notatus formed territorial lasting pairs, which resided at given sites from dawn to dusk on each day during a period of a month or more. After spawning, the egg-incubating male either continued to stay with his mate in the territory, or left it to enter into an aggregation. In the latter case, the female continued to reside in the territory, pairing with a new male whom she brought from an aggregation. It is suggested that in paternal apogonids the prolonged pair bond and territoriality should have developed only in gregarious species as secondary adaptation for reproductive success: to avoid conspecific interference during spawning.     

Does Tn10 transpose via the cointegrate molecule?

Summary It has been well established that Tn3 and its relatives transpose from one replicon to another by two successive reactions: formation of the cointegrate molecule and resolution from it. Whether or not the 9300 base pair tetracycline resistance transposon Tn10 transposes in the same manner as Tn3 was investigated by two methods.In the first method, 55, a lambda phage carrying Tn10 was lysogenized in an Escherichia coli strain carrying a Tn10 insertion; the phage has a deletion in attP, hence it was lysogenized in a Tn10 sequence in the E. coli chromosome by reciprocal recombination. The chromosomal structure in these lysogens is equivalent to the Tn10-mediated cointegrate molecule of lambda and the E. coli chromosomal DNA. The stability of the cointegrate molecule was examined by measuring the rate of excision of lambda from the host chromosome, and was found to be stable, especially in a Rec^- strain. Because of this stability, the cointegrate molecule should be accumulated if Tn10 transposes via the cointegrate molecule. Then, we examined the configuration of products made by transposition of Tn10 from 55 to the E. coli chromosome. The cointegrate molecule was found in products of Tn10 transposition in a Rec⁺ strain at a frequency of 5% per Tn10 transposition, but this molecule could not be found in a Rec^- strain. Since transposition of Tn10 was recA-independent, absence of the cointegrate molecule formed in a RecA^- strain strongly suggested that the cointegrate molecule is not an obligatory intermediate of transposition of Tn10.In the second method, mobilization of pACYC177 by R388 and by R388:: Tn10 was examined. The pACYC177 plasmid was mobilized by R388::Tn10 at a frequency of 10^-4 per donor but not by R388. It occurred, in most cases, by inverse transposition of R388::Tn10 to pACYC177 forming plasmids such as pACYC177::IS10-R388-IS10. Mobilization of pACYC177 by a Tn10-mediated cointegrate in the form of pACYC177::Tn10-R388-Tn10 was not observed in crosses using a Rec^- donor. These observations also suggested that transposition of Tn10 in Rec^- cells does not occur via the cointegrate molecule.     

Life-cycle variation inPanonychus akitanus Ehara (Acarina:Tetranychidae)

The life history ofPanonychus akitanus Ehara was studied in two Hokkaido populations on dwarf bamboos. The Sapporo population overwintered both as egg and female adult onSasa senanensis, and the Tomakomai population overwintered as egg onSasa apoiensis. Mites of the Sapporo population produced four or five generations from late April to late November or early December. The eggs that had overwintered began to hatch in mid-May, and this hatching period overlapped with that of eggs laid in late April by females that had overwintered. Therefore, mites with different overwintering stages would interbreed. Most eggs that had overwintered in the Tomakomai population hatched in mid-May, and about four generations were produced before early December, when only eggs were found. The density of mites per leaf of the Sapporo population reached a maximum in early May on old leaves and in late June on new leaves, and thereafter gradually decreased. The Tomakomai population initially decreased in density after hatching in the spring, but rapidly dispersed to new leaves, reached a peak in early September, and then gradually decreased. The maximal density was about 10 times higher and the distribution was less clumped (lower values of the aggregation index,m/m) than that of the Sapporo population. This was probably because the Sapporo mites could utilize only the underside of sporadically distributed leaves which were curled by spiders, whereas the Tomakomai mites inhabited any part of the leaf undersurface of the hairy host plant. Predators observed were phytoseiid mites and larvae of gall midges. The predatory effect on the Sapporo population was not clear. In the Tomakomai population, the number of gall midges correlated with the number of spider mites better than that of phytoseiid mites.     

Control of the activation/inactivation of pyruvate, Pi dikinase from the C4 plant maize by adenylate energy charge, pyruvate, and analogs of pyruvate

Pyruvate, Pi dikinase, which is localized in the mesophyll chloroplasts of C4 plants, requires a high adenylate energy charge for conversion of the enzyme from the inactive to the active form. The inactivation process is favored by a low energy charge, being maximal at values below 0.7. Pyruvate and analogs of pyruvate, oxamate and oxalate, strongly inhibit the inactivation process at millimolar levels. The results suggest that light activation of the enzyme in vivo may be mediated by an increased adenylate energy charge in the chloroplast. Pyruvate may allow a higher steady-state level of activation to be achieved in vivo by inhibiting inactivation.     

Influence of Oxygen and Temperature on the Dark Inactivation of Pyruvate, Orthophosphate Dikinase and NADP-Malate Dehydrogenase in Maize

The influence of oxygen and temperature on the inactivation of pyruvate, Pi dikinase and NADP-malate dehydrogenase was studied in Zea mays. O₂ was required for inactivation of both pyruvate, Pi dikinase and NADP-malate dehydrogenase in the dark in vivo. The rate of inactivation under 2% O₂ was only slightly lower than that at 21% O₂. The in vitro inactivation of pyruvate, Pi dikinase, while dependent on adenine nucleotides (ADP + ATP), did not require O₂.

The postillumination inactivation of pyruvate, Pi dikinase in leaves was strongly dependent on temperature. As temperature was decreased in the dark, there was a lag period of increasing length (e.g. at 17°C there was a lag of about 25 minutes) before inactivation proceeded. Following the lag period, the rate of inactivation decreased with decreasing temperature. The half-time for dark inactivation was about 7 minutes at 32°C and 45 minutes at 17°C. The inactivation of pyruvate, Pi dikinase in vitro following extraction from illuminated leaves was also strongly dependent on temperature, but occurred without a lag period. In contrast, NADP-malate dehydrogenase was rapidly inactivated in leaves (half-time of approximately 3 minutes) during the postillumination period without a lag, and there was little effect of temperature between 10 and 32°C. The results are discussed in relation to known differences in the mechanism of activation/inactivation of the two enzymes.