Role of chloroplast photosystems II and I in apoptosis of pea guard cells.

Received Revision received We investigated the CN--induced apoptosis of guard cells in epidermal peels isolated from pea (Pisum sativum L.) leaves. This process was considerably stimulated by illumination and suppressed by the herbicides DCMU (an inhibitor of the electron transfer between quinones Q(A) and Q(B) in PS II) and methyl viologen (an electron acceptor from PS I). These data favor the conclusion drawn by us earlier that chloroplasts are involved in the apoptosis of guard cells. Pea mutants with impaired PS I (Chl-5), PS II (Chl-I), and PS II + PS I (Xa-17) were tested. Their lesions were confirmed by the ESR spectra of Signal I (oxidized PS I reaction centers) and Signal II (oxidized tyrosine residue Y(D) in PS II). Destruction of nuclei (a symptom of apoptosis) and their consecutive disappearance in guard cells were brought about by CN- in all the three mutants and in the normal pea plants. These results indicate that the light-induced enhancement of apoptosis of guard cells and its removal by DCMU are associated with PS II function. The effect of methyl viologen preventing CN--induced apoptosis in wild-type plants was removed or considerably decreased upon the impairment of the PS II and/or PS I activity.

[Characteristics of infection of plants and their cultured tissue with cyanobacterial-bacterial symbiotic associations]. / Osobennosti infitsirovaniia rastenii i ikh kul'tiviruemykh tkanei assotsiativnymi tsianobakterial'no-bakterial'nymi kompleksami mikrosimbiontov.

The infection of tobacco, nightshade, rice plants, and their tissue cultures with the cyanobacteria-bacteria symbiotic associations (CBSA) isolated from natural syncyanoses (the ferns Azolla pinnata and Azolla sp. and the cycad Encephalartos ferox) was studied. The inoculation of the intact plants or their cuttings with CBSA led to the colonization of the plant roots, stems, and leaves by cyanobacteria and their bacterial symbionts (referred to as satellite bacteria, SB). The sites of the long-term contact of plant organs with cyanobacteria were characterized by the formation of copious slime. On the roots of infected plants, one could observe the callus growth of cortical parenchyma cells and the formation of pseudonodules, in which SB cells gradually accumulated. In mixed cultures of plant callus tissues and the CBSA isolated from the ferns A. pinnata and Azolla sp., the callus tissue specifically influenced the growth of the CBSA components, causing (depending on the plant species and strain) either their balanced growth, or their cyclic growth, or the predominant growth of one of the CBSA components (either cyanobacteria or satellite bacteria). This phenomenon is proposed to be used for the dissociation of stable multicomponent natural symbiotic complexes and the selection of their particular components.

Hydrogen peroxide inhibits photosynthetic electron transport in cells of cyanobacteria.

The effect of H2O2 on photosynthetic O2 evolution and photosynthetic electron transfer in cells of cyanobacteria Anabaena variabilis and Anacystis nidulans was studied. The following experiments were performed: 1) directly testing the effect of exogenous H2O2; 2) testing the effect of intracellular H2O2 generated with the use of methyl viologen (MV); 3) testing the effect of inhibiting intracellular H2O2 decomposition by salicylic acid (SA) and 3-amino-1,2,4-triazole (AT). H2O2 inhibited photosynthetic O2 evolution and light-induced reduction of p-benzoquinone (BQ) + ferricyanide (FeCy) in the Hill reaction. The I50 value for H2O2 was ~0.75 mM. Photosynthetic electron transfer in the cells treated with H2O2 was not maintained by H2O2, NH2OH, 1,5-diphenylcarbazide, tetraphenylboron, or butylated hydroxytoluene added as artificial electron donors for Photosystem (PS) II. The H2O --> CO2, H2O --> MV (involving PSII and PSI) and H2O --> BQ + FeCy (chiefly dependent on PSII) electron transfer reactions were inhibited upon incubation of the cells with MV, SA, or AT. The N,N,N,N-tetramethyl-p-phenylenediamine --> MV (chiefly dependent on PSI) electron transfer was inhibited by SA and AT but was resistant to MV. The results show that H2O2 inhibits photosynthetic electron transfer. It is unlikely that H2O2 could be a physiological electron donor in oxygenic photosynthesis.

Hydrogen peroxide inhibits the growth of cyanobacteria.

H2O2 at concentrations of 10(-5)-10(-4) M suppresses phototrophic growth of Anacystis nidulans and Anabaena variabilis in dialysis culture. The growth of the cyanobacteria resumed after a long adaptation period. In batch cultures, the growth of A. nidulans and A. variabilis was suppressed after one-time addition of 10(-2)and 10(-3)-10(-2) M H2O2, respectively. Inducing intracellular H2O2 formation by adding methylviologen, vitamin K3, or phenazine methosulfate suppresses the growth of both cyanobacteria. The catalase inhibitor salicylic acid suppresses the growth of A. nidulans and A. variabilis at a concentration of 5.10(-3) M. The data suggest an inhibitory effect of H2O2 on the growth of the cyanobacteria. H2O2 is unlikely to serve as an electron donor during photosynthesis.

Inhibition of photosynthetic oxygen evolution by protonophoric uncouplers.

The protonophoric uncouplers carbonyl cyanide m-chlorophenylhydrazone (CCCP), 2,3,4,5,6-pentachlorophenol (PCP) and 4,5,6,7-tetrachloro-2-trifluoromethylbenzimidazole (TTFB) inhibited the Hill reaction with K3[Fe(CN)6] (but not with SiMo) in chloroplast and cyanobacterial membranes (the I50 values were approx. 1-2, 4-6 and 0.04-0.10 µM, respectively). The inhibition is due to oxidation of the uncouplers on the Photosystem II donor side (ADRY effect) and their subsequent reduction on the acceptor side, ie. to the formation of a cyclic electron transfer chain around Photosystem II involving the uncouplers as redox carriers. The relative amplitude of nanosecond chlorophyll fluorescence in chloroplasts was increased by DCMU or HQNO and did not change upon addition of uncouplers, DBMIB or DNP-INT; the HQNO effect was not removed by the uncouplers. The uncouplers did not inhibit the electron transfer from reduced TMPD or duroquinol to methylviologen which is driven by Photosystem I. These data show that CCCP, PCP and TTFB oxidized on the Photosystem II donor side are reduced by the membrane pool of plastoquinone (Qp) which is also the electron donor for K3 [Fe(CN)6] in the Hill reaction as deduced from the data obtained in the presence of inhibitors. Inhibition of the Hill reaction by the uncouplers was maximum at the pH values corresponding to the pK of these compounds. It is suggested that the tested uncouplers serve as proton donors, and not merely as electron donors on the oxidizing side of Photosystem II.

Interaction of a synthetic peptide of the interferon alpha 2 C-terminal part with human blood leukocytes. II. Effect on protein tyrosine phosphorylation.

Tyrosine phosphorylation in human blood lymphocytes was studied as a function of stimulation with concanavalin A (ConA) and treatment of the cells with interferon alpha 2 (IFN alpha 2) and/or an IFN-derived C-terminal synthetic peptide 2438 (amino acid residues 124-138). Both IFN alpha 2 and the peptide 2438 decreased the level of protein tyrosine phosphorylation in the ConA-stimulated cells. In unstimulated cells, IFN alpha 2 increased, and the peptide 2438 decreased the level of the tyrosine phosphorylation. A possible correlation of these effects with stimulation of cell proliferation is discussed.

Synthetic peptide with antiproliferative activity: a short C-terminal fragment of the human interferon alpha-2 molecule.

The biological activity of six synthetic peptides of the 124-144 region of the human interferon alpha-2 (IFN alpha-2) molecule was studied. Peptides were examined for their ability to inhibit mitogen induced proliferation of human blood cells in vitro. Only the peptide corresponding to the amino acid sequence 124-138 (2438) possessed IFN-like antiproliferative activity. Other tested synthetic peptides did not affect cell proliferation in this experimental system. As with the native IFN alpha-2 molecule, the inhibitory effect of the peptide 2438 was dose-dependent. On simultaneous addition of peptide 2438, antiproliferative activity of IFN alpha-2 was enhanced. Direct cytotoxic effects of synthetic peptide 2438 were not revealed. These results suggest that a synthetic peptide corresponding to the 124-138-amino acid sequence of the human IFN alpha-2 molecule serves as a cytostatic agent.

Interaction of a synthetic peptide of the interferon alpha-2 C-terminal part with human blood leukocytes. Binding to peripheral blood mononuclear cells.

A biologically active synthetic peptide, 2438, representing the 124-138 amino acid sequence of the human interferon alpha-2 (IFN alpha-2) molecule, which is known to possess IFN-like antiproliferative activity, specifically binds to human blood leukocytes. Scatchard plots reveal two different Kd values, for the 'low' and 'high' affinity binding. The interaction of the 125I-labelled peptide 2438 with the cells is not impaired by human IFN alpha-2 or cholera toxin.

Introduction of a nitrogen-fixing cyanobacterium into tobacco shoot regenerates.

Tobacco (Nicotiana tabacum L.) shoots associated with the nitrogen-fixing cyanobacterium Anabaena variabilis Kütz. (ATCC 29413) were regenerated in mixed cultures of tobacco callus and the cyanobacterium. The cyanobacteria were localized inside the tissues as well as on the surface of regenerated shoots, formed heterocysts, and were capable of acetylene reduction.

[Superoxide dismutase in Clostridium butyricum spores]. / Superoksiddismutaza c sporakh Clostridium butyricum.

Superoxide dismutase was found for the first time in the spores of the anaerobic bacterium Clostridium butyricum. The prosthetic group of the enzyme was shown to contain iron. The enzyme was demonstrated to be highly thermostable.

Interaction between photosynthetic and respiratory electron-transfer chains in the membranes of Anabaena variabilis.

The rate of CO2- and p-benzoquione-dependent photosynthetic O2 evolution by Anabaena variabilis cells remained unaltered and the rate of O2 uptake observed after switching off the light (endogenous respiration) was enhanced by a factor of 6-8 when the O2 concentration was increased from 200 to 400 µM. Photosystem-I-linked O2 uptake and respiration of the cells incubated with ascorbate and N,N,N'N'-tetramethyl-p-phenylenediamine was not appreciable influenced by the O2 concentration. 2-Iodo-6-isopropyl-3-methyl-2',4,4'-trinitrodiphenyl ether, blocking electron transfer at the plastoquinone level, suppressed O2 evolution and had no influence on endogenous respiration. 2-n-Heptyl-4-hydroxyquinoline-N-oxide, an inhibitor of electron transfer between photosystems II and I, as well as the cytochrome-oxidase inhibitors N 3 (-) , CN(-) and NH2OH, caused a 35-50% retardation of endogenous respiration and blocked photosynthetic O2 evolution. The molar ratio of cytochromes b6, f, c-553, aa3 and photosystem-I reaction centers in the isolated membranes equalled approx. 2:1:2:0.7:2. It is inferred that endogenous respiration of A. variabilis cells is inhibited by the light-induced electron flow through both photosystems at the level of the plastoquinone-plastocyanin-oxidoreductase complex.

[Effect of petroleum hydrocarbons on the viability of cyanobacteria in association with oil-oxidizing bacteria]. / Vliianie neftianykh uglevodorodov na zhiznesposobnost' tsianobakterii v assotsiatsii s nefteokisliaiushchimi bakteriiami.

An important aspect in the problem of interactions between microorganisms in the conditions of oil pollution is how to preserve the viability of phototrophic organisms if active oil-oxidizing microflora is present in the environment. As was illustrated using a closed model ecosystem, the association 'cyanobacteria--oil-oxidizing bacteria' is capable of withstanding the negative effect of oil pollution, but within the range of hydrocarbon concentrations which can be oxidized by oil-oxidizing bacteria during a very short time. The biological equilibrium in the ecosystem was maintained and the number of viable cells of the phototrophic component in the ecosystem increased if the oil-oxidizing bacteria started to function at the same time as toxic compounds commenced to produce their effect on the microorganisms.

[Effect of cyanobacteria excretions and cell biomass on hydrocarbon-oxidizing mycobacteria]. / Vliianie vydelenii i kletochnoi biomassy tsianobakterii na uglevodorodokisliaiushchie mikobakterii.

The presence of cyanobacterial cells and their exocellular excretions in an aqueous ecosystem stimulated biodegradation of diesel fuel. As was established using the technique of complete factor analysis, nitrogen addition to the medium and the presence of cyanobacterial cells in it are important for the growth of oil-oxidizing bacteria, while exocellular excretions of the cells are not sufficient for such a growth. The mycobacterial growth depended, to a certain extent, on the age of cyanobacterial cultures.

[Conditions for cyanobacteria L-transformation]. / Izuchenie uslovii L-transformatsii u tsianobakterii.

Anabaena variabilis and Chlorogloea fritschii can easily form L-like colonies that are characterized by their appearance and the morphology of component structures. The colonies consist of morphological elements typical of the L-variants of chemoheterotrophic bacteria: filaments, "grains", ring-shaped cells, etc. Data are presented pertinent to the functional activity of the photosynthetic apparatus of these organisms subjected to L-transformation.

[Comparative study of the oxygen reduction in photosystem II of the cyanobacteria, Anacystis nidulans and Anabaena variabilis]. / Sravitel'noe izuchenie protsessa vosstanovleniia kisloroda v fortosisteme II u tsianobakterii Anacystis nidulans i Anabaena variabilis.

Oxygen reduction in the photosystem II (PS II) of thylakoid membranes from the cyanobacteria Anacystis nidulans and Anabaena variabilis was studied in the system SiMo + DCMU in whose presence competitive electron transport to SiMo and O2 in possible. The reagents of the Mehler reaction were used; these reagents activate oxygen uptake by interacting with the reduced forms of oxygen (malonate and oxalate with O2; glyoxylate and catalase + ethanol with H2O2). The use of the reagents as shown that there was a considerable electron transport to O2 which decreased the rate of SiMo reduction and visible oxygen evolution. Oxygen was reduced to O2 and H2O2 in the photosystem II of A. nidulans whereas practically no generation of H2O2 was observed in the photosystem II of A. variabilis. Malate was found to be capable of activating oxygen uptake in the PS II of the cyanobacteria by interacting with O2. Oxalate was capable of this interaction only in the membranes of A. variabilis, but not in the membranes of A. nidulans where it competed with water as an electron donor. A decrease in SiMo reduction and oxygen evolution in A. nidulans in the presence of glycolate was due to oxidation of glyoxylate which was formed in the course of enzyme-catalyzed oxidation of glycolate by the membranes possessing the activity of glycolate oxidase, and the subsequent interaction of glyoxylate with H2O2. SiMo reduction by the cyanobacterial membranes and by the spheroplasts of A. variabilis, in contrast to the chloroplasts of higher plants, did not decrease in the presence of DCMU, but went on at a linear rate until the substrate was completely exhausted. The role of reduced O2 forms in metabolism of a phototrophic cell is discussed.

[KMnO4-induced change in the chemiluminescence of Pseudomonas aeruginosa cells after their preliminary interaction with pyocyanine]. / Izmenenie vyzvaemoi KMnO4 khemiliuminestsentsii kletok Pseudomonas aeruginosa posle ikh predvaritel'nogo vzaimodeistviia s piotsianinom.

Pyocyanin was capable of interacting with the cells when it was added to the cell suspensions of a Pseudomonas aeruginosa P. culture producing the pigment and a mutant that did produce pyocyanin. As a result, the intensity of chemiluminescence induced by KMnO4 in the cells decreased. Pyocyanin inhibited the chemiluminescence of the parent strain and mutant cell homogenates and their fractions, with an exception of the fraction of the mutant cell walls with which it did not react. The character of pyocyanin interaction with the cells of Ps. aeruginosa P. was shown to depend on the conditions of the cultural incubation.

[Chromophore composition and nature of the absorption spectra of phycobiliproteins]. / Khromofornyi sostav i priroda spektrov gogloshcheniia fikobiliprotendov.

It was shown that phycobiliproteins are native pigment complexes, in which the protein quaternary structure is responsible for the aggregation of the chromophore groups covalently bound to the apoprotein. The main factor determining the structure of the phycobiliprotein absorption spectra is the excitone interaction of the chromophores, in which the number of bands in the spectrum is proportional to the number of interacting chromophores. In accordance with the number of bands (4) in the phycocyanobilin spectrum, i. e. chromophore of allophycocyanin and C-phycocyanin, and with the number of chromophores covalently linked to each one of the apoprotein molecules (2 for allophycocyanin and 3 for C-phycocyanin) their absorption spectra split into eight (2 X 4) and twelve (3 X 4) and twelve (3 X 4) bands, respectively. It is concluded that allophycocyanin is a native aggregate--dimer, while C-phycocyanin is a trimer of phycocyanobilin.