Exogenous Glycine Betaine Reduces Drought Damage by Mediating Osmotic Adjustment and Enhancing Antioxidant Defense in <i>Phoebe hunanensis</i>

Drought stress negatively impacts growth and physiological processes in plants. The foliar application of glycine betaine (GB) is an effective and low-cost approach to improve the drought tolerance of trees. This study examined the effect of exogenously applied GB on the cell membrane permeability, osmotic adjustment, and antioxidant enzyme activities of Phoebe hunanensis Hand.-Mazz under drought stress. Two levels (0 and 800 mL) of water irrigation were tested under different applied GB concentrations (0, 50, 100, and 200 mM). Drought stress decreased the relative water content by 58.5% while increased the electric conductivity, malondialdehyde, proline, soluble proteins, soluble sugars, and antioxidant enzyme activities (superoxide dismutase, catalase, peroxidase) by up to 62.9%, 42.4%, 87.0%, 19.1%, 60.5%, 68.3%, 71.7%, and 83.8%, respectively, on the 25^th day. The foliar application of GB, especially at 100 mM, increased the relative water content of P. hunanensis leaves under drought stress. The concentration of GB from 50 to 100 mM effectively alleviated the improvement of cell membrane permeability and inhibited the accumulation of membrane lipid peroxidation products. Under drought stress, the concentrations of proline, soluble proteins, and soluble sugars in the leaves of P. hunanensis increased as the applied GB concentration was increased and the water stress time was prolonged. Exogenously applied GB decreased oxidative stress and improved antioxidant enzyme activities as compared with treatments without GB application. Furthermore, the physiological and biochemical indexes of P. hunanensis showed a certain dose effect on exogenous GB concentration. These results suggest that GB helps maintain the drought tolerance of P. hunanensis.     

Effect of synthetic surfactants and soapwort (Saponaria officinalis L.) extract on skin-mimetic model lipid monolayers

The effect of a saponin-rich extract from rhizomes of Soapwort (Saponaria officinalis L) and four synthetic surfactants: sodium lauryl sulphate (SLS), sodium laureth sulphate (SLES), ammonium lauryl sulphate (ALS) and cocamidopropyl betaine (CAPB) on two model lipid monolayers is analyzed using surface pressure, surface dilatational rheology and fluorescence microscopy. The following monolayers were employed: dipalmitoylphosphatidylcholine/cholesterol mixture in a molar ratio of 7:3 (DPPC/CHOL) and Ceramide [AP]/stearic acid/cholesterol in a molar ratio of 14:14:10 (CER/SA/CHOL). They mimicked a general bilayer structure and an intercellular lipid mixture, respectively. Both lipid mixtures on Milli-Q water were first compressed to the initial surface pressure, Π₀ = 30 mN/m and then the subphase was exchanged with the respective (bio)surfactant solution at 1% (w/w). All four synthetic surfactants behaved in a similar way: they increased surface pressure to about 40 mN/m and reduced the storage modulus of surface dilational surface rheology, E′, to the values close to zero. The corresponding fluorescence microscopy pictures confirmed that the lipids mimicking the stratum corneum components were almost completely removed by the synthetic surfactants under the present experimental conditions. The components of the Soapwort extract (SAP) increased surface pressure to significantly higher values than the synthetic surfactants, but even more spectacular increase was observed for the storage modulus of the SAP-penetrated lipid monolayers (up to E′= 715 mN/m).     

Up-regulation of lipid metabolism and glycine betaine synthesis are associated with choline-induced salt tolerance in halophytic seashore paspalum

Choline may affect salt tolerance by regulating lipid and glycine betaine (GB) metabolism. This study was conducted to determine whether alteration of lipid profiles and GB metabolism may contribute to choline regulation and genotypic variations in salt tolerance in a halophytic grass, seashore paspalum (Paspalum vaginatum). Plants of Adalayd and Sea Isle 2000 were subjected to salt stress (200-mM NaCl) with or without foliar application of choline chloride (1 mM). Genotypic variations in salt tolerance and promotive effects of choline application on salt tolerance were associated with both the up-regulation of lipid metabolism and GB synthesis. The genotypic variations in salt tolerance associated with lipid metabolism were reflected by the differential accumulation of phosphatidylcholine and phosphatidylethanolamine between Adalayd and Sea Isle 2000. Choline-induced salt tolerance was associated with of the increase in digalactosyl diacylglycerol (DGDG) content including DGDG (36:4 and 36:6) in both cultivars of seashore paspalum and enhanced synthesis of phosphatidylinositol (34:2, 36:5, and 36:2) and phosphatidic acid (34:2, 34:1, and 36:5), as well as increases in the ratio of digalactosyl diacylglycerol: monogalactosyl diacylglycerol (DGDG:MGDG) in salt-tolerant Sea Isle 2000. Choline regulation of salt tolerance may be due to the alteration in lipid metabolism in this halophytic grass species.     

Biochemical responses to drought stress in mulberry (<Emphasis Type="Italic">Morus alba</Emphasis> L.): evaluation of proline,glycine betaine and abscisic acid accumulation in five cultivars

Five popularly grown mulberry cultivars (K-2, MR-2, TR-10, BC2-59 and S-13) were subjected to drought stress by withholding irrigation, to obtain leaf water potentials (Ψ_w) ranging from −0.75, −1.50 and −2.25 MPa. Accumulation of proline, glycine betaine and abscisic acid (ABA) were quantified in control and water stressed mulberry leaves. The activities of enzymes involved in proline accumulation including glutamate dehydrogenase (EC1.4.1.2-4), pyrroline-5-carboxylate synthetase (EC 1.2.1.41), pyrroline-5-carboxylate reductase (EC1.5.1.2), ornithine transaminase (EC 2.6.1.13) were significantly enhanced in the leaves of all the cultivars with decreasing leaf water potentials, while the activities of proline dehydrogenase (EC 1.5.1.2) were reduced with progressive increase in water stress. Accumulation of proline, glycine betaine and abscisic acid was relatively higher in S-13 and BC2-59 compared to K-2, MR-2 and TR-10 under water deficit conditions. Our results demonstrate that S-13 and BC2-59 have superior osmoprotectant mechanisms under water-limited growth regimes.     

Measurement of Free Choline in Plant Leaves by Capillary Electrophoresis

A low pH capillary electrophoresis (CE) was used for the measurement of free choline in plant leaves. Choline in the leaf extract was first converted to the benzoyl ester and put into CE. A well-resolved peak in the electropherogram was easily obtained. Involvement of enzymes in a two-step oxidation of choline to glycine betaine was evaluated in different plant species with the same mehod developed for glycine betaine and betaine aldehyde.     

Effects of Exogenous Proline and Glycinebetaine on the Salt Tolerance of Rice Cultivars

Glutathione reductase was purified from iron-grown Thiobacillus ferrooxidas AP19-3 to an electrophoretically homogeneous state. The enzyme had an apparent molecular weight of 100,000 and was composed of two identical subunits of molecular weight (M_rs, 52,000) as estimated by sodium dodecyl sulfate–polyacrylamide gel electrophoresis. A purified enzyme reduced one mole of the oxidized form of glutathione (GSSG) with one mole of NADPH to produce two moles of the reduced form of glutathione (GSH) and one mole of NADP⁺. The glutathione reductase was most active at pH 6.5 and 40°C, and had an isoelectric point at 5.1. The Michaelis constants of glutathione reductase for GSSG, NADPH, and NADH were 300, 26, and 125 μM, respectively.     

Betaine attenuates Alzheimer‐like pathological changes and memory deficits induced by homocysteine

Hyperhomocysteinemia (Hhcy) may induce memory deficits with β‐amyloid (Aβ) accumulation and tau hyperphosphorylation. Simultaneous supplement of folate and vitamin B12 partially restored the plasma homocysteine level and attenuated tau hyperphosphorylation, Aβ accumulation and memory impairments induced by Hhcy. However, folate and vitamin B12 treatment have no effects on Hhcy which has the methylenetetrahydrofolate reductase genotype mutation. In this study, we investigated the effects of simultaneous supplement of betaine on Alzheimer‐like pathological changes and memory deficits in hyperhomocysteinemic rats after a 2‐week induction by vena caudalis injection of homocysteine (Hcy). We found that supplementation of betaine could ameliorate the Hcy‐induced memory deficits, enhance long‐term potentiation (LTP) and increase dendritic branches numbers and the density of the dendritic spines, with up‐regulation of NR1, NR2A, synaptotagmin, synaptophysin, and phosphorylated synapsin I protein levels. Supplementation of betaine also attenuated the Hcy‐induced tau hyperphosphorylation at multiple AD‐related sites through activation protein phosphatase‐2A (PP2A) with decreased inhibitory demethylated PP2A_C at Leu309 and phosphorylated PP2A_C at Tyr307. In addition, supplementation of betaine also decreased Aβ production with decreased presenilin‐1 protein levels. Our data suggest that betaine could be a promising candidate for arresting Hcy‐induced AD‐like pathological changes and memory deficits.     

Structure of Porriolide,a New Metabolite from Alternaria porri

Compounds from a soil isolate of Penicillium sp. MG-11 showed remarkable convulsive activity against silkworms. Activity-based fractionation of an acetone extract of the fermentation products resulted in the isolation of four compounds. One was identified as verruculogen, which was an active principle. Another compound, acetoxydehydroaustin, was new and was structurally characterized by spectral data and a single-crystal X-ray analysis. The two other compounds were identified as dehydroaustin and austin on the basis of the spectral data. Although the latter three compounds were not active themselves, they enhanced the convulsive activity of verruculogen in a silkworm bioassay. Three additional compounds with no identifiable activity were also isolated. Two of them were identified as austinol and dehydroaustinol, and the third was determined to be a new related compound named neoaustin by an X-ray analysis of crystals.