Degradation of aromatic compounds in plants grown under aseptic conditions

The aim of the work is to investigate the ability of higher plants to absorb and detoxify environmental pollutants - aromatic compounds via aromatic ring cleavage. Transformation of 14C specifically labelled benzene derivatives, [1-6-14C]-nitrobenzene, [1-6-(14)C]-aniline, [1-(14)C]- and [7-(14)C]-benzoic acid, in axenic seedlings of maize (Zea mays L.), kidney bean (Phaseolus vulgaris L.), pea (Pisum sativum L.) and pumpkin (Cucurbita pepo L.) were studied. After penetration in plants, the above xenobiotics are transformed by oxidative or reductive reactions, conjugation with cell endogenous compounds, and binding to biopolymers. The initial stage of oxidative degradation consists in hydroxylation reactions. The aromatic ring can then be cleaved and degraded into organic acids of the Krebs cycle. Ring cleavage is accompanied by 14CO2 evolution. Aromatic ring cleavage in plants has thus been demonstrated for different xenobiotics carrying different substitutions on their benzene ring. Conjugation with low molecular peptides is the main pathway of aromatic xenobiotics detoxification. Peptide conjugates are formed both by the initial xenobiotics (except nitrobenzene) and by intermediate transformation products. The chemical nature of the radioactive fragment and the amino acid composition of peptides participating in conjugation were identified.     

Proteolytic enzymes and trypsin inhibitors of higher plants under stress conditions

The response of the components of a protease-inhibitor system of legume and cereal crops to stress factors was studied. It was found that salinization, heavy metal ions, and phytopathogenic flora inhibit the activity of neutral, acidic, and alkaline proteases at early stages of seed germination, the degree of the inhibition of the endoprotease activity being dependent on the index of tolerance of legume and cereal crops. It was shown that, in response to unfavorable conditions, accumulation of trypsin inhibitors occurs, which is accompanied by the appearance of new protein components, as indicated by electrophoresis. The results confirm the presumption that serine protease inhibitors are involved in the response of plants to stress factors.     

Proteolytic enzymes and trypsin inhibitors of higher plants under stress conditions

The response of the components of a protease-inhibitor system of legume and cereal crops to stress factors was studied. It was found that salinization, heavy metal ions, and phytopathogenic flora inhibit the activity of neutral, acidic, and alkaline proteases at early stages of seed germination, the degree of the inhibition of the endoprotease activity being dependent on the index of tolerance of legume and cereal crops. It was shown that, in response to unfavorable conditions, accumulation of trypsin inhibitors occurs, which is accompanied by the appearance of new protein components, as indicated by electrophoresis. The results confirm the presumption that serine protease inhibitors are involved in the response of plants to stress factors.     

Changes in the acyl lipid composition of photosynthetic bacteria grown under photosynthetic and non-photosynthetic conditions

The acyl lipids and their constituent fatty acids were studied in the photosynthetic bacteria Rhodospirillum rubrum, Rhodopseudomonas capsulata and Rhodopseudomonas sphaeroides, which were grown under photosynthetic and non-photosynthetic conditions. The major lipids were found to be phosphatidylethanolamine, phosphatidylglycerol and cardiolipin in each bacterium. The two Rhodopseudomonas species also contained significant quantities of phosphatidylcholine. Other acyl lipids accounted for less than 10% of the total. On changing growth conditions from non-photosynthetic to photosynthetic a large increase in the relative proportion of phosphatidylglycerol was seen at the expense of phosphatidyl-ethanolamine. In Rhodospirillum rubrum the fatty acids of the major phospholipids showed an increase in the proportion of palmitate and stearate and a decrease in palmitoleate and vaccenate on changing growth conditions to photosynthetic. In contrast, the exceptionally high levels (>80%) of vaccenate in individual phospholipids of Rhodopseudomonas capsulata and Rhodopseudomonas sphaeroides were unaffected by changing growth conditions to photosynthetic. Analysis of the lipids of chromatophores, isolated from the three bacteria, showed that these preparations were enriched in phosphatidylglycerol. The large increase in this phospholipid, seen during growth under photosynthetic conditions, appeared, therefore, to be due to a proliferation of chromatophore membranes. Possible roles for acyl lipids in the formation and function of the photosynthetic apparatus of bacteria are discussed.     

Comparative chemical composition of the Barents Sea brown algae

Comparative study of phytochemical compositions of the most widespread brown algae species (one laminarian and four fucoid algae) from Barents Sea has been performed. A modified technique for mannitol determination in brown algae is proposed. It was revealed that fucus algae (fam. Fucaceae) contain 3% (of total dry weight) less mannitol than laminaria (Laminaria saccharina). The contents of alginic acid and laminaran in the Barents Sea fucoids are more than 10% less compared to laminaria. The alga L. saccharina contains almost two times more iodine than the species of fam. Fucaceae. The amounts of fucoidan and sum lipids in the Barents Sea fucoid algae is higher than in Laminaria saccharina (4-7% and 1-3%, respectively). In terms of contents of main biologically active compounds, fucus and laminarian algae from Barents Sea are inferior to none of the Far-Eastern species. The Barents Sea algae may become an important source of biologically active compounds.     

Comparative proteomic studies in Rhodospirillum rubrum grown under different nitrogen conditions

Forty-four differentially expressed proteins have been identified in the photosynthetic diazotroph Rhodospirillum rubrum grown anaerobic and photoheterotrophically, with different nitrogen sources, using 2D-PAGE and MALDI-TOF, from gels containing an average of 679 +/- 52 (in N(+)) and 619 +/- 37 (in N(-)) protein spots for each gel. A higher level of expression was found under nitrogen-rich growth, for proteins involved in carbon metabolism (reductive tricarboxylic acid cycle, CO(2) fixation, and poly-beta-hydroxybutyrate metabolism) and amino acid metabolism. The key enzymes RuBisCO and alpha-ketoglutarate synthase were found to be present in higher amounts in nitrogen-rich conditions. Ntr and Nif regulated proteins, such as glutamine synthetase and nitrogenase, were, as expected, induced under nitrogen-fixing conditions and glutamate dehydrogenase was down regulated. A novel 2Fe-2S ferredoxin with unknown function was identified from nitrogen-fixing cultures. In addition to differential expression, two of the identified proteins revealed variable p I values in response to the nitrogen source used.     

Comparative chemical composition of the Barents Sea brown algae

Comparative study of phytochemical compositions of the most widespread brown algae species (one laminarian and four fucoid algae) from Barents Sea has been performed. A modified technique for mannitol determination in brown algae is proposed. It was revealed that fucus algae (fam. Fucaceae) contain 3% (of total dry weight) less mannitol than laminaria (Laminaria saccharina). The contents of alginic acid and laminaran in the Barents Sea fucoids are more than 10% less compared to laminaria. The alga L. saccharina contains almost two times more iodine than the species of fam. Fucaceae. The amounts of fucoidan and sum lipids in the Barents Sea fucoid algae is higher than in Laminaria saccharina (4–7% and 1–3%, respectively). In terms of contents of main biologically active compounds, fucus and laminarian algae from Barents Sea are inferior to none of the Far-Eastern species. The Barents Sea algae may become an important source of biologically active compounds.     

Analysis of the agglutinating activity from unicellular algae

Agglutinating activity often varies both between and within the algal species assayed. However, it is difficulty to interpret such variation without further analysis. We report a statistical analysis of agglutinating activities against human, cow, sheep, and pig erythrocytes, using cell extracts from 43 taxa (strains) of freshwater microalgae. Most of the extracts agglutinated erythrocytes from at least one of the sources, but pig erythrocytes appeared to be most suitable for the detection of agglutination reactions. Chlorella cell extracts preferentially agglutinated human erythrocytes, whereas extracts of other taxa were less active against mammalian erythrocytes. Cluster analysis generated four distinct subclusters of taxa, characterized by different specificities for antigens or carbohydrate receptors on the erythrocytes. Principal component analysis further separated the agglutination characteristics of Chlamydomonas from Chlorella on the first two components. Specificity for pig erythrocytes accounted for most of the clustering or grouping of algal taxa in multivariate analysis. However, clustering or grouping patterns of Chlorella species on haemagglutinating activity resembled that based on DNA sequences, revealing a possible genetic connection of agglutinins and their biochemical characteristics in algal cells. Variability of agglutination reactions among the algae investigated is simplified and interpreted most easily using multivariate analysis.     

Codon usage in higher plants, green algae, and cyanobacteria

Codon usage is the selective and nonrandom use of synonymous codons by an organism to encode the amino acids in the genes for its proteins. During the last few years, a large number of plant genes have been cloned and sequenced, which now permits a meaningful comparison of codon usage in higher plants, algae, and cyanobacteria. For the nuclear and organellar genes of these organisms, a small set of preferred codons are used for encoding proteins. Codon usage is different for each genome type with the variation mainly occurring in choices between codons ending in cytidine (C) or guanosine (G) versus those ending in adenosine (A) or uridine (U). For organellar genomes, chloroplastic and mitochrondrial proteins are encoded mainly with codons ending in A or U. In most cyanobacteria and the nuclei of green algae, proteins are encoded preferentially with codons ending in C or G. Although only a few nuclear genes of higher plants have been sequenced, a clear distinction between Magnoliopsida (dicot) and Liliopsida (monocot) codon usage is evident. Dicot genes use a set of 44 preferred codons with a slight preference for codons ending in A or U. Monocot codon usage is more restricted with an average of 38 codons preferred, which are predominantly those ending in C or G. But two classes of genes can be recognized in monocots. One set of monocot genes uses codons similar to those in dicots, while the other genes are highly biased toward codons ending in C or G with a pattern similar to nuclear genes of green algae. Codon usage is discussed in relation to evolution of plants and prospects for intergenic transfer of particular genes.     

State 1/State 2 changes in higher plants and algae

Current ideas regarding the molecular basis of State 1/State 2 transitions in higher plants and green algae are mainly centered around the view that excitation energy distribution is controlled by phosphorylation of the light-harvesting complex of photosystem II (LHC-II). The evidence supporting this view is examined and the relationship of the transitions occurring in these systems to the corresponding transitions seen in red and blue-green algae is explored.Abbreviations CCCP carbonylcyanide-m-chlorophenylhydrazone - Chl a chlorophyll a - Chl b chlorophyll b - DAD diaminodurene - DBMIB 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone - DCCD N,N-dicyclohexyl carbodiimide - DCMU 3-(3,4-dichlorophenyl)-l,l-dimethylurea (also called diuron) - FCCP carbonylcyanide-p-trifluoromethoxyphenylhydrazone - FSBA 5-fluorosulphonylbenzoyl adenosine - kDa kilodalton - LHC-II light-harvesting Chl a/Chl b protein - PMS phenazine methosulfate - PS I photosystem I - PS II photosystem II - SDS sodium dodecyl sulfate - TPTC triphenyl tin chloride This paper follows our new instructions for citation of references—authors are requested to follow Photosynth Res 10: 519–526 (1986)—editors.     

Activity and properties of ribulose-1,5-bisphosphate carboxylase of sugarbeet plants grown under saline conditions

Activity and properties of sugar beet ( Beta vulgaris var. Polyrave) leaf ribulose-1,5-bisphosphate (RuBP) carboxylase were investigated following the exposure of plants to NaCl in the range of 45 to 270 m M for 7 days. An enhancement in RuBP carboxylase activity was found both in crude extracts and in purified preparations following plant exposure to 180 m M NaCl. Kinetic properties of the enzyme were significantly affected by salinity as determined by a 4.5 fold increase in K_m [HCO^-₃] and K_m [CO₂], and a V_max increase of 50%. Data based on polyacrylamide-gel-electrophoresis suggest that the molecular weight of the small subunit of RuBP carboxylase was reduced from 15,500 to 12,500 in plants grown under salinity. The large subunit was much less affected and no change was found in the whole enzyme. The enzyme isolated from plants exposed to salinity contained about 50% fewer titratable SH groups as compared with the control. The results indicate that in this plant, mild salt concentrations induced conformational changes in RuBP carboxylase which may be responsible for its tolerance to semi-salinity.     

Polar lipid composition of chloroplast thylakoids isolated from leaves grown under different lighting conditions

The polar acyl lipid composition was determined for samples of chloroplast thylakoids isolated from Pisum sativum plants grown at light intensities of 50 and 300 E·m^-2·s^-1 and from Aesculus hippocastanum leaves taken from shade or sun environments. Lighting conditions had no major effect on lipid class composition except for a small increase in the amount of monogalactosyldiacylglycerol relative to other lipids in low compared with high light and shade compared with sun conditions. The thylakoids from low light and shade environments also had, relative to those from high light and sun conditions, a substantial decrease in the level of trans-hexadecenoic acid in phosphatidyglycerol. In parallel with this there were lower lipid to chlorophyll ratios, higher overall fatty acid unsaturation, lower chlorophyll a to b ratios and increased relative levels of light harvesting chlorophyll a/b polypeptides as expected for an increase in the degree of thylakoid appression. With this in mind, our results on lipid class composition and content of trans-hexadecenoic acid are discussed in the context of the lateral distribution of lipids within the plane of membrane.Abbreviations DGDG digalactosyldiacylglycerol - EDTA ethylenediaminetetraacetic acid - HEPES N-2-hydroxyethylpiperazine-N-2-ethanesulfonic acid - LHC light harvesting chlorophyll a/b - MGDG monogalactosyldiacylglycerol - MPL minor phospholipids - PS1 photosystem one - PS2 photosystem two - SDS sodium dodecyl sulphate - SL sulphoquinovosyldiacylglycerol