Catabolic activity of two phosphoric diester hydrolases in wheat leaves inoculated with brown rust,Puccinia recondita

Changes in total phospholipids and activities of two phosphoric diester hydrolases,i.e. phospholipase C and phospholipase D have been studied in inoculated wheat leaves of 25-day old plants, interacting differentially with three races of brown rust,Puccinia recondita, during early stages of pathogenesis. With progressive rust iafection the lipids and phospholipids were found to decrease in all the three interactions except at later stages (48 h and 72 h) in race 104-interaction. However, total phospholipids at various stages were found to be higher in resistant interaction (race 63) as compared to the other two interactions. An initial increase in activities of phospholipase C and D in all the three interactions was followed by a decline at the intermediate stages which continued in case of phospholipase C activity while a reverse trend was observed in phospholipase D activity towards later stages of infection. Further the enzymatic activities at various stages were found to be higher in the susceptible and intermediate interactions (with races 77 and 104 respectively) as compared to the resistant interaction.     

Kinetic and thermodynamic behaviour of wall-bound peroxidase from wheat leaves infected with stripe rust

We have identified two types of peroxidases (POX), one ionically and one covalently bound to the particulate fraction, in stripe rust-infected and -uninfected wheat (Triticum aestivum L.) leaves. The cell walls contained a high level of POX, of which 73–76% was extractable by 1% NaCl and 24–26% by 5 mM EDTA in infected and non-infected leaves of HD 2329. The NaCl-released POX constituted the predominant fraction. Both NaCl- and EDTA-extracted POX exhibited maximum activity at pH 5.0 and had a K _m (enzyme–substrate affinity measure) value of 1.61–1.70 and 1.64–1.67 mM, respectively, with o-dianisidine as the substrate. The V _max (maximum catalytic rate) in the two extractions ranged between 7.06–7.45 and 6.65–7.82 μmol min⁻¹ g⁻¹ fresh weight. A temperature optimum of 50°C was observed for both the NaCl- and EDTA-released fractions. The two POX fractions showed a differential response to metal ions, suggesting their distinctive nature. Sodium azide inhibited POX activity markedly, which suggested the presence of heme as a prosthetic group. Inhibition of wall-bound POX by iodine and the regeneration of activity by mercaptoethanol suggested the involvement of cysteine in the active site of the enzyme. These two forms showed greater differences in terms of thermodynamic properties, such as the energy of activation (E _a) and enthalpy change (ΔH), while entropy (ΔS) and free energy changes were similar. The results further show that pathogen infection of the leaves of this susceptible wheat cultivar induces an increase in the activity and kinetics of POX, which may be critical in the response of the plant cell to infection.     

Effects of ozone and peroxyacetyl nitrate on polar lipids and Fatty acids in leaves of morning glory and kidney bean

To compare the effects of ozone and peroxyacetyl nitrate (PAN) on leaf lipids, fatty acids and malondialdehyde (MDA), morning glory (Pharbitis nil Choisy cv Scarlet O'Hara) and kidney bean (Phaseolus vulgaris L. cv Gintebo) plants were exposed to either ozone (0.15 microliter per liter for 8 hours) or PAN (0.10 microliter per liter for up to 8 hours). Ozone increased phospholipids in morning glory and decreased in kidney bean at the initial stage (2-4 hours) of exposure, while it scarcely changed glycolipids, the unsaturated fatty acids, and MDA in both plants. A large reduction of glycolipids occurred 1 day after ozone exposure in both plants. PAN caused marked drops in phospholipids and glycolipids in kidney bean at relatively late stage (6-8 hours) of exposure, while it increased phosphatidic acid and decreased the unsaturated fatty acids, an increase which was accompanied by a large increase in MDA. These results suggest that ozone may not directly oxidize unsaturated fatty acids at the initial stage of exposure, but may alter polar lipid metabolism, particularly phospholipids. On the other hand, PAN may abruptly and considerably degrade phospholipids and glycolipids by peroxidation or hydrolysis at the late stage of exposure. The present study shows that ozone and PAN affect polar lipids in different manners.     

Effects of three substituted cadaverines on infection of barley with powdery mildew and brown rust

Spraying barley plants with three substituted cadaverines (0.5 mmol/l) resulted in substantial reductions in both powdery mildew and brown rust infections. Post-inoculatory sprays were more effective than pre-inoculatory sprays and addition of cadaverine (0.5 mmol/l to the treatments partially reversed the effects of the cadaverine analogues. Cadaverine alone had no effect on powdery mildew or rust infection.     

Growth and yield of lentil and wheat inoculated with three Glomus isolates from Saskatchewan soils

The vesicular-arbuscular mycorrhizal fungi (VAMF) Glomus clarum (Nicol. and Schenck) isolate NT4, G. mosseae (Nicol. and Gerd.) Gerd. and Trappe isolate NT6 and G. versiforme (Karst.) Berch isolate NT7 coexist in wheat field soils in Saskatchewan. This study assessed the response of lentil (Lens esculenta L.) and wheat (Triticum aestivum L.) to monospecific and mixed cultures of these VAMF isolates. Seedlings were inoculated with 100 spores of a VAMF isolate, or an equal mixture of spores of two isolates, and grown in a sterile soil mix in a growth chamber. Both crops responded differently to these different VAMF isolates. In the case of lentil, G. clarum NT4 was more effective than G. mosseae NT6 and G. versiforme NT7, and significantly increased (P<0.05) the shoot dry weight (43%) and grain yield (57%) compared with the uninoculated control. There was a significant positive correlation between the percentage of VAMF colonized roots and shoot dry weight (r=0.672^***) and shoot phosphorus concentration (r=0.608^***) of lentil. In the case of wheat, G. clarum NT4 had no effect on shoot dry weight, but produced significant (P<0.08) increases in grain yield (12%) and the phosphorus concentration of the shoot and grain. Although G. clarum NT4 and G. mosseae NT6 both produced similar levels of VAM colonization in wheat, the only response of wheat to isolate NT6 was an increase in plant height at harvest. The efficacy of G. clarum NT4 on both crops appeared to be related to its ability to produce more arbuscular colonization than G. mosseae NT6. Dual inoculation of seedlings with G. clarum NT4 and G. mosseae NT6 resulted in competition between these two isolates. This was evident from a comparison of plant shoot dry weight and grain yield, and VAMF spore production on the two crops inoculated either with isolate NT4 alone or in combination with NT6. G. mosseae NT6 reduced the efficacy of G. clarum NT4 by 16% when dual inoculated on lentil, but had no effect when the host was wheat. Based on spore production, it was found that G. clarum NT4 was more competitive than G. mosseae NT6 when dual inoculated on lentil or wheat. Isolate NT4 produced ca. 2000 and 500 spores/ 100 g substrate, respectively, in the lentil and wheat pots, which was approximately 2–3 times more spores than those produced by isolate NT6 with either crop. When the plants were dual inoculated, there was a 15–19% reduction in spore production by G. clarum NT4 and a 50–70% decrease in spore production by G. mosseae NT6. Our results show that G. clarum NT4 was more competitive and effective in its ability to colonize and increase the growth and yield of lentil and wheat than G. mosseae NT6 or G. versiforme NT7. The relative performance of isolate NT4 with different host plants suggests that this VAMF isolate exhibits a host preference for lentil.     

Induced chitinase activity in resistant wheat leaves inoculated with an incompatible race of Puccinia striiformis f. sp. tritici,the causal agent of yellow rust disease

Chitinase specific activity was measured spectrophotometrically in wheat leaf tissues during the compatible and incompatible interactions with Puccinia striiformis f. sp. tritici, the causal agent of yellow rust disease. The wheat cultivar, Federation^* 4/Kavkaz, was inoculated with virulent (134E134A+) or avirulent (4EOA+) races of P. striiformis f. sp. tritici in the first leaf stage. The results showed that chitinase activity pattern was similar in both compatible and incompatible interactions up to 72 hrs after inoculation. However, the specific activity increased rapidly in the incompatible reaction thereafter. In susceptible reaction, chitinase activity gradually declined after 72 hrs post-inoculation reaching a level similar to that in the control plants two weeks after inoculation. Chitinase specific activity in resistance response was at least three times greater than that in the susceptible reaction two weeks following the inoculation. Electrophoresis of native polyacrylamide gel impregnated with 0.1% (w/v) glycol chitinas the substrate revealed the presence of eight chitinase isoforms with relative electrophoretic mobility (R_m) values ranging from 0.11 to 0.64 in the resolving gel. This revised version was published online in June 2006 with corrections to the Cover Date.     

Phytopathological and molecular genetic identification of brown rust resistance genes in common wheat accessions with alien genetic material

Brown rust resistance genes were sought in 23 resistant common wheat accessions with alien genetic material of Aegilops speltoides, Ae. triuncialis, and Triticum kiharae from the Arsenal collection. The genes were identified by common phytopathological tests and PCR analysis with STS markers directed to the known Lr genes. None of the methods identified the resistance genes in two accessions. In the other accessions, the combination of the two methods broadened the spectrum of detectable genes and, in some cases, allowed double verification of the presence of a resistance gene. Most accessions proved to contain several brown rust resistance genes, combining juvenile and adult plant ones. The accessions were found to contain gene combinations that ensured field resistance and immunity under the conditions of the Non-Chernozem region (Lr13 + Lr10 and Lr12 + Lr34). Accessions with alien genetic material contained a unique combination of five or six resistance genes. Since the accessions were rich in brown rust resistance genes, including effective ones, and carried rare combinations of these genes, they were proposed as donors to be universally employed in breeding for immunity in all regions of Russia.     

Fatty acid composition and content of individual lipid fractions in adipose and muscle tissue of albino rats with alloxan diabetes

A study was made of the fatty acid composition and the content of triglycerides, phospholipids and nonesterified fatty acids (NFA) in adipose and muscle tissues of rats with alloxan diabetes. The concentration of NFA in alloxan diabetes was found to be considerably reduced in both adipose and muscle tissues. Meanwhile the content of NFA and phospholipids did not experience any substantial changes. The fatty acid composition of triglycerides of the tissues under study was characterized by considerable alterations under diabetes.     

Expression of a gene for plastid ω-3 fatty acid desaturase and changes in lipid and fatty acid compositions in light- and dark- grown wheat leaves

The leaves of monocotyledonous plants create a developmental sequence of cells and plastids from the base to the apical portion. We investigated fatty-acid and lipid compositions in successive leaf sections of light- and dark-grown wheat (Triticum aestivum L. cv. Chihoku) seedlings. The most notable change in the fatty acid composition was the increase of linolenic acid (18:3) with maturation of leaf cells, which occurred both in light- and dark-grown leaf tissues. In light-grown leaves, the increase of 18:3 with maturation was mainly attributed to the increase of monogalactosyldiacylglycerol (MGD) and also to the increase of the 18:3 level of MGD. In dark-grown leaves, the increase of 18:3 in the leaf apex was caused by the increase of the levels of MGD and digalactosyldiacylglycerol (DGD) and also by the increase of the 18:3 levels of within these two lipids. Since MGD and DGD are mainly found in plastid membranes, these findings indicate that both the synthesis of galactolipids and the formation of 18:3 these lipids take place during plastid development. The plastid ω-3 fatty acid desaturase is responsible for the formation of 18:3 in plastid membrane lipids. To investigate the regulation of desaturation, we isolated a gene for wheat plastid ω-3 fatty acid desaturase (TaFAD7). The mRNA level of TaFAD7 in light-grown leaves was much higher than that in dark-grown leaves. During the greening of etiolated leaves the level of TaFAD7 mRNA increased significantly, accompanied by an increase of the 18:3 level of total fatty acids. On the other hand, the levels of TaFAD7 mRNA were almost the same in all the leaf sections of both light- and dark-grown leaf tissues. These results suggest that the effect of the expression of the TaFAD7 gene on the increase of the 18:3 level is different between the leaf development under continuous light- or dark-conditions and the light-induced greening process of etiolated leaves. The increase of 18:3 content of MGD (or MGD and DGD) with maturation is apparently regulated not solely by the level of TaFAD7 mRNA.     

Structure of a specialized acyl carrier protein essential for lipid a biosynthesis with very long-chain Fatty acids in open and closed conformations

The solution nuclear magnetic resonance (NMR) structures and backbone (15)N dynamics of the specialized acyl carrier protein (ACP), RpAcpXL, from Rhodopseudomonas palustris, in both the apo form and holo form modified by covalent attachment of 4'-phosphopantetheine at S37, are virtually identical, monomeric, and correspond to the closed conformation. The structures have an extra α-helix compared to the archetypical ACP from Escherichia coli, which has four helices, resulting in a larger opening to the hydrophobic cavity. Chemical shift differences between apo- and holo-RpAcpXL indicated some differences in the hinge region between α2 and α3 and in the hydrophobic cavity environment, but corresponding changes in nuclear Overhauser effect cross-peak patterns were not detected. In contrast to the NMR structures, apo-RpAcpXL was observed in an open conformation in crystals that diffracted to 2.0 ? resolution, which resulted from movement of α3. On the basis of the crystal structure, the predicted biological assembly is a homodimer. Although the possible biological significance of dimerization is unknown, there is potential that the resulting large shared hydrophobic cavity could accommodate the very long-chain fatty acid (28-30 carbons) that this specialized ACP is known to synthesize and transfer to lipid A. These structures are the first representatives of the AcpXL family and the first to indicate that dimerization may be important for the function of these specialized ACPs.     

Levels of linoleic acid and saturated and monounsaturated fatty acids in selected lipid fractions of the serum and platelets in patients with coronary arterial disease

The levels of serum fatty acids in the serum and in the serum fractions of cholesterol esters (ECH) and triglycerides (TG) and the levels of these acids in these fractions of platelets were compared in healthy controls and in patients with clinically manifested coronary arterial disease. Decreased level of linoleic acid was found in the serum and in the ECH fraction of the serum in the patients, with a rise in the level of palmitic acid in the ECH fraction of the serum of these patients. The level of linoleic acid in the ECH and TG platelet fractions in these patients was not different from that in the healthy controls, while in the platelet TG fraction of the patients the level of palmitoleic acid was raised, and the level of oleic acid was increased in the platelet ECH fraction.     

Evolution of C6, C8 and C10 acids and their ethyl esters in cells and musts during fermentation with threeSaccharomyces cerevisiae races

Summary The evolution of the cell and must contents of three short-chain fatty acids (C₆, C₈ and C₁₀) and their ethyl esters during fermentations withSaccharomyces cerevisiae racescerevisiae, bayanus andcapensis were studied. The former is a fermentative yeast and the last two are flor film yeasts. The acid concentrations in the musts increased throughout the alcoholic fermentations, and maximum cell concentrations of the fatty acids were reached after 48 h of fermentation. Maximum ester concentrations in the cells were attained after 48–72 h of fermentation. In the musts, ethyl octanoate and ethyl decanoate reached a peak also at this point, and ethyl hexanoate after 10 days. After 134 days,S. cerevisiae racecapensis formed a thick flor film whileS. cerevisiae racebayanus developed a thin film andS. cerevisiae racecerevisiae formed no film. At this point, acid contents remained constant in the wines produced byS. cerevisiae racescerevisiae andbayanus, and decreased in those obtained with racecapensis. The ethyl ester contents tended to decrease with the exception of ethyl decanoate in the fermentations carried out byS. cerevisiae racescerevisiae andbayanus.     

Study on the components of tolerance and identification of resistance gene Lr34 with molecular tool to the wheat brown rust disease (Puccinia triticina) in the promising lines

Brown rust disease is one the most important fungal disease of wheat in Iran. Using of resistance cultivars is the best control method of disease. In this study, genetic resistance of 82 promising lines was evaluated in green house condition. Their resistance components included Infection Type, Latent Period, Postule Size and Postule Density in the randomised complete block design with two replications. In the molecular level for lines with corresponding adult plant resistance Lr34 gene, PCR process by means of STS marker and the primer Lr34/Yr18 was done. The results of variance analysis obtained implicated a significant difference in the 1% probable. The minimum value detected as ?0.88 to the Gorgan isolate and the maximum value for ?0.94 to Ahwaz isolate. In the cluster analysis related to two isolates, lines were divided to four groups composed. The presence of gene Lr34 was proved into the two genotypes “ER-S8–90” and “ER-N3–90”.     

Polar lipid fatty acids,LPS-hydroxy fatty acids,and respiratory quinones of three <Emphasis Type="Italic">Geobacter</Emphasis> strains,and variation with electron acceptor

The polar lipid fatty acids, lipopolysaccharide hydroxy-fatty acids, and respiratory quinones of Geobacter metallireducens str. GS-15, Geobacter sulfurreducens str. PCA, and Geobacter bemidjiensis str. Bem are reported. Also, the lipids of G. metallireducens were compared when grown with Fe³⁺ or nitrate as electron acceptors and G. sulfurreducens with Fe³⁺ or fumarate. In all experiments, the most abundant polar lipid fatty acids were 14:0, i15:0, 16:1ω7c, 16:1ω5c, and 16:0; lipopolysaccharide hydroxy-fatty acids were dominated by 3oh16:0, 3oh14:0, 9oh16:0, and 10oh16:0; and menaquinone-8 was the most abundant respiratory quinone. Some variation in lipid profiles with strain were observed, but not with electron acceptor. D. C. White: Deceased.     

Activities of hydrolases and their protein inhibitors in wheat leaves treated with salicylic and jasmonic acids and infected with <Emphasis Type="Italic">Septoria nodorum</Emphasis> strains differing in aggressiveness

The effect of infection with fungus Septoria nodorum strains differing in aggressiveness on the activity of hydrolytic enzymes (amylases and proteinases) and their protein inhibitors in the leaves of Triticum aestivum L. pretreated with salicylic and jasmonic acids was studied. It was shown that aggressive Septoria nodorum strains accelerated development, caused intensive necrotic reaction on the wheat leaves, increased the production of amylases and proteinases, and decreased the activity of their protein inhibitors. Salicylic and jasmonic acids altered the activity of the “hydrolase-inhibitor” complex, which indicated the possibility of regulation of the activity (content) of this group of compounds via exogenous effects, including the treatment of plants with inducers of resistance of various natures.     

Production of manganese peroxidase and organic acids and mineralization of 14C-labelled lignin (14C-DHP) during solid-state fermentation of wheat straw with the white rot fungus nematoloma frowardii

The basidiomycetous fungus Nematoloma frowardii produced manganese peroxidase (MnP) as the predominant ligninolytic enzyme during solid-state fermentation (SSF) of wheat straw. The purified enzyme had a molecular mass of 50 kDa and an isoelectric point of 3.2. In addition to MnP, low levels of laccase and lignin peroxidase were detected. Synthetic 14C-ring-labelled lignin (14C-DHP) was efficiently degraded during SSF. Approximately 75% of the initial radioactivity was released as 14CO2, while only 6% was associated with the residual straw material, including the well-developed fungal biomass. On the basis of this finding we concluded that at least partial extracellular mineralization of lignin may have occurred. This conclusion was supported by the fact that we detected high levels of organic acids in the fermented straw (the maximum concentrations in the water phases of the straw cultures were 45 mM malate, 3.5 mM fumarate, and 10 mM oxalate), which rendered MnP effective and therefore made partial direct mineralization of lignin possible. Experiments performed in a cell-free system, which simulated the conditions in the straw cultures, revealed that MnP in fact converted part of the 14C-DHP to 14CO2 (which accounted for up to 8% of the initial radioactivity added) and 14C-labelled water-soluble products (which accounted for 43% of the initial radioactivity) in the presence of natural levels of organic acids (30 mM malate, 5 mM fumarate).