Heterogeneity in chloroplast photosystem II

Photosystem-two (PSII) in the chloroplasts of higher plants and green algae is not homogeneous. A review of PSII heterogeneity is presented and a model is proposed which is consistent with much of the data presented in the literature. It is proposed that the non-quinone electron acceptor of PSII is preferentially associated with the sub-population of PSII known as PSIIß.Abbreviations and symbols ATP Adenosine triphosphate - Chl Chlorophyll - C₅₅₀ Absorbance bandshift at 550 nm; proportional to [Q_A ^-] - D, D Components involved ir electron donation to P680 - pH Transthylakoid proton gradient - Transthylakoid electrical gradient - DCMU 3-(3,4-Dichlorophenyl)-1,1-dimethylurea referred to as diuron - E _h Oxidation-reduction potential - E _m Cxidation-reduction midpoint potential - EPR Electron paramagnetic resonance - Fm Fluorescence yield when all traps are closed - Fo Fluorescence yield when all traps are open - Fv Variable fluorescence equal to Fm-Fo - Fi Initial fluorescence yield, (usually equivalent to Fo in dark-adapted thylakoids) - Hepes 2-hydroxyethylpiperazine-N-2-ethane sulphonic acid - LHCP Light-harvesting chlorophyll a/b binding protein - PQ Plastoquinone - PSII Photosystem II - P680 Reaction centre chlorophyll of PSII - P₅₁₈ Absorbance bandshift at 518 nm, reflects asymmetric charge distribution across the thylakoid membrane - Q_A, _QH , Q₁ Primary stable plastoquinone electron acceptor of PSII; a quencher of fluorescence - Q _B , B, R Plastoquinone associated with the Q _B -protein, the two-electron gate - Q _D , Q₂, X _a Non-quinone electron acceptor of PSII - X₃₂₀ Absorbance bandshift at 320 nm; semiquinone anion indicator     

The action of lipase on chloroplast membranes: II. Polypeptide patterns of bean galactolipase- and phospholipase A2-treated thylakoid membranes

Thylakoid membranes obtained from bean chloroplasts treated with bean galactolipase or phospholipase A₂ (from Crotalus terr. terr.) showed marked changes in their polypeptide patterns when separated on SDS-PAGE. The obtained results have been discussed with regard to the relationship between chloroplast lipids and polypeptides originating from chlorophyll-protein complexes of bean thylakoids. A coexistence between galactolipids and the peripheral antennae in PS I complex and LHCP³ as well as a conspicuous role of phospholipids in PSI and PSII centre chlorophyll-protein complexes has to be underlined.Abbreviations CP1 chlorophyll a-protein complex of PSI - CPa chlorophyll a-protein complex of PSII - D₁₀ digitonin subchloroplast particles enriched in PSII - D₁₄₄ digitonin subchloroplast particles enriched in PSI - DCMU 3-(3,4-dichlorophenyl)-1,1-dimethylurea - LHCP^1–3 light harvesting chlorophyll a/b protein complexes - PAGE polyacrylamide gel electrophoresis - PSI photosystem I - PSII photosystem II - SDS sodium dodecyl sulphate - TCA trichloroacetic acid - Tricine N-Tris-(hydroxymethyl)-methylglycine - Tris Tris-(hydroxymethyl)-aminomethan     

Spatio-temporal patterns of photosystem II activity and plasma-membrane proton flows in Chara corallina cells exposed to overall and local illumination

Pulse-amplitude modulated microfluorometry and an extracellular pH microprobe were used to examine light-induced spatial heterogeneity of photosynthetic and H⁺-transporting activities in cells of Chara corallina Klein ex Willd. Subcellular domains featuring different PSII photochemical activities were found to conform to alternate alkaline and acid zones produced near the cell surface, with peaks of PSII activity correlating with the position of acid zones. Buffers eliminated pH variations near the cell surface but did not destroy the variations in PSII photochemical yield (F/F_m). When a dark-adapted cell was exposed to actinic light, the PSII effective yield decreased within 5–15 min in the alkaline regions but rose after the initial decline in the acid regions. The light-induced decrease in F/F_m in the alkaline regions occurred prior to or synchronously with the steep rise in local pH. The kinetics of F/F_m, F_m, and F observed in alkaline regions under overall illumination of Chara cells were replaced by those typical of acid regions, when the illumination area size was restricted to 1.5–2 mm. The data show that photoinduced patterns in photosynthetic activity are not predetermined by the particular structural organization of alkaline and acid cell regions but are subject to dynamic changes.Abbreviations APW artificial pond water - a.u. arbitrary units - F_o and F_m minimal and maximal chlorophyll fluorescence yields in a dark-adapted cell - F and F_m actual (running) and maximal fluorescence yields in a cell exposed to actinic light - F/F_m(F_m–F)/F_m effective quantum yield of PSII photochemistry - pH_o pH of the medium near the cell surface - PSII photosystem II     

Localization of adenosine 5′-phosphosulfate sulfotransferase in spinach leaves

Roots of spinach (Spinacia oleracea L.) seedlings contained only a very low activity of adenosine 5-phosphosulfate sulfotransferase compared to the cotyledons. Adenosine 5-phosphosulfate sulfotransferase activity increased about tenfold in cotyledons during greening. Preparation of organelle fractions from spinach leaves by a combination of differential and isopycnic density gradient centrifugation showed that adenosine 5-phosphosulfate sulfotransferase banded with NADP-glyceraldehyde-3-phosphate dehydrogenase, a marker enzyme for intact chloroplasts. In the fractions of peroxisomes, mitochondria and broken chloroplasts virtually no adenosine 5-phosphosulfate sulfotransferase activity was measured. Comparison with the chloroplast enzyme NADP-glyceraldehyde-3-phosphate dehydrogenase indicates that in spinach, adenosine 5-phosphosulfate sulfotransferase is localized almost exclusively in the chloroplasts.Abbreviations APS Adenosine 5-phosphosulfate - APSSTase Adenosine 5-phosphosulfate sulfotransferase - BSA Bovine serum albumin - BRIJ58 Polyethylene glycolmonostearylether - DTE Dithioerythritol - DTT Dithiothreitol - EDTA Ethylenediaminetetraacetic acid - ME 2-Mercaptoethanol - NADP-GPD NADP-linked glyceraldehyde-3-phosphate dehydrogenase - PAPS Adenosine 3-phosphate 5-phosphate 5-phosphosulfate - POPOP 1,4 Di [2-(5-phenyloxazolyl)]-benzene - PPO 2,5-Diphenyloxazol The results presented in this paper are taken from the Ph. D. thesis of H.F.     

Spontaneous chlorophyll mutants of Pennisetum americanum: Genetics and chlorophyll quantities

Summary Thirteen spontaneously occurring chlorophyll deficient phenotypes have been described and their genetic basis was established. Ten of these — white, white tipped green, patchy white, white virescent, white striping 1, white striping 2, white striping 4, fine striping, chlorina and yellow virescent showed monogenic recessive inheritance and the remaining three — yellow striping, yellow green and light green seedling phenotypes showed digenic recessive inheritance. The genes for (i) white tipped green (wr) and yellow virescent (yv) and (ii) patchy white (pw) and white striping 1 (wst 1) showed independent assortment. Further, the genes for white (w), white tipped green (wr) and yellow virescent (yv) were inherited independently of the gene for hairy leaf margin (Hm).In the mutants — white tipped green, patchy white, white striping 1, white striping 2, fine striping, chlorina, yellow virescent, yellow striping, yellow green and light green phenotypes total quantity of chlorophyll was significantly less than that in the corresponding controls, while in white virescent there was no reduction in the mature stage. For nine of the mutants the quantity of chlorophyll was also estimated in F₁'s (mutant x control green). In F₁'s of six of the mutants — white tip, patchy white, chlorina, yellow virescent, fine striping and yellow striping the quantity of chlorophyll was almost equal to the wild type. In the F₁'s of three of the mutants — white striping 1, white striping 2 and light green an intermediate value between the mutant and wild types was observed. In yellow virescent retarded synthesis of chlorophyll, particularly chlorophyll a was observed in the juvenile stage. Reduced quantity of chlorophyll was associated with defective chloroplasts. In the mutants — white tipped green, white virescent, fine striping, chlorina, yellow striping, yellow green and light green defective plastids were also observed. In patchy white secondary destruction of chlorophylls and the presence of defective plastids were found to be associated with reduced chlorophyll quantity at maturity.Paper chromatographic studies of leaf flavonoids revealed some variation between the inbreds, but there were three common spots, 7, 8 and 9, except for PDP in which the spot 8 was absent. Chlorophyll deficient mutants differed from their respective controls in the absence of one or more of the spots present in the controls and in the presence of new spots in some of the mutants.Most of the chlorophyll mutants showed higher survival rate in the Kharif season than in Rabi season which was attributed to the higher mean day temperature and longer day light period in the Kharif season than in Rabi season.     

Temperature-sensitive coupling and uncoupling of ATPase-mediated,nonradiative energy dissipation: Similarities between chloroplasts and leaves

The effects of temperature on the dark relaxation kinetics of nonradiative energy dissipation in photosystem II were compared in lettuce (Lactuca sativa L.) chloroplasts and leaves of Aegialitis annulata R. Br. After high levels of violaxanthin de-epoxidation in the light, Aegialitis leaves showed a marked delay in the dark relaxation of nonradiative dissipation, measured as non-photochemical quenching (NPQ) of photosystem II chlorophyll a fluorescence. Aegialitis leaves also maintained a moderately high adenylate energy charge at low temperatures during and after high-light exposure, presumably because of their limited carbon-fixation capacity. Similarly, dark-sustained NPQ could be induced in lettuce chloroplasts after de-epoxidizing violaxanthin and light-activating the ATP synthase. The duration and extent of dark-sustained NPQ were strongly enhanced by low temperatures in both chloroplasts and leaves. Further, the NPQ sustained at low temperatures was rapidly reversed upon warming. In lettuce chloroplasts, low temperatures sharply decreased the ATP-hydrolysis rate while increasing the duration and extent of the resultant trans-thylakoid proton gradient that elicits the NPQ. This was consistent with a higher degree of energy-coupling, presumably due to reduced proton diffusion through the thylakoid membrane at the lower temperatures. The chloroplast adenylate pool was in equilibrium with the adenylate kinase and therefore both ATP and ADP contributed to reverse coupling. The low-temperature-enhanced NPQ quenched the yields of the dark level (F_o) and the maximal (F_m) fluorescence proportionally in both chloroplasts and leaves. The extent of NPQ in the dark was inversely related to the efficiency of photosystem II, and very similar linear relationships were obtained over a wide temperature range in both chloroplasts and leaves. Likewise, the dark-sustained absorbance changes, caused by violaxanthin de-epoxidation (A_508nm) and energy-dependent light scattering (A_536nm) were strikingly similar in chloroplasts and leaves. Therefore, we conclude that the dark-sustained, low-temperature-stimulated NPQ in chloroplasts and leaves is apparently directly dependent on lumen acidification and chloroplastic ATP hydrolysis. In leaves, the ATP required for sustained NPQ is evidently provided by oxidative phosphorylation in the mitochondria. The functional significance of this quenching process and implications for measurements of photo-protection versus photodamage in leaves are discussed.Abbreviations and Symbols A antheraxanthin - Chl chlorophyll - DPS de-epoxidation state of the xanthophyll cycle, ([Z+A]/[V+A+Z]) - F, F steady-state fluorescence in the absence, presence of thylakoid energization - F_o, F_o dark fluorescence level in the absence, presence of thylakoid energization - F_m, F_m maximal fluorescence in absence, presence of thylakoid energization - NPQ nonphotochemical quenching (F_m/F_m)–1 - V violaxanthin - Z zeaxanthin - NRD nonradiative dissipation - PFD photon flux density - [2ATP+ADP] - pH trans-thylakoid proton gradient - S pH-dependent light scattering - _PSII (F_m–F)/F_m, photon yield of PSII photochemistry at the actual reduction state in the light or dark - [ATP+ADP+AMP] We thank Connie Shih for skillful assistance in growing plants and for conducting HPLC analyses. Support from an NSF/USDA/DOE postdoctoral training grant to A.G. is gratefully acknowledged. A.G. also wishes to thank Prof. Govindjee for valuable discussions. C.I.W.-D.P.B. Publication No. 1197.     

Regulation of electron transport in maize mesophyll chloroplasts: The relationship between chlorophyll a fluorescence quenching and O2 evolution

The relationship between the redox state of the primary electron acceptor of photosystem II (Q_A) and the rate of O₂ evolution in isolated mesophyll chloroplasts from Zea mays L. is examined using pulse-modulated chlorophyll a fluorescence techniques. A linear relationship between photochemical quenching of chlorophyll fluorescence (q_Q) and the rate of O₂ evolution is evident under most conditions with either glycerate 3-phosphate or oxaloacetate as substrates. There appears to be no effect of the transthylakoid pH gradient on the rate of electron transfer from photosystem II into Q_A in these chloroplasts. However, the proportion of electron transport occurring through cyclic-pseudocyclic pathways relative to the non-cyclic pathway appears to be regulated by metabolic demand for ATP. The majority of non-photochemical quenching in these chloroplasts at moderate irradiances appeared to be energy-dependent quenching.Abbreviations and symbols PSII photosystem II - Fm maximum fluorescence obtained on application of a saturating light pulse - Fo basal fluorescence recorded in the absence of actinic light (i.e. all PSII traps are open) - Fv Fm-Fo - q_Q photochemical quenching - q_NP non-photochemical quenching - q_E energy-dependent quenching of chlorophyll fluorescence     

Amino acid deletions in loop C of the chlorophyll a-binding protein CP47 alter the chloride requirement and/or prevent the assembly of photosystem II

The chlorophyll a-binding protein CP47 directs excitation energy to the reaction center of photosystem II (PSII) during oxygenic photosynthesis and has additional structural and functional roles associated with the PSII water-oxidizing complex. Oligonucleotide-directed mutagenesis was employed to study loop C of CP47 (approximately Trp-162 to Gly-197) which faces the thylakoid lumen. Five short amino acid deletion strains, (S169–P171), (Y172–G176), (G176–P180), (E184–A188) and (F190–N194), were created that span this domain. The deletion between Gly-176 and Pro-180, located around the middle of loop C, produced an obligate photoheterotroph that could not assemble functional PSII centers. The deletions in mutants (S169–P171) and (Y172–G176) reduced PSII levels to 20% of the control and thus impaired photoautotrophic growth. In contrast, mutants (E184-A188) and (F190–N194) were photoautotrophic even though the number of photosystems was decreased by 50%. All PSII complexes assembled in the deletion strains had an increased susceptibility to photoinactivation and deletion of Glu-184 to Ala-188 prevented photoautotrophic growth under chloride-limiting conditions. Furthermore, the removal of the extrinsic PSII-O, PSII-U and PSII-V proteins from mutants (E184–A188) and (F190–N194) reduced the rates of oxygen evolution and, in the strains lacking either the PSII-O or PSII-V proteins, also increased the photoautotrophic doubling times. These effects were greater in mutant (E184–A188) than in mutant (F190–N194) and the order of importance for the removal of the extrinsic proteins was found to be PSII-V PSII-O > PSII-U.     

Participation of β-carotene in reactivation of PSI of heptane-extracted spinach chloroplasts

A carotenoid requirement for photosystem I activity in spinach chloroplasts using extraction-reconstitution technique has been investigated. The transfer of electron from N,N,N,N-tetramethyl-p-phenylene diamine through the chloroplast photosystem to methyl viologen dye or to NADP⁺ was used as an assay of photosystem I activity. Extraction of lyophilized spinach chloroplasts with heptane at near 0°C removed almost all -carotene and reduced photochemical activities associated with photosystem I to a low level (about 15% of the original activity). Reconstitution of the extracted chloroplasts with -carotene completely restored photosystem I activity. The maximum rate of methyl viologen photoreduction in reconstituted chloroplasts occurred at an -carotene/chlorophyll molar ratio of 0.5. Cyclic phosphorylation mediated by phenazine methosulphate was partially restored. Xanthophylls (lutein, neoxanthin, violaxanthin), as components of chloroplast membranes, were not able to replace -carotene in reconstitution of chloroplasts and had essentially no effect on restoring photoreactions. On the basis of the P700/total chlorophyll ratio it can be assumed that extraction of lyophilized chloroplasts with heptane do not affect photosystem I reaction centre. Therefore it is possible that -carotene, removed during heptane extraction and belonging mainly to the antenna pigment pool of photosystem I, is effective in the restoration of photosystem I activity.Abbreviations chl chlorophyll - DCIP 2,6-dichlorophenolindophenol - DCMU 3-(3,4-dichlorophenyl)-1,1-dimethylurea - EPR electron paramagnetic resonance - MV methyl viologen - PMS phenazine methosulphate - PQA plastoquinone A - PS I photosystem I - PS II photosystem II - TMPD N,N,N',N'-tetramethyl-p-phenylene diamine - Tricine N-tris(hydroxymethyl)methyglycine. D-1, D-10, D-50, D-144 represent chloroplast subfractions sedimented at 1000 × g, 10,000 g, 50,000 × g and 144,000 × g - s supernatant This paper is a partial fulfillment of the requirements for the Ph.D. degree of A.T. at Maria Curie-Skodowska University, Lublin.     

Adoptions expérimentales de larves entre des fourmis de genres différents (II):Myrmica laevinodis Nylander etAnergates atratulus Schenck

Résumé Nous avons fait élever des larves d'Anergates atratulus par des ouvrières deMyrmica laevinodis à 22°C. Pour y parvenir, il n'est pas utile de faire hivernerensemble les larves d'Anergates et les ouvrières deMyrmica. La présence de larves autochtones n'empêche pas lesMyrmica d'élever des larves d'Anergates. Dans toutes les expériences lesMyrmica ont été soumises au fridavant de recevoir des larves d'Anergates. Aucune reine deMyrmica n'a été utilisée dans ces expériences.Sur les 64 larves d'Anergates que nous avons utilisées, 38 se sont transformées en imagos. C'est au début de l'adoption et au moment des métamorphoses que périrent la plupart des 26Anergates perdus. Les femelles vécurent en général 2 ou 3 jours et cherchèrent très tôt à quitter le nid natal. Les mâles vécurent 2 à 3 semaines.

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Summary Larvae ofAnergates atratulus were experimentally reared by workers ofMyrmica laevinodis, at 22°C. An overwintering of both larvae ofAnergates and workers ofMyrmica is not necessary for the success of that experiment. The presence of larvae ofMyrmica does not keep theMyrmica from rearing larvae ofAnergates. The workers ofMyrmica have been cooled, in all the experiments, before receiving larvae ofAnergates. No queen ofMyrmica have been used in that experiments.38 of the 64 larvae ofAnergates used became imagos. Most of the 26 lostAnergates died at the beginning of the adoption and during the metamorphosis. The females lived generally 2 or 3 days and tried, very early, to leave their native nest. The males lived 2 or 3 weeks.

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Anergates atratulus Myrmica laevinodis, 22 . bmecme Anergates Myrmica. Myrmica Anergates. Myrmica Anergates. Myrmica . 64 Anergates , 38 . 26 Anergates 2 3 . 2 3 .

     

Selective photobleaching of PSI-related chlorophylls in heat-stressed pea chloroplasts

Measurements of electron transport activity point to the occurrence of major changes in the organisation of the photosynthetic apparatus of heat-stressed chloroplasts. One of the consequences of these changes is shown to be a greatly increased susceptibility of chlorophyll to photobleaching. Despite the fact that the threshold temperature for this photobleaching coincides closely with that for the inhibition of PSII activity, the bleached components were found to be specifically associated with PSI. This increased susceptibility of PSI pigments to photobleaching is shown to be a direct consequence of an interruption of the flow of reductants from PSII to PSI that would normally protect PSI from photooxidation.Abbreviations PSI photosystem I - PSII photosystem II - chl a chlorophyll a - chl b chlorophyll b - LHCP chlorophyll a/b light-harvesting protein - CP₁ P700-chlorophyll a protein - DCMU 3-(34 dichlorophenyl)-11-dimethylurea - DCPIP dichlorophenolindophenol - Fecy potassium ferricyanide - MV methyl viologen Biochemistry Department, King's College (KQC), University of London     

Normal expression of the viral gene N interferes with growth of bacteriophage lambda in Escherichia coli 15T-.

Summary Growth of and of some lambdoid phages is considerably inhibited on strain 3057 derived from E. coli 15T^-. Mutants of which overcome this inhibition map in gene N. Some of these hty mutants are temperature sensitive for growth on E. coli K12. Thus plating of on strain 3057 allows one to isolate temperature sensitive N mutants. The hty mutants produce less than normal N activity as judged by their low efficiency of plating on a nus ^- host and by the extended latent period of some of them on normal hosts. The inability of strain 3057 to propagate can be at least partially reversed by addition of thymidine to the medium and the growth difference between hty and in 3057 increases with decreasing thymidine concentration. The amount of DNA produced by in 3057 at low thymidine concentration is lower than that produced by hty under the same conditions. Only a small percentage of the DNA produced by in 3057 is packaged into viable phage particles. This suggests that not only produces less DNA in 3057 than hty but that an important part of the DNA in 3057 is in a form which can not be packaged or which is noninfective for other reasons. A hypothesis is discussed that hty mutations enable to grow on E. coli 15T^- at low thymidine concentration because they lead to reduction in the number of single strand nicks in the DNA by reducing the intracellular endonuclease activity. Under permissive conditions conditional lethal N mutants are favored for growth on 3057 over N ⁺ which confirms the idea that N activity or the activity of a gene under N control interferes with growth in 3057 at low thymidine concentration.     

Adoptions expérimentales de larves entre des fourmis de genres différents:Leptothorax nylanderi Förster etSolenopsis fugax Latreille

Résumé En l'absence de son propre couvain,Solenopsis fugax a élevé des larves deLeptothorax nylanderi, à la température de 22°C. Les ouvrières deSolenopsis détruisirent une partie de ces larves mais nourrirent celles qu'elles épargnèrent; ces dernières grossirent lentement pendant cinq à six mois, sans atteindre le stade prénymphe. Lorsque les ouvrières deS. fugax et les larves deL. nylanderi furent soumises ensemble à un hivernage préalable, elles donnèrent les mêmes résultats que sans hivernage. La présence d'une jeune reine deSolenopsis fut défavorable aux larves deLeptothorax.Inversement,L. nylanderi fut capable d'élever, à la température de 22°C, des larves deS. fugax et de les amener jusqu'au stade adulte. En présence de leurs propres larves, les ouvrières deL. nylanderi détruisirent tapidement toutes les larves deS. fugax introduites dans leur nid. D'autre part, un jeune couvain deLeptothorax remplaçait plus ou moins rapidement les larves deLeptothorax enlevées au préalable; sa présence était alors défavorable au développement des larves deSolenopsis. Un hivernage en début d'expérience fut plutôt favorable auxS. fugax, de même que la présence d'une reine féconde deLeptothorax. LesSolenopsis ainsi obtenus n'ont pas vécu plus de sept semaines. Ils étaient tous de caste ouvrière et de taille très petite.

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Summary When its own eggs and larvae missed,Solenopsis fugax bred larvae ofLeptothorax nylanderi, at a temperature of 22°C. TheSolenopsis workers killed some of this larvae and fed the others; these slowly grew bigger during five or six months but never reached the pre-pupa stage. The result was the same if the workers ofS. fugax and the larvae ofL. nylanderi overwintered together or not at all. A youngSolenopsis queen being there was noxious to the larvae ofLeptothorax.On the contrary,L. nylanderi has been able to breed larvae ofS. fugax up to the imago stage, at a temperature of 22°C. When its own larvae were in the nest, together with larvae ofS. fugax, the workers ofL. nylanderi killed the larvae ofS. fugax. On the other hand, new eggs and young larvae ofLeptothorax had to replace, more or less quickly, the larvae which had been taken away, and that was noxious to the growth ofSolenopsis larvae. An overwintering at the beginning of the experiment was rather favourable toS. fugax as was the presence of a fecundLeptothorax queen. TheSolenopsis thus obtained lived no longer than seven weeks. They all were workers and very small.

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S. Fugax L. Nylanderi 22° . Leptothorax , , , , . . S. Fugax Leptothorax.,L. Nylanderi 22° S. Fugax . L. Nylanderi ( )Leptothorax ; S. Fugax Solenopsis, Leptothorax. S. Fugax . .

     

Amino acid deletions in the cytosolic domains of the chlorophyll a-binding protein CP47 slow QA − oxidation and/or prevent the assembly of Photosystem II

The Photosystem II (PSII) core antenna chlorophyll a-binding protein, CP47, contains six membrane-spanning -helices separated by five hydrophilic loops: A–E. To identify important hydrophilic cytosolic regions, oligonucleotide-directed mutagenesis was employed to introduce short segment deletions into loops B and D, and the C-terminal domain. Four strains carrying deletions of between three and five residues were created in loop B. Two strains, with deletions adjacent to helices II and III, did not assemble PSII; however, the mutants (F123–D125) and (R127–S131) remained photoautotrophic with near wild-type levels of assembled reaction centers. In contrast, all deletions introduced into loop D, connecting helices IV and V, failed to assemble significant levels of PSII and were obligate photoheterotrophic mutants. However, deletions in the C-terminal domain did not prevent the assembly of PSII reaction centers although the mutant (S471–T473), with a deletion adjacent to helix VI, exhibited retarded Q_A ^– oxidation kinetics and the PSII-specific herbicide, atrazine, bound less tightly in the (S471–T473) and (F475–D477) strains. Deletions in the C-terminal domain also created mutants with large protein aggregates that were recognized by an antibody raised against the PSII reaction center D1 protein. Low-temperature fluorescence emission spectra of photoautotrophic strains carrying deletions in either the C-terminal domain or loop B did not provide evidence for impaired energy transfer from the phycobilisomes to the PSII reaction center. The data therefore suggest an important structural role for loop D in the assembly of PSII and a potential interaction between the C-terminal domain of CP47 and the PSII reaction center that, when perturbed, results in photoinduced protein aggregates involving the D1 protein.     

Genetic analysis of brown planthopper resistance in twenty varieties of rice,Oryza saliva L.

Summary The inheritance of resistance to brown planthopper, Nilaparvata lugens (Stol.), of 20 rice cultivars was studied. Single dominant genes that are allelic to Bph 3 condition the resistance in cultivars Ptb 19, Gangala (Acc. 7733), Gangala (Acc. 15207), Horana Mawee, Kuruhondarwala, Mudu Kiriyal and Muthumanikam. Single recessive genes that are allelic to bph 4 govern the resistance in cultivars Gambada Samba, Heenhoranamawee, Hotel Samba, Kahata Samba, Kalukuruwee, Lekam Samba, Senawee, Sulai, Thirissa and Vellai Illankali. The resistance in Ptb 33, Sudu Hondarwala, and Sinna Sivappu is governed by one dominant and one recessive gene which segregate independently of each other. The dominant resistance genes in these cultivars appear allelic to either Bph 1 or Bph 3. Similarly, the recessive genes in these cultivars seem allelic to either bph 2 or bph 4. Further investigations are needed to conclusively determine the allelic relationships of resistance genes in Ptb 33, Sudu Hondarwala and Sinna Sivappu.     

The action of lipases on chloroplast membranes I. The release of plastocyanin from galactolipase-treated thylakoid membranes

Bean chloroplasts treated with galactolipase (lipolytic acyl hydrolase) isolated from bean leaves showed an inhibition of photosystem I activity as measured by methyl viologen-mediated oxygen uptake and NADP⁺ photoreduction. This inhibition was partially reversed by exogenous plastocyanin added to galactolipase-treated thylakoid membranes. Galactolipase released substantial amounts of endogenous plastocyanin (about 40%) from bean chloroplasts. The results are discussed with regard to the localization of plastocyanin in thylakoid membranes.Abbreviations chlf chlorophyll - DCMU 3-(2,4-dichlorophenyl)-1,1-dimethylurea - DGDG digalactosyldiacylglycerol - MGDG monogalactosyldiacylglycerol - MV methyl viologen - NADP⁺ nicotinamide dinucleotide phosphate - PC phosphatidylcholine - PG phosphatidylglycerol - PE phosphatidylethanolamine - PI phosphatidylinositol - SQDG sulphoquinovosyldiacylglycerol - SDS sodium dodecyl sulphate - TMPD N,N,N,N-tetramethyl-p-phenylenediamine - Tricine N-Tris-(hydroxymethyl)-methylglycine - Tris Tris-(hydroxymethyl)-aminomethane     

Combined effect of cytochalasin a and adenosine triphosphate onPhysarum polycephalum

Summary Physarum polycephalum microplasmodia exposed to 1.6×10^–5 M cytochalasin A evidenced intracellular cytoplasmic condensation, slow contraction, and eventual breaks at discrete surface areas, within one hour. Other cytochalasins tested (CB or CD) did not substitute for CA. CA effects on plasmodia were not abolished by immediate washing or media replacement. In nutrient medium, CA plus ATP (375 M) produced within minutes herniation (blebbing) and plasmodial disruption. The order of addition of reagents was important; ATP added simultaneously with or prior to CA stimulated the phenomenon, whereas initial addition of CA resulted in no such dynamic response. Several other nucleotides (e.g., AMP, cAMP) could substitute for ATP; however, such changes were not observed with 5-adenylylimidodiphosphate. Blebbing was not abolished in the presence of 2,4-dinitrophenol. In minimal medium, it was best stimulated by simultaneous addition of Ca⁺⁺ and Mg⁺⁺. Preincubation of CA with L-cysteine or with -mercaptoethanol negates its individual or nucleotide-combined effects. Yet, 10^–5 M ethacrynic acid, a sulfhydryl-reactive liposoluble drug, in the presence of ATP does not mimic the blebbing response. These observed effects, which take place at or near the plasmodial surface, presumably reflect acceleration of normal contractile processes inPhysarum. Abbreviations CA cytochalasin A - CB cytochalasin B - CD cytochalasin D - AMP adenosine 5-monophosphate - ADP adenosine 5-diphosphate - ATP adenosine 5-triphosphate - di-butyryl-cAMP di-butyryl-cyclic adenosine 35-monophosphate - di-butyrylcGMP di-butyryl-cyclic guanosine 35-monophasphate. This work was supported by a grant (AI-11902) from the U.S. Public Health Service.     

Über die chemische Natur der Reserve-Polysaccharide in Acetabularia-Chloroplasten

Summary The reserve polysaccharides in chloroplasts of several species of Acetabularia have been identified as starch.The starch granules in situ as well as the isolated and purified particles stain with Lugol-reagent. They show the characteristic birefringence.Acid hydrolysis and degradation by -amylase followed by acid hydrolysis showed that the starch is composed only of glucose units.The statements of Vanden Driessche and Bonotto (1967) concerning the inulin character of the reserve polysaccharides in Acetabularia chloroplasts need correction.     

Kinetics of the flash-induced electrochromic absorbance change in the presence of background illumination. Turnover rate of the electron transport. I. Isolated intact chloroplasts

We investigated the flash-induced electrochromic absorbance change, A ₅₁₅, of isolated intact chloroplasts in continuous monochromatic background light of different intensities and wavelengths. From the variation of the amplitude of A ₅₁₅ in background illumination the steady-state turnover time of electron transport was found to be around 100 msec and the slowest process could be assigned to a photosystem 1 driven cycle. The change of pH induced by nigericin, ATP, or ADP did not modify substantially the turnover time.In contrast to earlier observations the slow rise (10 msec) of A ₅₁₅ in untreated chloroplasts persists also at high-intensity background illumination exciting both photosystems. The proportion of the slow rise of A ₅₁₅ in nigericin-treated chloroplasts increases in the presence of background light. This result on the slow rise is discussed in terms of two different models existing in the literature.     

Purification and characterization of the 5′ → 3′ exonuclease domain-deleted Thermus filiformis DNA polymerase expressed in Escherichia coli

The gene encoding 5 3 exonuclease domain-deleted Tfi DNA polymerase, named 5 3 Exo^– Tfi fragment, from Thermus filiformis was expressed in Escherichia coli under the control of the tac promoter on a high-copy plasmid, pJR. The expressed enzyme was purified 27-fold with a 19% yield and a specific activity of 2621 U mg^–1 protein. The 5 3 exonuclease domain of Tfi DNA polymerase was removed without significant effect on enzyme activity and stability. PCR conditions for the 5 3 Exo^– Tfi fragment were more tolerant to the buffer composition as compared to the full-length enzyme.