COMPONENTS OF THE ELECTRON-TRANSFERRING SYSTEM IN ACETOBACTER SUBOXYDANS AND RECONSTRUCTION OF THE LACTATE OXIDATION SYSTEM

1. Cytochromes a₁⁵⁹⁰, b⁵⁶⁰, c₁⁵⁵⁴ and c₁⁵⁵² were isolated andpurifiedfrom a strain of Acetobacter suboxydans. The proceduresusedwere described in detail.
2. The main cytochrome band at550-560 mµ in intact cellssplitted at liquid air temperatureinto two bands, 551 mµ(strong) and 559 mµ (weak).
3. Optical and physiological properties of the four cytochromeswere investigated. Lactic dehydrogenase activity was found tobe associated with cytochrome c₁⁵⁵⁴. The two c₁-type cytochromes,especially cytochrome c₁⁵⁵⁴, persisted in their reduced formafter the purification through many steps.
4. By some combinationsof isolated components reconstruction ofthe oxygen uptake systemcould be realized.
5. The oxygen-consuming activity of purifiedoxidase preparationswas accelerated by a-tocopherol but notby Emasoll 4130 andTween 80.
6. Some discussions were made onthe nature of terminal oxidase,the role of cytochrome c₁⁵⁵²in the electron-transport system,and persistence of reducedstate of c₁-type cytochromes.
7. A possible scheme of the electron-transferringsystem of Acetobactersuboxydans was presented.

(Received May 16, 1960; )     

CHANGE OF B-TYPE HAEM CONTENT IN RELATION TO PEROXIDASE BIOSYNTHESIS IN INJURED SWEET POTATO ROOTS

The methods of quantitative analysis of b-type haem in plantswere investigated. With an improved method developed was determinedthe haem content in the supernatant, mitochondrial, and microsomalfractions of sweet potato tissue. The activities of peroxidase,catalase, and cytochrome oxidase, as well as the contents ofb-type haem and acid-insoluble nitrogen in the cellular fractionswere determined at different incubation times after cuttingof sweet potato tissue. Peroxidase and catalase increased withtime in each celluler fraction, following a short lag phase.In the mitochondrial fraction, b-type haem, cytochrome oxidase,and acid insoluble nitrogen increased linearly with time. Inthe microsomal and supernatant fraction, b-type haem increasedwith time following a short lag phase. The increase in haemcontent of the supernatant fraction appeared to be associatedwith peroxidase formation. Time course analysis showed that ⁵⁹Fe-incorporation into b-typehaem of the supernatant fraction increased with time and thatincorporation was markedly inhibited by blasticidin S. The incorporationof ⁵⁹Fe into mitochondrial haem did not increase with time andwas not inhibited by blasticidin S. Blasticidin S inhibited⁵⁹Fe-incorporation into microsomal haem. Time course analysisof b-type haem content, ⁵⁹Fe-incorporation into b-type haem,and peroxidase activity suggest that in the injured tissue haemis synthesized from low molecular weight compounds and is incorporatedinto peroxidase as the haem moiety. ¹ This paper constitutes Part 57 of the Phytopathological Chemistryof Sweet Potato with Black Rot. ² Present address: Institute for Plant Virus Research, Chiba.     

Physiological Studies on Germination of Phaseolus mungo Seeds: II. GLUCOSE AND ORGANIC-ACID METABOLISMS IN THE EARLY PHASES OF GERMINATION

The metabolism of glucose and organic acids was studied in theearly phases of germination of Phaseolus mungo seeds. Duringthe first 5–6 h of imbibition, ethanol fermentation activelyoccurred and in the following stage the TCA cycle seemed tobe markedly activated. CO₂ fixation seemed to be low, at leastin the early stage of germination. Aspartic acid was convertedactively into malic acid. This seemed to be a cause of the activesynthesis of malic acid observed.     

Ontogeny of growth, respiration and feeding rate of the freshwater calanoid copepod Eudiaptomus graciloides

The calanoid copepod, Eudiaplomus graciloides, was reared fromegg to adult on uni-algal diets (0.1. 0.5 and 2.5 mg dry wt1^–1) using the green alga, Chlamydomonas reinhardtii,as food, or on a mixed diet consisting of Lake Esrom water filteredthrough a plankton net with pore size 45 µm and supplementedwith C. reinhardtii (2.5 mg dry wt 1^–1). On the mixeddiet at 21.0°C growth in body dry wt (W, µg dry wt)was exponential, and the growth constants were 0.21 day^–1in the early to mid juvenile stage (N1 - C4) and 0.11 day^–1in the late juvenile to early adult stage (C4-A). At 14.5°Cthe corresponding growth rate constants were 0.10 and 0.08 day^–1.Similar growth rates were found at uni-algal concentrationsof 0.5 and 2.5 mg dry wt I^–1, and it was argued that thethreshold concentration for growth in Eudiaptomus was closeto 0.1 mg dry wt I^–1. The clearance (C, ml h^–1)of copepodites was measured on the uni-algal diets. The constantsof the regression (C = aW^b) were: a = 0.125, b = 0.858 (2000C. reinhardtii ml^–1), a = 0.068, b = 0.849 (10 000), a= 0.028, b = 0.875 (50 000). Ingestion rates were calculatedfrom the clearances and the average algal concentrations. Atthe three food levels the average daily rations were 30, 67and 125% of body dry wt. The respiration rate (R, nl O₂ h^–1)was measured in individuals reared on the mixed diet. The constantsof the regression (R = aW^b) were: a = 4.82, b = 1.07 (nauplii,14.5°C), a = 4.17, b = 0.904 (copepodites and adults, 14.5°C),a = 6.87, b = 0.757 (copepodites and adults, 21.0°C). Nosignificant difference in the respiration rate of copepoditesreared on uni-algal diets and the mixed diet could be demonstrated.Energy budgets were calculated. The assimilation efficiencyand the gross growth efficiency of copepodites decreased markedlywith increasing food concentration, the net growth efficiencyvaried from an average of 0.44 at the lowest algal concentrationto 0.60 on the mixed diet. The results are discussed in relationto previous findings with both freshwater and marine copepods.     

The Effect of Salinity Stress upon Protein Synthesis of Germinating Wheat Embryos

Two differently salt-sensitive wheat genotypes were imbibedin 0·4 M NaCl for 72 h or, alternatively, for 48 h andthen transferred to water. Seed germination, fresh weight andprotein synthesis in embryos were determined. The followingdifferences were found in the synthesis of in vivo [³⁵S]methionine-labelledproteins during salt imbibition: (a) a general decrease or disappearanceof polypeptides specific to the radicle emergence phase in thesalt-sensitive genotype; (b) a new synthesis of polypeptideswhich are not found during water imbibition and are common toboth genotypes; (c) a differential synthesis of polypeptidesthat are unique to each cultivar. Upon return to water, salt-inducedproteins ceased to be synthesized while proteins associatedwith an advanced germination phase were actively produced. Theseresults suggest that the expression of 'salt stress' proteinsis related to the adaptation process of seeds to salinity aswell as to the genetic constitution of a selected salt-tolerantgenotype.Copyright 1993, 1999 Academic Press Triticum durum, wheat, embryo, salt stress, protein synthesis     

Studies on the Initial Biochemical Reactions in the Germination of Pollen Grains

Tritiated water (³HHO) has been used as the medium for the germinationof pollen grains of Pinus radiata D.Don (a gymnosperm), Ulexeuropaeus L., Salix caprea L. (dicotyledonous angiosperms),and Phormium tenax Forst. (a monocotyledonous angiosperm). ³H-labelledcompounds formed during the initial germination (egersis) periodhave been separated and identified to give information on themetabolism taking place.Since the earliest labelled compoundswere -aminobutyric acid, alanine, aspartic acid, and glutamicacid, it is concluded that these amino acids play an importantpart in the biochemical reactions during the early stages ofgermination. Citric acid, malic acid, and glutamine do not becomelabelled until later while carbohydrates, phosphate esters,and lipids do not appear to incorporate tritium within the firsthour of germination.The gross labelling pattern and the natureof the individually labelled metabolites, their intensity andsequence of labelling are similar for all the species investigatedexcept gorse, which showed a decrease in the intensity and thenumber of labelled metabolites with time.P. radiata pollen storedfor 3 years under vacuum or carbon dioxide has a labelling patternsimilar to freshly collected P. radiata pollen, except for aconsiderable increase in the amount of an unknown metabolite(Compound X).     

Changes in cytochrome contents and respiratory activity of Bacillus cereus Strain T during germination, vegetative growth and sporulation

Vegetative cells of Bacillus cereus Strain T contain cytochromeb-562, a minor b-type component, in addition to known components,cytochrome a+a₃, cytochrome b-557 and cytochrome c-551. Also,the spores contain low but definite amounts of cytochromes b-562and c-551, which were oxidized when the spores were shaken withair. Contents of cytochromes a, b and c per cell and per cellnitrogen, and the activity of glucose oxidation increased duringspore germination and elongation. During the stage precedingfirst cell division, cytochrome contents per cell increasedin parallel with the increase of cell nitrogen, while the activityof glucose oxidation decreased. During early exponential growth,the content of cytochrome b per cell nitrogen and respiratoryactivity with glucose again increased. When cells entered thesporulation stage, characterized by structural changes insidethe cells, the activity of glucose oxidation began to decrease,while that of acetate or succinate oxidation started to increase.During the sporulation process, the contents of the three cytochromecomponents continued to increase and reached the highest levelin cells containing completed spores, but the activity of respirationwith endogenous or added substrates was negligible in thesecells. (Received November 10, 1975; )     

Cloning and characterization of a sialidase from the murine histocompatibility-2 complex: low levels of mRNA and a single amino acid mutation are responsible for reduced sialidase activity in mice carrying the Neula allele

The Neu1 locus, in the S region of the murine histocompatibility-2complex, regulates the sialic acid content of several liverlysosomal enzymes. Three alleles, Neu1^a, Neu1^b, and Neu1^c, havebeen described on the basis of differential sialylation of theenzyme liver acid phosphatase. The Neu1^a allele occurs in asmall number of mouse strains, e.g., SM/J and is associatedwith sialidase deficiency. We recently described G9, a sialidasegene in the human major histocompatibility complex (Milner etal. (1997) J. Biol. Chem., 272, 4549–4558), and we nowreport the characterization of the equivalent gene in mouse.The protein product of the murine G9 gene is 409 amino acidsin length and is 83% identical to its human orthologue. Expressionof the murine G9 protein in insect cells has confirmed thatit is a sialidase, with optimal activity at pH 5. To elucidatethe basis of sialidase deficiency in mouse strains carryingthe Neu1^a allele, we have sequenced the G9 coding regions frommice carrying the three Neu1 alleles and hence defined the aminoacid sequence characteristic of each allotype. Of particularinterest is a Leu-209 to Ile mutation that is unique to theNeu1^a allotype and is associated with reductions in sialidaseactivity of 68% and 88% compared to the Neu1^b and Neu1^c allotypes,respectively, when these three protein variants are expressedin insect cells. Additional factors, such as differential expression,may also influence the activities of the Nen1 allotypes in vivo.We have observed that the level of G9 mRNA is substantiallyreduced in mice carrying the Neu1^a allele compared to the Neu1^b(85–95% reduction) and Neu1^c (70% reduction) alleles. H2 complex MHC Neu1 sialidase     

CHLOROPHYLL FORMATION IN ISOLATED PUMPKIN COTYLEDONS IN THE PRESENCE OF KINETIN AND CHLORAMPHENICOL

Investigations have been made on the changes in the levels ofprotochlorophyll, chlorophyll a and chlorophyll b in relationto the kinetin induced expansion of isolated pumpkin cotyledonsin the presence and absence of chloramphenicol. It has been shown that rise in pigment level keeps pace withexpansion growth of the cotyledons. Kinetin markedly promotes the synthesis of protochlorphyll withoutmuch affecting the rate of its photoreduction to chlorophyll. Chloramphenicol strongly inhibits the development of both chlorophylla and b. The inhibition seems to be due to its interferenceboth with the synthesis of protochlorophyll and its subsequentconversion to chlorophyll. The inhibitory effect of chloramphenicol on the formation ofchlorophyll a is greater than on that of chlorophyll b, suggestingthereby the probability of divergent pathways for the formationof the two chlorophylls. (Received December 21, 1966; )     

Effects of growth conditions on formation of cytochrome system of a denitrifying bacterium, Pseudomonas stutzeri

Cytochrome systems in cells of a denitrifying bacterium, Pseudomonasstutzeri (VAN NIEL strain), grown under different atmosphericconditions were compared with reference to the effects of nitrateand nitrite on cytochrome synthesis. When a culture was sufficiently aerated (aerobic conditions),synthesis of all cytochrome components was repressed, regardlessof the presence or absence of nitrate and nitrite. When aeratedmoderately (semi-aerobic conditions), both soluble and paniculatecytochromes c-552 and cytochrome b-558 contents markedly increasedeven in the absence of nitrate and nitrite. Under anaerobic or semi-aerobic conditions, nitrite inducedcytochrome a₂–c synthesis. This inductive effect of nitritewas counteracted by nitrate. Nitrate also repressed particulatecytochrome c-552 synthesis to some extent but nitrite did not. ¹Present address: Department of Biochemistry, Hiroshima UniversitySchool of Dentistry, Hiroshima, Japan (Received June 24, 1969; )     

Growth of grana from "primary" thylakoids in Phaseolus vulgaris

The plastids of young dark-grown bean leaves, exposed to periodiclight are agranal, devoid of chlorophyll b and contain primarythylakoids and chlorophyll a. Transfer of these plants to continuousillumination results in synthesis of new chlorophyll a, chlorophyllb and grana. This study was done in order to study whether andhow the grana are formed from preexisting primary thylakoids.¹⁴C--aminolevulinic acid was used to label the chlorophyll aof the primary thylakoids, and its fate was studied after transferof the plants to continuous light. It was found that chlorophyll b and grana become ¹⁴C-labelled.The total radioactivity of chlorophyll b per bean increasedwith the parallel decrease of that of chlorophyll a. All subchloroplastfractions, obtained after digitonin disruption of chloroplasts,contained chlorophyll a of equal specific radioactivity. Thespecific radioactivity of chlorophyll b was lower than thatof chlorophyll a, and, in addition, it was lower in the granathan in the stroma lamellae fraction. The data suggest that chlorophyll b is formed from chlorophylla; the grana are formed by stacking of preexisting primary thylakoids;chlorophyll b is synthesized faster in the grana than the stromalamellae; the newly formed chlorophyll a molecules are distributedat random throughout the developing photosynthetic membraneand not on specific growing sites. (Received April 24, 1976; )     

Export, Mobilization, and Respiration of Assimilates in Uniculm Barley during Light and Darkness

The respiratory losses and the pattern of carbon supply froma leaf of unicuim barley were examined during a complete diurnalperiod using a steady state ¹⁴C-labelling technique. After a delay of c. 1 h a portion of the ¹⁴C exported from acontinuously assimilating leaf was lost in respiration in thelight. This respiratory loss amounted to c. 20% of the total¹⁴C fixed. A further 28% of the total ¹⁴C fixed was respiredduring the dark period. In the light, carbon was fixed at a rate of c. 8·9 mgC dm^{–2 h–1} and exported from the leaf at ^c. 5·3mg C dm^{–2 h–1}. Dark export averaged ^c. 31% of theday-time rate. Carbohydrate was stored in the leaf during the day and was almostcompletely remobilized during the dark. Sucrose, the major reservecarbohydrate, was exported first whilst the starch level remainedconstant. After some 9 h of darkness, sucrose declined to alow level and starch remobilization began.     

Studies on Foliar Penetration: I. FACTORS CONTROLLING THE ENTRY OF 2, 4 - DICHLOROPHENOXYACETIC ACID

A technique, using leaf disks, has been developed to study thepenetration of isotopically labelled compounds into leaves underconditions where there is no appreciable change in the concentrationof the external solution and no subsequent translocation. Inthis preliminary survey, the leaves of Phaseolus vulgaris andColeus Blumei were employed to investigate the entry of 2,4-dichlorophenoxyaceticacid (2,4-D), labelled in the carboxyl group with ¹⁴C. Over3 days there is no loss of ¹⁴C to the atmosphere from treatedleaves of Phaseolus. The rate of penetration is enhanced when(a) the leaves are young, (b) the water status is lowered, (c)the temperature is raised (Q₁₀=2.3–2.8), and (d) a surface-activeagent is added to the external solution. Penetration is alsofavoured by a decrease in the pH, the relation indicating thatboth ions and molecules enter. Penetration is greater in thelight and prior illumination of the tissues positively affectsthe subsequent rate in the light, but not in the dark. In boththe light and the dark considerably more 2,4-D penetrates theabaxial surface of Phaseolus leaves. For Coleus an even greaterdifference between surfaces is found in the light but not inthe dark. For both species in the light the rates of entry intoboth surfaces are proportional to their respective stomataldensities. The simultaneous addition of indoleacetic acid tothe external solution caused more 2,4-D to enter Phaseolus leaves,but the addition of triiodobenzoic acid restricts entry. Therate of penetration remains constant over 24 hours and between0.1 and 200 mg./l. the rate is linearly related to concentration.Subsequent to entry, the 2,4-D is in a form which does not diffusefrom the tissue into buffer or exchange with unlabelled 2,4-D.Moreover, no outward movement takes place from treated tissuewhich has been frozen and thawed. These findings are discussedin relation to previous work on foliar penetration. It is concludedthat at least with Phaseolus penetration largely takes placethrough the guard cells and/or accessory cells.     

Studies on the metabolism of a sulfur-oxidizing bacterium VII. Oxidation of sulfite by a cell-free extract of Thiobacillus thiooxidans

Properties of the cell-free extract, prepared from a strainof Thiobacillus thiooxidans by sonic disruption followed byfractionation with centrifugatiori, were investigated with referenceto its sulfite-oxidizing activity. Without the addition of cofactors the particulate fraction(F-P)catalyzed oxidation of sulfite with oxygen or bacterial cytochromec-552 obtained from Pseudomonas stutzeri as electron acceptor.TMPD reduced by ascorbic acid was also oxidized by F-P. Thesoluble fraction(F-S) showed no activity in oxidizing sulfiteand TMPD, but stimulated TMPD oxidation by F-P. Oxygen uptake with either sulfite or TMPD as substrate was inhibitedby KCN, NaN₃, CO and c-phenanthroline. CO-Inhibition was reversedby light. Reduction of cytochrome c-552 by sulfite was insensitiveto these agents. Antimycin A markedly inhibited sulfite oxidation with eitheroxygen or cytochrome c-552 as electron acceptor, but was withouteffect on TMPD oxidation. DDC and SAO, both strong inhibitors of sulfur oxidation, didnot affect sulfite and TMPD oxidations. Cytochromes of the a, b and c types were contained in F-P. Thesecytochromes were rapidly reduced when F-P was incubated withsulfite. Cytochrome(s) of the c type was present in F-S, too. ¹VI.=References (3) ²Partly supported by a grant from the Ministry of Education ³Present address: Sanyo Women's College, Hatsukaichi, Hiroshima738, Japan ⁴Present address: Department of Biochemistry, Hiroshima UniversitySchool of Dentistry, Hiroshima 734, Japan (Received May 15, 1970; )     

Yield-density Relationships: the Influence of Resource Availability on Growth and Self-thinning in Populations of Vulpia fasciculata

Monocultures of Vulpia fasciculata were grown over a wide rangeof densities to investigate the influence of crowding and nutrientsupply on growth and self-thinning. For a given time and densityseries the relationship between mean yield per plant (w) andthe density of survivors (N) could be described by the equation w= w_m (1+aN)^–b. where w_m is the yield of an isolated plant, a is the area requiredto achieve a yield of w_m and b describes the effectiveness withwhich resources are taken up from the area. All three parametersincreased with time. Adding nutrients changed not only the rate at which the effectsof crowding occurred but also the intensity of crowding since w_m = C(a^b)^D. where C and D are constants. The addition of nutrients resultedin an increase in the value of C. Such an increase means thata larger weight can be supported by a given area because theresources within that area are greater. During the early phases of growth, populations of V. fasciculataconformed to the –3/2 power law, w = cN^–3/2, butonly at very high densities with a plentiful supply of nutrients.However, once the maximum standing crop had been reached thetrajectory of the thinning line switched to a slope of justless than –1 when weight was ploted against density onlogarithmic scales. The intercept of the –3/2 thinningline was considerably higher (log c = 5.74) than those for mosttrees and forbs but was similar to those of a number of othergrasses. Vulpia fasciculata, dune fescue, yield-density models, self-thinning, density-dependence, nutrient supply     

ELECTRON TRANSPORT SYSTEMS OF RHIZOBIUM GROWN IN NODULES AND IN LABORATORY MEDIUM

The electon transport systems of Rhizobium japonicum were studied,comparing cells harvested from effective nodules with thosefrom artificial culture. Participation of the cytochrome systemwas confirmed in both forms of cells. Absorption peaks of thecytochromes of cultured cells were a, b, c type, resemblingthose of Bacillus subtilis, yeast and mammalian tissue. Cytochromea could not be detected in the absorption spectrum of symbioticcells, although the CO binding difference spectrum showed apeak at about 438 mµ, which can be attributed to a componenta₃ or a₁. CO difference spectrum also showed a shoulder at about416 mµ. Cells cultivated under the insufficient supply of oxygen showedthe cytochrome absorption spectrum closely resembled that ofsymbiotic cells. Diaphorase activity was lower in symbioticcells. These results are considered to be due to the insufficientsupply of oxygen within nodule tissue. Succinate oxidation bythe symbiotic cell paniculate was shown to be carbon monooxideresistant. NADH₂ oxidation by the supernatant fraction of symbioticcells was accelerated by flavin mononucleotide, 2, 6-dichiorophenolindophenol, methylene blue and vitamin K₃. ¹Present address: Faculty of Agriculture, Tôhoku University,Sendai. ²Present address: Central Agricultural Experiment Station, Kitamoto.     

Light Actions in the Germination of Cocklebur Seeds: IV. DISAPPEARANCE OF RED LIGHT-REQUIREMENT FOR THE GERMINATION OF UPPER SEEDS SUBJECT TO ANOXIA, CHILLING, CYANIDE OR AZIDEPRETREATMENT

Esashi, Y., Fuwa, Nn Kojima, K. and Hase, S. 1986. Light actionsin the germination of cocklebur seeds. IV. Disappearance ofred light-requirement for the germination of upper seeds subjectto anoxia, chilling, cyanide or azide pretreatmenL—J.exp. Bot. 37: 1652–1662. The effects on the germination of positively photoblastic uppercocklebur (X anthium pennsylvanicum Wallr.) seeds by pretreatingwith anoxia, chilling, cyanide or azide, which stimulates theirdark germination, were examined in relation to light actions.Prior to experiments, seeds were pre-soaked at 23 °C inthe dark for 1 or 2 weeks to remove the pre-existing Pfr. Whenthe prctreatment conditions were suboptimal for germinationinduction, the stimulating effects of the pretreatments on germinationduring a subsequent dark period at 23 °C were manifest onlywhen seeds were irradiated with red light before or after thepretreatment Red light promotion was reversed by blue or far-redlight treatment. However, both prc-chilling for 6 d at 8 °Cand prctreatment with 1· 5 mol m ^{– 3} NaN³ for 2d could induce full germination without red light exposure.On the other hand, both pre-exposure to anoxia for 8 d and pretreatmentwith 30 mol m^–3 KCN could induce the dark germinationonly when germination occurred at 33 °C which is known toaugment the ratio of an alternative respiration flux to a cytochromeone. Moreover, the dark germination in response to these inductionswere strongly inhibited by the inhibitors of alternative respiration,propyl gallate and benzohydroxamic acid, applied during a subsequentdark period. It was thus suggested that Pfr has some relationto the operation of two respiration systems of cocklebur seeds,but it is not indispensable to germination of this positivelyphotoblastic seed. Key words: Anoxia, azide, blue light, chilling cyanide, dark germination, far-red light, red light, seed germination, X anthium pennsylvanicum     

Effects of 5-Aminolevulinic Acid on the Accumulation of Chlorophyll b and Apoproteins of the Light-Harvesting Chlorophyll a/b-Protein Complex of Photosystem II

The effects were examined of 5-aminolevulinic acid (ALA) onthe accumulation of Chl and apoproteins of light-harvestingChl a/b-protein complex of photosystem II (LHCII) in cucumbercotyledons under intermittent light. A supply of ALA preferentiallyincreased the accumulation of Chl a during intermittent illumination.However, when cotyledons were pretreated with a brief exposureto light or benzyladenine (BA), the stimulatory effect of ALAon the increase in the level of Chl b was greater than thatin the level of Chl a, resulting in decreased ratios of Chla/b. Time-course experiments with preilluminated cotyledonsrevealed that LHCII apoproteins accumulated rapidly within thefirst 30 min of intermittent illumination with a decline duringsubsequent incubation in darkness. A supply of ALA did not affectthe accumulation of LHCII apoproteins during the intermittentlight period, but it efficiently inhibited the decline in theirlevels during the subsequent darkness. After exposure to a singlepulse of light of BA-treated cotyledons, the prompt increasein levels of LHCII apoproteins was not accompanied by the formationof Ch b, which began to accumulate later. The pattern of changesin levels of LHCII apoproteins was quite similar to that inlevels of Chl a. These results suggest that LHCII apoproteinsare first stabilized by binding with Chl a and that an increasedsupply of Chl a and the accumulation of LHCII apoproteins areprerequisites for the formation of Chl b. ¹Present address: Department of Chemistry, Faculty of Scienceand Technology, Meijo University, Aichi, 468 Japan.     

ON THE NATURE OF MOSS OXALIC ACID OXIDASE

Moss oxalic acid oxidase freed from catalase by boiling is stronglyinhibited by the "metal-complexing" compounds such as thiocyanate,azide, diethyldithiocarbamate, and hydrosulfite. Inactivatedby dialysis against thiocyanate or azide, the enzyme can bereactivated to a considerable extent by the addition of ferricsalt, cytochrome-c or hemoglobin, not by other metal ions, suchas Cu²⁺, Zn²⁺ , Mn²⁺, and Fe²⁺. Nitrate, chlorate, monoiodoacetate,and iodide also act as strong inhibitors towards moss oxalicacid oxidase. Some enzyme fractions which were obtained by the sodium sulfateprecipitation method were stimulated by Fe³⁺, but not by cytochrome-cor by other metallic ions. This stimulation was inhibited bythiocyanate, azide and monoiodoacetate. ¹ Present address: Biological Institute, University of Toyama,Toyama     

Changes in the Levels of Chlorophyll and Light-Harvesting Chlorophyll a/b Protein of PS II in Rice Leaves Aged under Different Irradiances from Full Expansion through Senescence

Effects of irradiance on changes in the amounts of chlorophyll(Chl) and light-harvesting chlorophyll a/b protein of PS II(LHCII) were examined in senescing leaves of rice (Oryza sativaL.). Results of treatments at two irradiances (100% and 20%natural sunlight) were examined after the full expansion ofthe 13th leaf throughout the course of senescence. With 20%sunlight, the Chl content decreased only a little during leafsenescence, while with 100% sunlight it decreased appreciably.Similarly, the amount of LHCII protein during treatment with20% sunlight remained almost constant. However, the ratio ofChl a/b during the shade treatment decreased significantly andthe rate of decrease was greater than during the full-sunlighttreatment. The ratio of Chl a/b for Chl a and b bound to LHCIIwas about 1.2, irrespective of leaf age or irradiance treatment.When the amounts of Chl bound to LHCII were calculated fromthe total leaf content of Chl and the ratio of Chl a/b, assuminga ratio of Chl a/b bound to LHCII of 1.2, they were well correlatedwith the amounts of LHCII protein. Changes in the amounts of LHCII synthesized during the two irradiancetreatments were examined using an ¹⁵ tracer. Incorporation of¹⁵N into LHCII declined dramatically during both treatmentsfrom full expansion through senescence, suggesting that therewas little synthesis of LHCII protein during that time. In addition,the amount of LHCII synthesized during senescence was lowerduring the shade treatment than during the 100% sunlight treatment.These results indicate that the absence of an apparent changein levels of LHCII with shade treatment during senescence wascaused by the very low rate of turnover of LHCII protein. (Received June 17, 1992; Accepted September 28, 1992)