Cyanide-resistant respiration in Streptomyces citreofluorescens

The capacity of Streptomycetes to carry out cyanide-resistant respiration was investigated. With the model strain, Streptomyces citreofluorescens, it was shown that deprivation of glucose followed by transition from exponential to stationary growth was coupled with declining sensitivity of cellular respiration to cyanide ions. Cyanide-resistant oxidase is located within the cytoplasmic membrane. The occurrence of the cyanide-resistant oxidase did not correspond to qualitative changes of cytochrome spectrum. Cytochrome d is involved neither in cyanide-sensitive nor in cyanide-resistant respiratory chain.     

Effects of light on respiration and oxygen isotope fractionation in soybean cotyledons

Light effects on electron flow through the cyanide-resistant respiratory pathway, oxygen isotope fractionation and total respiration were studied in soybean (Glycine max L.) cotyledons. During the first 12 h of illumination there was an increase in both electron partitioning through the alternative pathway and oxygen isotope fractionation by the alternative oxidase. The latter probably indicates a change in the properties of the alternative oxidase. There was no engagement of the alternative oxidase in darkness and its fractionation was 27‰. In green cotyledons 60% of the respiration flux was through the alternative pathway and the alternative oxidase fractionation was 32‰. Exposing previously illuminated tissue to continuous darkness induced a decrease in the electron partitioning through the alternative pathway. However, this decrease was not directly linked with the low cellular sugar concentration resulting from the lack of light because 5 min of light every 12 h was sufficient to keep the alternative pathway engaged to the same extent as plants grown under control conditions.     

Comparison of fluence-response relationships of phototropism in light- and dark-grown buckwheat

Fluence-response relationships of phototropism in light- and dark-grown buckwheat (Fagopyrum esculentum Moench.) were compared using systematically varied fluence rates and irradiation times of unilateral monochromatic blue light. Etiolated seedlings respond to most fluence rates in a tri-phasic manner. Phase one differs from classic first positive in that reciprocity is not observed and the peak occurs at a wide variety of fluences, often orders of magnitude less than those characteristic of first positive. Light-grown plants display this pattern only when stimulated by low fluence rates. Phase three is an ascending arm directly related to irradiance time and is comparable to classic second positive. Phase two is a nearly indifferent zone separating phases one and three. At the lowest fluence rates, the maximal observed curvature is greater for dark-grown than for light-grown plants and the former curve more in response to short (2-second) exposures than do the latter. At the highest fluence rates, the maximal observed curvature is much greater for light-grown than for dark-grown seedlings, particularly at irradiation times of 2 to 3 minutes or more. Tropic curvatures correlate positively with increasing fluence rate up to some inflection range, above which the relationship becomes negative. This inflection range is approximately two orders of magnitude higher for light-grown plants.     

Growth inhibitors in roots of light- and dark-grown seedlings of Zea mays

Abscisic acid and 6-methoxy-2-benzoxazolinone have been identified as growth-inhibitory compounds in the primary roots of Zea mays.     

Cyanide-resistant respiration of Pseudomonas aeruginosa bacteria]

The transition of the bacterial culture into the stationary growth phase is accompanied by an appearance of cyanide-resistant respiration. Chloramphenicol inhibits the development of cyanide-resistant respiration. The cyanide-resistant oxidase is localized in the bacterial membrane. Its appearance is not due to the quantitative and qualitative changes of flavins, non-heme iron, ubiquinone and cytochromes of the b and c types, but is accompanied by an increase in the copper content of the membrane preparations. Neither cyanide-sensitive, nor cyanide-resistant chains of the bacterial electron transfer contain cytochromes of the a type. The cyanide-resistant oxidase accepts electrons at the ubiquinone--cytochrome b level of the main respiratory chain. The cyanide-resistant respiration is not accompanied by a formation of hydrogen peroxide. Cytochrome o performs the function of cyanide-sensitive oxidase. The nature of cyanide-resistant oxidase still remains obscure.     

Cyanide-resistant respiration in photosynthetic organs of freshwater aquatic plants

The rate and sensitivity to inhibitors (KCN and salicylhydroxamic acid[SHAM]) of respiratory oxygen uptake has been investigated in photosynthetic organs of several freshwater aquatic plant species: six angiosperms, two bryophytes, and an alga. The oxygen uptake rates on a dry weight basis of angiosperm leaves were generally higher than those of the corresponding stems. Leaves also had a higher chlorophyll content than stems. Respiration of leaves and stems of aquatic angiosperms was generally cyanide-resistant, the percentage of resistance being higher than 50% with very few exceptions. The cyanide resistance of respiration of whole shoots of two aquatic bryophytes and an alga was lower and ranged between 25 and 50%. These results suggested that the photosynthetic tissues of aquatic plants have a considerable alternative pathway capacity. The angiosperm leaves generally showed the largest alternative path capacity. In all cases, the respiration rate of the aquatic plants studied was inhibited by SHAM alone by about 13 to 31%. These results were used for calculating the actual activities of the cytochrome and alternative pathways. These activities were generally higher in the leaves of angiosperms. The basal oxygen uptake rate of Myriophyllum spicatum leaves was not stimulated by sucrose, malate or glycine in the absence of the uncoupler carbonylcyanide-m-chlorophenylhydrazone (CCCP), but was greatly increased by CCCP, either in the presence or in the absence of substrates. These results suggest that respiration was limited by the adenylate system, and not by substrate availability. The increase in the respiratory rate by CCCP was due to a large increase in the activities of both the cytochrome and alternative pathways. The respiration rate of M. spicatum leaves in the presence of substrates was little inhibited by SHAM alone, but the SHAM-resistant rate (that is, the cytochrome path) was greatly stimulated by the further addition of CCCP. Similarly, the cyanide-resistant rate of O₂ uptake was also increased by the uncoupler.     

Shoot initiation in light- and dark-grown tobacco callus: the role of ethylene

Shoot-forming tobacco ( Nicotiana tabacum L. cv. Wisconsin 38) callus produces less endogenous ethylene than non-shoot-forming tissue cultured in the light (16 h photoperiod) or the dark. In shoot-forming tissue more ethylene is produced early in culture (days 0–5) than later. Also dark-grown tissue produces much more ethylene than light-grown. On the basis of experiments in which (1) gaseous ethylene was added to or (2) CO₂ removed from the flasks, (3) Ethrel (an ethylene releasing agent) and (4) 1-aminocyclopropane 1-carboxylic acid (an ethylene precursor) were added to the medium, it was determined that this gaseous phytohormone had two contrary effects on shoot initiation (shoot primordium formation). Early in culture (days 0–5) endogenous or exogenous ethylene inhibited organogenesis, but later (days 5–10) exogenous ethylene or increased endogenous ethylene production speeded up primordium formation.     

Cyanide-resistant respiration of Physarum polycephalum in course of starvation

The inhibition of respiration of $\text{Physarum polycephalum}$ microplasmodia by KCN varies between 30% and 70% of initial rate of O₂ uptake, depending on the time of starvation. The kinetics of the development of cyanide-resistant respiration and its sensitivity toward salicylhydroxamic acid (SHAM) point out that CN-resistant respiration represents the activity of the alternative pathway of the electron transport. There is no evidence that during starvation the alternative pathway of respiration is active in the absence of cyanide.     

Biochemical characteristics of thylakoid membranes in chloroplasts of dark-grown pine cotyledons

Japanese black pine (Pinus thunbergii) cotyledons were found to synthesize chlorophylls in complete darkness during germination, although the synthesis was not as great as that in the light. The compositions of thylakoid components in plastids of cotyledons grown in the dark and light were compared using sodium dodecyl sulfate-polyacrylamide gel electrophoresis patterns of polypeptides and spectroscopic determination of membrane redox components. All thylakoid membrane proteins found in preparations from light-grown cotyledons were also present in preparations from dark-grown cotyledons. However, levels of photosystem I, photosystem II, cytochrome b_[ill]/f, and light-harvesting chlorophyll-protein complexes in dark-grown cotyledons were only one-fourth of those in light-grown cotyledons, on a fresh weight basis. These results suggest that the low abundance of thylakoid components in dark-grown cotyledons is associated with the limited supply of chlorophyll needed to assemble the two photosystem complexes and the light-harvesting chlorophyll-protein complex.     

Cyanide-resistant respiration and a branched cytochrome system in Kinetoplastidae

Two functional terminal oxidases, cytochrome aa₃ and cytochrome o, are present in the cytochrome system in cyanide-sensitive trypanosomatids. The organisms examined included Crithidia fasciculata, Leptomonas sp., Blastocrithidia culicis, Herpetomonas muscarum, Leishmania tarentolae, Trypanosoma lewisi, Trypanosoma conorhini and Trypanosoma cruzi. A CO-binding protein with the spectral properties of cytochrome o has been solubilized and partially purified from C. fasciculata. In L. tarentolae, T. conorhini and C. fasciculata, 10–20% of the respiration is cyanide-resistant but is inhibited by salicylhydroxamic acid. The various possibilities of a branched electron transport system are examined and discussed.     

Citrate metabolism in. soybean cotyledons

Citrate metabolism and the citrate cleavage enzyme were investigatedin soybean (Glycine max (L.), Merr.) cotyledons throughout developmentand during the first 5 days of germination. It was noted thatboth the lipid synthesizing and the acetyl CoA generating systemsare present when the soybean seed matures, and that the activityof these systems declines throughout development as citrateincreases. Citrate represents 1% of the cotyledon dry weightat seed maturity. During the first 24 hr of germination, therewas an activation of the citrate cleavage enzyme and a concomitantdrop of some 60% in citrate content. Accompanying the drop incitrate content is the de novo synthesis of fatty acids foruse in the production of phospholipids. All of the data areconsistent with the hypothesis that acetyl CoA for lipid synthesisis supplied by the citrate molecule via the citrate cleavageenzyme and that activity of this system is necessary both duringseed development and during germination. ¹ Research was supported by cooperative investigations of theAgricultural Research Service, United States Department of Agriculture,and Illinois Agricultural Experiment Station. ² This research represents partial fulfillment of Ph.D. degree. (Received September 20, 1976; )     

Cyanide-resistant respiration of bacteria and its relation to metabolite oversynthesis

The phenomenon of cyanide-resistant respiration was studied in bacteria as well as its relation to the oversynthesis of metabolites. Cyanide-resistant respiration was shown to be common of aerobic and facultative anaerobic bacteria. The resistance of respiration to cyanide was observed when the growth of a microbial culture was inhibited or ceased entirely, provided the culture lacked the oversynthesis of metabolites. When a culture was capable of metabolites oversynthesis under such conditions, cyanide-resistant respiration (if any) declined. Therefore, there is a competition between metabolites oversynthesis and cyanide-resistant respiration, which is typical of many microorganisms.     

Fatty-acid metabolism in senescing and regreening soybean cotyledons

Changes in fatty-acid metabolism were studied in soybean (Glycine max Merr.) cotyledons during senescence as well as in cotyledons which had been caused to regreen by removal of the epicotyl from the seedling. The activities of the enzymes acetyl-CoA synthetase (EC 6.2.1.1) and fatty-acid synthetase in plastids isolated from the cotyledons decreased during senescence but increased in response to regreening. These changes in enzyme activities followed the same pattern as changes in the quantities of chlorophyll and polyunsaturated fatty acids in this tissue. The in-vivo incorporation of [¹⁴C]acetate into total fatty acids in the senescing and regreening cotyledons did not vary markedly with age. In addition, the quantity of label in fatty acids did not decrease for as much as 60 h after the removal of the substrate. During this 60-h period however, there was substantial redistribution of the label among the individual fatty acids. While the labelling pattern of the individual fatty acids did not vary significantly with respect to age in the senescing cotyledons, there was a substantial increase in the synthesis of labelled polyunsaturated fatty acids in the regreening tissue. Thus, the incorporation of [¹⁴C]acetate into fatty acids did not reflect the changes in the quantities of the individual fatty acids in senescing tissue as well as they did in regreening tissue.     

Phytochrome-mediated control of respiratory activities of mitochondria in cotyledons of dark-grown cucumber seedlings

Mitochondria isolated from cotyledons of dark-grown cucumber ( Cucumber sativus L., cv. Shimotsuki-Aonaga) seedlings after illumination with continuous far-red light showed an increased capacity for oxidation of malate or α-ketoglutarate, as compared with those from cotyledons of non-illuminated seedlings. This increase is supposed to be caused by phytochrome action (high irradiance response). Exogenous NAD⁺ had no effect on the rate of the oxidation of α-ketoglutarate or malate by mitochondria isolated from far-red light-treated cotyledons, but it enhanced the oxidation rate of mitochondria from control cotyledons to the level of mitochondria from light-treated ones. The NAD (NAD⁺+ NADH) content was higher in mitochondria isolated from continuously far-red light-treated cotyledons than in mitochondria from controls. The NAD content was also increased by the treatment with a red light pulse and this response was reversed by a subsequent far-red light pulse. It is proposed that phytochrome controls respiratory activities of cucumber mitochondria by changing the size of the NAD pool in the mitochondria.     

Sucrose uptake by developing soybean cotyledons

Sucrose uptake by excised developing soybean cotyledons shows a biphasic dependence on sucrose concentration. At concentrations less than about 50 millimolar external sucrose, uptake can be described as a carrier-mediated process, with a K_m of 8 millimolar. At higher external sucrose concentrations, a linear dependence becomes apparent, which suggests the participation of a nonsaturable component in total uptake. Sucrose absorption is dependent on the presence of an electrochemical potential gradient for protons since agents interfering with the generation or maintenance of this gradient (NaN₃ or carbonylcyanide-m-chlorophenyl hydrazone) decrease sucrose transport to a level at or below that predicted from the operation of the noncarrier-mediated process alone. The saturable component of sucrose uptake is also sensitive to the sulfhydryl-modifying compounds N-ethylmaleimide and p-chloro-mercuribenzenesulfonate. The thiol-reducing agent diethioerythritol reverses fully the p-chloro-mercuri-benzenesulfonate inhibition, but not that of N-ethyl maleim de. Sucrose transport is sensitive to external pH, being decreased at high pH₀. Since sucrose-induced depolarization of the membrane potential and carrier-mediated sucrose influx show similar pH-dependence, inhibitor sensitivity, and values of K_m for sucrose, a sucrose/proton contransport process appears to operate in developing soybean cotyledon cells. Measurement of free space and intracellular sucrose concentrations in vivo suggests that the carrier-mediated process is fully saturated and that sucrose transport may be limiting for sucrose accumulation by the developing seed.