The effect of the phenolic compounds exuded by pea roots in darkness on the reproduction of Rhizobium

The exudation, composition, and biological activity of the phenolic compounds (PC) of pea (Pisum sativum L.) roots in the light and darkness were studied. The roots of leguminous plants grown for 5 days in darkness exuded a smaller amount of PC that displayed a weaker stimulation of Rhizobium reproduction. Moreover, the root exudates contained antimicrobial compounds, stilbenes. It is assumed that a lower PC exudation by roots and the specific features of PC composition influencing the biological activity are among the reasons causing a delayed nodulation of legumes grown in darkness.     

The composition of fatty acids in the endosperm and embryo lipids of <Emphasis Type="Italic">Pinus sibirica</Emphasis> and <Emphasis Type="Italic">P. sylvestris</Emphasis> seeds

The fatty acid (FA) composition of storage lipids in the seed endosperms and embryos of two pine species, Pinus sibirica and P. sylvestris, and possible biosynthetic pathways of these acids were studied by the GLC method. Linoleic acid predominated in the embryo and endosperm lipids of both P. sibirica (43.5 and 42.6%) and P. sylvestris (44.8 and 46.8%); this was evidently determined by a high expression of the gene encoding stearoyl-Δ9 acyl-lipid desaturase and the fad2 gene encoding microsomal ω6 acyl-lipid desaturase. P. sibirica lipids of the embryo and endosperm contained more oleic acid (22.0 and 24.0%, respectively) than corresponding P. sylvestris lipids (18.7 and 14%). Storage lipids of conifer seeds contain Δ5-unsaturated FAs: taxoleic (18:2Δ5,9), ephedrenic (18:2Δ5,11), pinoleenic (18:3Δ5,9,12), skiadonic (18:3Δ5,11, 14), and coniferonic (18:4Δ5,9,12,15). In the endosperm and embryos of P. sylvestris, the content of pinolenic acid was higher (22.1 and 19.6%) than in P. sibirica seeds (19.1 and 18.6%).     

The effect of the phenolic compounds exuded by pea roots in darkness on the reproduction of <Emphasis Type="Italic">Rhizobium</Emphasis>

The exudation, composition, and biological activity of the phenolic compounds (PC) of pea (Pisum sativum L.) roots in the light and darkness were studied. The roots of leguminous plants grown for 5 days in darkness exuded a smaller amount of PC that displayed a weaker stimulation of Rhizobium reproduction. Moreover, the root exudates contained antimicrobial compounds, stilbenes. It is assumed that a lower PC exudation by roots and the specific features of PC composition influencing the biological activity are among the reasons causing a delayed nodulation of legumes grown in darkness.     

Lipid peroxidation in rabbit and rat visual system structures

In our work, the lipid peroxidation (LPO) in the retina, optic chiasma, and visual cortex of rat and rabbit brain was investigated. The contents of the LPO products (diene conjugates, triene conjugates, TBA-reactive products, Schiff bases) and oxidation index (calculated as 232/2 15) were similar in the retina and visual brain cortex of rats. In vivo, lipid oxidation in the optic chiasma was higher as compared with two other parts of visual tract. The similar data were obtained in our experiments with rabbit's visual tract. The sensitivity of tissues to peroxidation in vitro was studied in homogenates incubated with 0.2 mM ascorbate and 10 mkM FeSO4 for 20 min at 37 degrees C. The results of these experiments deviated from the data obtained in vivo, namely: the LPO in optic chiasma was lower than in the retina and the brain cortex. This data are in compliance with lipid composition of investigated parts of the visual tract of both animals. In our opinion, the high level of LPO in optic chiasma demonstrated in vivo is due to low antioxidants level in this part of the visual tract. Our findings also indicate that LPO in retina both in vivo and in vitro experiments are similar to those in the brain cortex and may be attributed to similar lipid composition and activity of antioxidant enzymes (such as superoxiddismutasa and glutathionereductase).     

Subunit exchange demonstrates a differential chaperone activity of calf alpha-crystallin toward beta LOW- and individual gamma-crystallins

The chaperone activity of native alpha-crystallins toward beta(LOW)- and various gamma-crystallins at the onset of their denaturation, 60 and 66 degrees C, respectively, was studied at high and low crystallin concentrations using small angle x-ray scattering (SAXS) and fluorescence energy transfer (FRET). The crystallins were from calf lenses except for one recombinant human gamma S. SAXS data demonstrated an irreversible doubling in molecular weight and a corresponding increase in size of alpha-crystallins at temperatures above 60 degrees C. Further increase is observed at 66 degrees C. More subtle conformational changes accompanied the increase in size as shown by changes in environments around tryptophan and cysteine residues. These alpha-crystallin temperature-induced modifications were found necessary to allow for the association with beta(LOW)- and gamma-crystallins to occur. FRET experiments using IAEDANS (iodoacetylaminoethylaminonaphthalene sulfonic acid)- and IAF (iodoacetamidofluorescein)-labeled subunits showed that the heat-modified alpha-crystallins retained their ability to exchange subunits and that, at 37 degrees C, the rate of exchange was increased depending upon the temperature of incubation, 60 or 66 degrees C. Association with beta(LOW)- (60 degrees C) or various gamma-crystallins (66 degrees C) resulted at 37 degrees C in decreased subunit exchange in proportion to bound ligands. Therefore, beta(LOW)- and gamma-crystallins were compared for their capacity to associate with alpha-crystallins and inhibit subunit exchange. Quite unexpectedly for a highly conserved protein family, differences were observed between the individual gamma-crystallin family members. The strongest effect was observed for gamma S, followed by h gamma Srec, gamma E, gamma A-F, gamma D, gamma B. Moreover, fluorescence properties of alpha-crystallins in the presence of bound beta(LOW)-and gamma-crystallins indicated that the formation of beta(LOW)/alpha- or gamma/alpha-crystallin complexes involved various binding sites. The changes in subunit exchange associated with the chaperone properties of alpha-crystallins toward the other lens crystallins demonstrate the dynamic character of the heat-activated alpha-crystallin structure.     

Infrared Spectroscopic Study of the Secondary Structure of Wheat,Rye, and Barley Prolamins

The secondary structure of prolamins, the storage proteins of wheat (Triticum aestivum L.), rye (Secale cereale L.), and barley (Hordeum vulgare L.), was studied by infrared (IR) spectroscopy. The secondary structure of wheat gliadin was characterized by a high content of unordered conformations of polypeptide chains (64–67%) and a low content of short -helical regions (4–5%). Elongated conformations, formed by poly-L-proline II helices (61 and 53%) and -turns (15 and 19%), predominated in rye secalins and barley hordeins. Prolamin proteins of cereal crops also contained -sheet structure regions comprising 9–12% of the polypeptide chains.     

Active oxygen species in pea seedlings during the interactions with symbiotic and pathogenic microorganisms

The level of active oxygen species (AOS)—superoxide anion radical (O ₂ ^·? ) and hydrogen peroxide (H₂O₂)—in pea (Pisum sativum L.) cultivar Marat seedlings was studied upon their inoculation with symbiotic (Rhizobium leguminosarum bv. viceae strain CIAM 1026) and pathogenic (Pseudomonas syringae pv. pisi Sackett) microorganisms. Different patterns of the changes in AOS in pea seedlings during the interactions with the symbiont and the phytopathogen were recorded. It is assumed that O ₂ ^·? and H₂O₂ are involved in the defense and regulatory mechanisms of the host plant.     

The DHHC domain: A new highly conserved cysteine-rich motif

A unique clone from a human pancreatic cDNA library was isolated and sequenced. Examination of the deduced polypeptide sequence of the clone showed a new form of cysteine-rich domain that included a region with the form of a Cys4 zinc-finger-like metal binding site followed by a complex Cys-His region. Searches of the Swiss-Protein data bank found a similar 48-residue domain in fifteen open reading frames deduced from A. thaliana, C. elegans, S. cerevisiae and S. pombe genomic sequences. The high degree of conservation of this domain (13 absolutely conserved and 17 highly conserved positions) suggests that it has an important function in the cell, possibly related to protein-protein or protein-DNA interactions. The gene recognized by the clone is is localized to human chromosome 16, and is conserved in vertebrates. The 2 Kb message is expressed in various human fetal and adult tissues. An antibody made to a peptide sequence of the deduced protein showed reactivity in immunoblots of monkey lung and retinal subcellular fractions and immunohistochemically in late fetal mouse tissues and a limited number of adult mouse tissues, including pancreatic islets, Leydig cells of the testis, and the plexiform layers of the retina.     

Effect of chronic hyperphenylalaninemia and hypoxia on the effectiveness of the alpha-ketoglutarate shunt in the brain

The effects of hypoxia and chronic hyperphenylalaninaemia (HPA) on the intensity of the alpha-oxoglutarate shunt in rat brain after injection of [5-14C]glutamate were investigated. The reaction of reducing carboxylation of alpha-oxoglutarate was shown to be the rate-limiting step for the whole pathway. The deceleration of this reaction under chronic HPA or, conversely, its increase under short-term heavy hypoxia led to a corresponding decrease or increase of fatty acid synthesis in the brain with [5-14C]glutamate as a radioactive precursor.