Crop tolerance to saline sprinkling water

Summary Crops sprinkled with saline irrigation water are subject to foliar salt absorption and injury as well as to injury from soil salinity. Yield reductions caused by soil salinity alone are well documented, and data are presented here for 71 agricultural crops. Factors affecting these data and their applicability to sprinkler-irrigated crops are discussed. Although foliar injury has been observed with many sprinkled crops, particularly tree crops, essentially no information is available to predict yield losses as a function of the salt concentration of the irrigation water. Salinity thresholds for sprinkling-induced foliar injury are estimated for some crops; however, climatic conditions greatly affect the onset and degree of injury. Managment strategies that minimize sprinkling injury are mentioned.     

Effect of saline acclimation on body water and sodium compartmentalization in Pekin ducks (Anas platyrhynchos)

The compartmentalization of body fluids was measured in individual Pekin ducks ( Anas platyrhynchos) drinking freshwater and after sequential acclimation to 300 mM NaCl and 400 mM NaCl. Total body water, extracellular fluid volume, plasma volume and exchangeable sodium pool were measured using (3)H(2)O, [(14)C]-polyethylene glycol, Evans Blue dye, and (22)Na dilution, respectively. Following acclimation to 300 mM NaCl, body mass decreased, but total body water and total exchangeable sodium pool were unaltered. Na and water were redistributed from the extracellular fluid (interstitial fluid) compartment into the intracellular fluid compartment. Following further acclimation to 400 mM NaCl, body mass, total body water and intracellular fluid volume decreased, but exchangeable sodium pool and extracellular fluid volume were unchanged. Our results suggested that, when Pekin ducks drink high but tolerable salinities, they maintain total body water, but redistribute Na(+) and water from interstitial fluid to the intracellular fluid compartment. When stressed beyond their ability to maintain total body water, they lose water from the intracellular fluid.     

Effects of botulism on ducks drinking saline water

Mallard (Anas platyrhynchos) ducklings (2 wk old) were given water from natural saline wetlands or fresh water as drinking water for 1 or 2 wk prior to, and after, receiving material containing Clostridium botulinum type C toxin. Water with conductivity ranging from 3,460 to 6,690 mu mhos/cm had no detectable effect on the occurrence or severity of clinical signs of botulism. Ducks drinking water with conductivity of 7,130 mu mhos/cm for 1 wk prior to receiving toxin had more severe clinical signs and greater mortality than did birds drinking fresh water. Ducks given the same water for 2 wk prior to receiving toxin did not differ from the controls in response to toxin. Fewer ducks in groups drinking the most saline water tested (conductivity = 13,500 mu mhos/cm) had clinical signs of botulism than in groups drinking fresh water.     

Peroxisomes contribute to biosynthesis of extracellular glycolipids in fungi

Many microorganisms secrete surface‐active glycolipids. The basidiomycetous fungus Ustilago maydis produces two different classes of glycolipids, mannosylerythritol lipids (MEL) and ustilagic acids (UAs). Here we report that biosynthesis of MELs is partially localized in peroxisomes and coupled to peroxisomal fatty acid degradation. The acyltransferases, Mac1 and Mac2, which acylate mannosylerythritol with fatty acids of different length, contain a type 1 peroxisomal targeting signal (PTS1). We demonstrate that Mac1 and Mac2 are targeted to peroxisomes, while other enzymes involved in MEL production reside in different compartments. Mis‐targeting of Mac1 and Mac2 to the cytosol did not block MEL synthesis but promoted production of MEL species with altered acylation pattern. This is in contrast to peroxisome deficient mutants that produced MELs similar to the wild type. We could show that cytosolic targeting of Mac1 and Mac2 reduces the amount of UA presumably due to competition for overlapping substrates. Interestingly, hydroxylated fatty acids characteristic for UAs appear in MELs corroborating cross‐talk between both biosynthesis pathways. Therefore, peroxisomal localization of MEL biosynthesis is not only prerequisite for generation of the natural spectrum of MELs, but also facilitates simultaneous assembly of different glycolipids in a single cell.     

Salt tolerance of Agaricus bisporus in relation to water stress and toxicity of sodium ions

Using NaCl or polyethylene glycol (PEG) solutions to progressively decrease the external osmotic potential of the peat casing of the growing medium used to culture the mushroom Agaricus bisporus resulted in proportionately decreased yields of sporophores. Over the range of -0.07 to -0.37 MPa, the extent of decrease in yield was similar with both types of osmoticum. However, with further decrease in external osmotic potential (from -0.37 to -0.62 MPa) there was a further proportional decrease in sporophore yield with PEG but a complete suppression of sporophore production with NaCl. Treatments with both NaCl and PEG decreased the concentrations of P, Mg, K, Fe and Mn, but not N and Cu, in sporophore dry matter. Treatment with NaCl solutions increased the concentrations of Na and CI ions in sporophore dry matter and decreased the concentration of Ca; PEG solutions had no effect. Ion toxicity associated with excessive accumulation of Na and C1 ions, or ionic imbalance associated with the concomittant decrease in Ca ions appear to be additional factors to osmotic stress in decreasing yield of sporophores when the growing medium becomes highly saline. The critical concentration of NaCl which caused 10% reduction in sporophore yield was 28 mM; A. bisporus is, therefore, moderately salt-sensitive.     

Surface wax esters contribute to drought tolerance in Arabidopsis

Waxes are components of the cuticle covering the aerial organs of plants. Accumulation of waxes has previously been associated with protection against water loss, therefore contributing to drought tolerance. However, not much information is known about the function of individual wax components during water deficit. We studied the role of wax ester synthesis during drought. The wax ester load on Arabidopsis leaves and stems was increased during water deficiency. Expression of three genes, WSD1, WSD6 and WSD7 of the wax ester synthase/diacylglycerol acyltransferase (WS/DGAT or WSD) family was induced during drought, salt stress and abscisic acid treatment. WSD1 has previously been identified as the major wax ester synthase of stems. wsd1 mutants have shown reduced wax ester coverage on leaves and stems during normal or drought condition, while wax ester loads of wsd6, wsd7 and of the wsd6wsd7 double mutant were unchanged. The growth and relative water content of wsd1 plants were compromised during drought, while leaf water loss of wsd1 was increased. Enzyme assays with recombinant proteins expressed in insect cells revealed that WSD6 and WSD7 contain wax ester synthase activity, albeit with different substrate specificity compared with WSD1. WSD6 and WSD7 localize to the endoplasmic reticulum (ER)/Golgi. These results demonstrated that WSD1 is involved in the accumulation of wax esters during drought, while WSD6 and WSD7 might play other specific roles in wax ester metabolism during stress.     

Postprandial recruitment of neutrophils may contribute to endothelial dysfunction

Atherosclerosis is a low-grade inflammatory disease involving leukocytes, lipids, and glucose leading to endothelial dysfunction. Since activation of neutrophils by triglycerides and glucose has been described in vitro, we hypothesized that the postprandial phase is an inflammatory state affecting leukocytes, possibly contributing to endothelial dysfunction. We measured postprandial blood leukocyte counts, cytokines, hydroperoxides (HPOs), and flow-mediated vasodilation (FMD) in eight healthy males (age 23 +/- 2 years) after a FAT (50 g/m2) and GLUCOSE challenge (37.5 g/m2), a combination of both (MIXED test), and after WATER. All tests, except WATER, resulted in significantly impaired FMD (10% reduction) between t = 1 h and t = 3 h, accompanied by a significant increase of neutrophils (59% after FAT and 28% after GLUCOSE and MIXED), total plasma HPOs (15 to 31% increase), and plasma interleukin-8 (IL-8) (50-130% increase). WATER did not affect FMD, neutrophils, HPOs, or IL-8. Lymphocytes increased gradually in all tests (40-70% increase at t = 10 h compared with t = 0; P < 0.005), paralleling a gradual 3- to 5-fold interleukin-6 increase. Monocyte and erythrocyte counts did not change in any test. In conclusion, the neutrophil increment during postprandial lipemia and glycemia with concomitant IL-8 and HPO increases may contribute to endothelial dysfunction. Lymphocyte increment is a nonspecific diurnal process. Postprandial intravascular inflammatory changes may be relevant for the pathogenesis of atherosclerosis.     

Molecular mimicry may contribute to pathogenesis of ulcerative colitis

Ulcerative colitis (UC) is a chronic inflammatory bowel disease with mucosal inflammation and ulceration of the colon. There seems to be no single etiological factor responsible for the onset of the disease. Autoimmunity has been emphasized in the pathogenesis of UC. Perinuclear anti-neutrophil cytoplasmic antibodies (pANCA) are common in UC, and recently two major species of proteins immunoreactive to pANCA were detected in bacteria from the anaerobic libraries. This implicates colonic bacterial protein as a possible trigger for the disease-associated immune response. Autoantibodies and T-cell response against human tropomyosin isoform 5 (hTM5), an isoform predominantly expressed in colon epithelial cells, were demonstrated in patients with UC but not in Crohn's colitis. We identified two bacterial protein sequences in NCBI database that have regions of significant sequence homology with hTM5. Our hypothesis is that molecular mimicry may be responsible for the pathogenesis of UC.     

AFLP analysis of genetic diversity and relationship among some Chinese domestic ducks and wild ducks

The amplified fragment length polymorphic(AFLP)technique was used to analyze the genome DNA polymorphism among 8 breeds of domestic ducks and 2 species of wild ducks.Nine of the 17 selected primers pairs gave reproducible polymorphic DNA amplification bands.The amplified bands ranged from 44 to 83 per primer pair.Of the 513 AFLP markers obtained.498 were polymorphic.The proportion of polymorphic loci was 97.1%.The genetic distance(D)and similarity coefficients(GS)were calculated based on the polymorphic data.Between domestic ducks D ranged from 0.331 to 0.589,while between domestic ducks and the wild ducks,it ranged from 0.298 to 0.520(vs.Anas Platyrhynchos)and from 0.316 to 0.522(vs.A.Poecilorhyncha),respectively.The variance analysis showed no significant difference between the two groups of data,which indicated that both mallard and spot-billed ducks made contributions to domestic duck evolution.A dendrogram was constructed according to the D value.     

AFLP analysis of genetic diversity and relationship among some Chinese domestic ducks and wild ducks

The amplified fragment length polymorphic (AFLP) technique was used to analyze the genome DNA polymorphism among 8 breeds of domestic ducks and 2 species of wild ducks. Nine of the 17 selected primers pairs gave reproducible polymorphic DNA amplification bands. The amplified bands ranged from 44 to 83 per primer pair. Of the 513 AFLP markers obtained, 498 were polymorphic. The proportion of polymorphic loci was 97.1%. The genetic distance (D) and similarity coefficients (GS) were calculated based on the polymorphic data. Between domestic ducks D ranged from 0.331 to 0.589, while between domestic ducks and the wild ducks, it ranged from 0.298 to 0.520 (vs. Anas Platyrhynchos) and from 0.316 to 0.522 (vs. A. Poecilorhyncha), respectively. The variance analysis showed no significant difference between the two groups of data, which indicated that both mallard and spot-billed ducks made contributions to domestic duck evolution. A dendrogram was constructed according to the D value. __________ Translated from Journal of Xiamen University (Natural Science), 2005, 44(5): 729–733 [译自: 厦门大学学报 (自然科学版), 2005, 44(5): 729–733]     

Glomerular filtration rate in saline acclimated ducks,gulls and geese

• 1.1. Glomerular filtration rate was estimated by measurement of cloacal excretion of intramuscularly injected ¹⁴C PEG in fresh water and sea water acclimated Mallards, Anas platyrhynchos, Canada Geese, Branta canadensis, and Glaucous-winged Gulls, Larus glaucescens.
• 2.2. GFR (ml/min kg) of FW Mallards was 3.3 ± 1.8 (5); FW geese, 1.2 ± 0.1 (2) and FW gulls, 1.9 ± 0.4(4).
• 3.3. Acclimation to SW did not affect the GFR of ducks, but increased the GFR of geese, 2.2 ± 0.1 (2) (P < 0.0005) and gulls, 4,0 ± 0.3 (5) (P < 0.005).

     

Redistribution of cyclic GMP in response to sodium butyrate in colon cells

The effect of butyrate on the response to guanylin and Escherichia coli heat-stable enterotoxin, STa, was assessed in T84 cells and Caco-2 cells, cultured colon cell lines possessing the guanylyl cyclase C which is the receptor for these peptides. Butyrate treatment of these cells resulted in an apparent increase in cyclic GMP (cGMP) accumulation when the cGMP content of cells and the supernatant medium was measured. Butyrate treatment did not change the guanylyl cyclase activity or (125)I-STa binding parameters in T84 cells, but the butyrate effect was completely blocked by cycloheximide. Butyrate did not have any effect on STa-stimulated cGMP accumulation in COS cells transfected with the human or porcine GC-C. Further experiments showed that butyrate treatment caused a large increase in the cGMP released into the culture medium, and in cells grown in polarized fashion in Transwell inserts, cGMP efflux was predominantly from the basolateral surface of the cell; intracellular cGMP was actually lowered by butyrate treatment. Exposure of T84 cells to butyrate had no effect on the disposition of cyclic AMP generated in response to forskolin. The effects of butyrate on cGMP were reversible within 24 h of butyrate withdrawal. In colon cells, butyrate treatment induced a previously undescribed, cGMP-specific efflux mechanism which lowered intracellular cGMP and elevated extracellular cGMP in response to peptide agonists such as guanylin and STa.     

Newly identified genes contribute to vanillin tolerance in Saccharomyces cerevisiae

Exploring the mechanisms of tolerance in microorganisms to vanillin, which is derived from lignin, will benefit the design of robust cell factories that produce biofuels and chemicals using lignocellulosic materials. Our objective was to identify the genes related to vanillin tolerance in Saccharomyces cerevisiae. We investigated the effects on vanillin tolerance of several genes that have site mutations in the highly vanillin-tolerant strain EMV-8 compared to its parental line NAN-27. The results showed that overexpression of GCY1, a gene that encodes an aldo-keto reductase that also has mRNA-binding activity, YPR1, a paralog of GCY1 that encodes an aldo-keto reductase, PEX5, a gene that encodes a peroxisomal membrane signal receptor and MBF1, a gene that encodes a multiprotein bridging factor increase the specific growth rates (μ) by 49%, 41%, 44% and 48 %, respectively, in medium containing 6 mmol l⁻¹ vanillin. Among these gene products, Gcy1p and Ypr1p showed NADPH-dependent and NAD(P)H-dependent vanillin reductase activity, respectively. The reductase-inactive mutant Gcy1p^Y56F also increased vanillin tolerance in S. cerevisiae, suggesting that other mechanisms exist. Although TRS85 and PEX5, genes for which the mRNAs are binding targets of Gcy1p, were shown to be related to vanillin tolerance, both the mRNA and protein levels of these genes were not changed by overexpression of GCY1. The relationship between the mRNA-binding activity of Gcy1p and its positive effect on vanillin tolerance is still not clear. Finally, we found that the point mutation D112A in Mbf1p, which disrupts the binding of Mbf1p and the TATA element-binding protein (TBP), did not decrease the positive effect of Mbf1p on vanillin tolerance. This indicates that the binding of Mbf1p and TBP is not necessary for the positive effect on vanillin tolerance mediated by Mbf1p. We have successfully identified new genes related to vanillin tolerance and provided novel targets that can be used to improve the vanillin tolerance of S. cerevisiae. Moreover, we have extended our understanding of the proteins encoded by these genes.     

Dynamic simulations of the molecular conformations of wild type and mutant xanthan polymers suggest that conformational differences may contribute to observed differences in viscosity

Xanthan gum is an exopolysaccharide secreted by the bacterium Xanthamonas campestris whose ability to make solutions viscous at low concentrations and over a pH and temperature range have generated much interest in both academic and industrial environments. Mutant Xanthamonas strains have been derived that produce xanthan gums with an altered or variant subunit chemical structure and different measured viscosities when compared with the wild type (wt) form of the polymer. Two variant gums were targeted as potentially interesting in this study, these being the nonacetylated tetramer (natct; and the acetylated tetramer (atet), which both lack a side-chain terminal mannose residue and in one case (natet) lacks an acetate group on an internal mannose residue. Solutions of these tetrameric gums possess viscosities higher (natet) and lower (atet) than the wt gum, and therefore we have attempted to determine whether these molecules possess unique conformational preferences when compared with the wt and with each other. In this manner we can initiate an understanding of how a polysaccharide's conformation contributes to its solution properties. The GEGOP software permits a sampling of the static and dynamic equilibrium states of carbohydrate molecules, and this software was employed to calculate equilibrium states of representative oligosaccharides with chemical structures representative of xanthan-like molecules. Energy minimization techniques revealed similar local minima for all three molecules. Some of these minima are comprised of elongate backbone conformations (A type) in which side chains fold onto backbone surfaces. Other minima with A backbones possessed side chains in less intimate backbone contact especially when calculations were performed with a low dielectric constant. This phenomenon was particularly pronounced in the wt molecule where an increased number of negatively charged side-chain residues experience charge repulsion resulting in reduced side-chain-backbone contact. Metropolis Monte Carlo (MMC) dynamic simulations performed with an elevated temperature factor (1000 K) allowed a better qualitative representation of conformational space than 300 K simulations. Employing a nonhierarchical cluster analysis method (population density profile: PDP) coupled with a classification scheme, it was possible to partition resulting MMC data sets into conformational families. This analysis revealed that in simulations performed with different dielectric constant values (10, 25, and ∞) all molecules possessed primarily A-type backbones. Less elongate, more open helical backbone forms (B, C, D, J, and Flat-a) did occur during the simulations but were populated to a lesser extent. In the natet molecule significantly open helical backbones existed (E, F, G, H, and I) that did not occur in the lower viscosity wt and atet molecules. PDP clustering methods and subsequent conformational classification applied to the first residue (mannose) of the side chain permitted a determination of side-chain orientation. Comparison of all three molecules indicated a larger population of side-chain conformational families in less direct backbone contact for the wt molecule than either of the variant molecules (natet/atet) suggesting that the side chains in the wt are more flexible. Thus, a major conformational difference between the high viscosity natet. In addition, the significant difference between the higher viscosity wt and the lower viscosity atet is the increase side-chain flexibility in the wt. We hypothesize that conformational differences of this kind could form a partial explanation of the observed differences in viscosity between these xanthan-like polymers. © 1996 John Wiley & Sons, Inc.     

Maturational differences in chlorpyrifos-oxonase activity may contribute to age-related sensitivity to chlorpyrifos

Chlorpyrifos (CPF), a commonly used cholinesterase-inhibiting insecticide, is lethal at much lower doses to young animals than adults. To explain this higher sensitivity in younger animals, we hypothesized that young rats have less chlorpyrifos-oxonase (CPFOase) activity than adults. To test this hypothesis, CPFOase activity was measured in the brain, plasma, and liver of male, postnatal day 4 (PND4) and adult (PND90) Long-Evans rats. CPFOase is biochemically defined as a Ca²⁺-dependent A-esterase that hydrolyzes chlorpyrifos-oxon (CPFO), the active metabolite of CPF. No brain CPFOase activity was detected at either age. Plasma and liver CPFOase activities were markedly lower at PND4 compared to adult: PND4 plasma and liver CPFOase activities were 1/11 and 1/2 the adult plasma and liver activities, respectively. Because the K_m of CPFOase activity was high (i.e., 210–380 μM), it was important to determine if this CPFOase activity could hydrolyze physiologically relevant concentrations (i.e., nM to low μM) of CPFO. This was accomplished by comparing the shifts in the tissue acetylcholinesterase (AChE) IC₅₀ for CPFO in the presence or absence of CPFOase activity. One would expect an increase in the “apparent” IC₅₀ if CPFOase hydrolyzes substantial amounts of CPFO during the 30 minutes the tissue is preincubated with the CPFO. In the adult, both plasma and liver AChE apparent IC₅₀ values were higher in the presence of CPFOase activity, suggesting that the CPFOase in those tissues was capable of hydrolyzing physiologically relevant concentrations of CPFO within 30 minutes. In young animals, however, there was less of a shift in the IC₅₀ curves compared to the adult, confirming that the young animal has less capacity than the adult to detoxify physiologically relevant concentrations of CPFO via CPFOase. © 1997 John Wiley & Sons, Inc. J Biochem Toxicol 11: 279–287, 1997.