Influence of ultraviolet-C on the compositions of cell-wall polysaccharides and carbohydrase activities of Silene vulgaris callus

UV-C irradiation (254 nm) was found to enhance the secretion of some cell-wall-degrading enzymes, especially the following carbohydrases: beta-galactosidase, alpha-L-arabinofuranosidase, polygalacturonase, pectinesterase, cellulase, xylanase, and beta-xylosidase, in the campion callus, contributing thereby to an alteration in the polysaccharide structure. The relative amounts of the galactose and arabinose residues in pectin (silenan) and of arabinose in arabinogalactan of calli irradiated during the exponential phase were shown to decrease during the stationary phase. A decrease in the degree of SV methylesterification was found for the irradiated callus. These alterations were found to persist over a long period of culturing time. Decreasing the relative amounts of the arabinose residues in arabinogalactan and pectin and the galactose residues in silenan corresponded to increasing activity of alpha-L-arabinofuranosidase and beta-galactosidase, respectively, due to treatment with UV-C. UV-C irradiation may be used as a tool for modifying the structural features of the cell-wall polysaccharides, such as the relative amounts of galactose and arabinose residues in the side chains of polysaccharides, with the purpose of obtaining physiologically active polysaccharides with the desired properties and structural features.     

Ultraviolet Rays Promote Development of Photosystem II Photochemical Activity and Accumulation of Phenolic Compounds in the Tea Callus Culture (<Emphasis Type="Italic">Camellia sinensis</Emphasis>)

Effect of UV-B rays (280–320 nm) on photosynthetic electron transport and production of phenolic compounds in tea (Camellia sinensis L.) callus culture grown in white light was investigated. When white light was supplemented with UV radiation, the culture growth was retarded and morphological characteristics were modified. These conditions promoted the formation of chlorophyll-bearing cells and altered the ability of cultured cells to accumulate phenolic compounds, including flavans specific to Camellia sinensis. By the end of the culturing cycle (on the 45th day), the total content of phenolic compounds in the culture grown under supplementary UV irradiation was almost 1.5 times higher than in the control culture. The UV rays greatly stimulated photosystem II (PSII) activity in phototrophic cells of the callus culture, which was indicated by a large increase in the ratio of variable chlorophyll fluorescence to maximal fluorescence. This ratio was as low as 0.19 in cells cultured in white light and increased to 0.53 in the cell culture grown under white and UV light. The kinetics of dark relaxation of chlorophyll variable fluorescence, related to reoxidation of PSII primary acceptor, contained either two or three components, depending on the absence or presence of UV radiation, respectively. An artificial electron acceptor of PSI, methyl viologen modified the kinetics of dark decay of chlorophyll variable fluorescence in a characteristic manner, implying that photosynthetic electron transport was mediated by PSI and PSII in both treatments (culturing in white light with and without UV-B). It is concluded that stimulatory effect of UV rays on the parameters examined in phototrophic regions of Camellia tissue culture is determined by photoexcitation of a regulatory pigment that absorbs quanta in blue and long-wave UV spectral regions.     

Effect of calcium, phosphate and nitrogen on cell growth and biosynthesis of cell wall polysaccharides by Silene vulgaris cell culture

Medium nutrients such as calcium, phosphorus, nitrogen and nitrate to ammonium ratio have significant influence on the growth, biosynthetic and biochemical characteristics of polysaccharides produced by Silene vulgaris (M.) G. cell culture. Cell growth and production of polysaccharides was limited by an absence of any of these components in the medium. Optimal growth of the callus and production of arabinogalactan were achieved at 1.5-4.5 microM calcium while the optimal production of pectin named silenan was observed at 3.0-4.5 microM. The phosphate contents in the medium in the range of 0.63-3.75 microM were favorable for callus growth. Production of silenan was maximal at 1.25-3.75 microM phosphate. Optimal growth of the callus was achieved at 30-90 microM nitrogen. Maximal production of silenan was observed at 60 microM nitrogen while the optimal production of arabinogalactan was at 90 microM nitrogen (at ratio of NH(4)(+):NO(3)(-) as 1:2). A presence both of nitrate and ammonium is needed for the silenan biosynthesis (the NH(4)(+):NO(3)(-) ratio as 1:1 and 1:2). Yields and volumetric production of arabinogalactan were maximal at deletion of ammonium from the nutrient medium (ratio 0:1). Absence of calcium or nitrogen in the medium leads to a decrease of the galacturonic acid residues in silenan. The galactose residues contents in arabinogalactan were decreased in the absence of nitrogen and calcium in the medium.     

Effect of Ultraviolet (UV-B) Radiation on the Formation and Localization of Phenolic Compounds in Tea Plant Callus Cultures

The effect of ultraviolet (UV-B) radiation on the accumulation and tissue localization of phenolic compounds in two strains of callus cultures of tea plant (Camellia sinensisL.) were investigated. The strains differed in their morphological and physiological characteristics and biosynthetic capacity. UV-B radiation hampered culture growth, decreased the size of callus-forming cells and promoted the accumulation of soluble and, to a lesser extent, polymeric forms of phenolic compounds, such as lignin. This accumulation was accompanied by an increase in the phenolic compound deposition in cell walls and intercellular space and by deposition of a lignin-like material on the surface of callus cultures. The strain characterized by an increased formation of phenolic compounds was more resistant to UV-B radiation as compared to that with lower phenolic productivity.     

施硅提高水稻叶片对紫外线胁迫的抗性

采用加硅与缺硅营养液培养的方法, 首次研究证明硅能提高水稻(Oryza sativa L.)叶片抗紫外线胁迫的能力。结果表明, 在紫外胁迫条件下,缺硅水稻叶片表面出现明显的棕色伤害斑点,而加硅叶片未出现伤害症状。硅在水稻表皮细胞壁及细胞内部的积累明显促进了紫外吸收物质在表皮细胞中的聚集,使表皮中可溶性酚类物质含量提高17%,不溶性紫外吸收物质的含量增加65%左右。荧光显微镜观察表明,在表皮细胞外壁或胞内沉积的水合二氧化硅固体中包含着大量不溶性的酚类化合物,它们与可溶性酚类物质一起在叶片的上、下表皮细胞中形成了吸收紫外线的屏障。     

An alternate carbon source for enhancing production of polysaccharides by Silene vulgaris callus

Pectin termed silenan and acidic arabinogalactan were isolated as cell-wall polysaccharides of Silene vulgaris callus in the presence of various carbon sources as components of the media. The maximum yields, productivity per litre of medium and production per day of acidic arabinogalactan, were achieved using glucose or galactose as the carbon source. Sucrose was found to increase the production of the polysaccharides. Yields, productivity and rate of production of arabinogalactan per day were decreased in the presence of arabinose. Yields of silenan, productivity and rate of production per day were closely related irrespective of the sugar used as the carbon source in the media (sucrose, glucose or galactose) and yields of silenan from the callus growing on arabinose were comparable. A concentration of sucrose in the 20-50 g/L range enhanced the biosynthesis of silenan and at 50 g/L the silenan contained the linear backbone and the ramified regions of the macromolecule.     

施硅提高水稻叶片对紫外线胁迫的抗性

采用加硅与缺硅营养液培养的方法,首次研究证明硅能提高水稻(Oryza sativa L.)叶片抗紫外线胁迫的能力.结果表明,在紫外胁迫条件下,缺硅水稻叶片表面出现明显的棕色伤害斑点,而加硅叶片未出现伤害症状.硅在水稻表皮细胞壁及细胞内部的积累明显促进了紫外吸收物质在表皮细胞中的聚集,使表皮中可溶性酚类物质含量提高17%,不溶性紫外吸收物质的含量增加65%左右.荧光显微镜观察表明,在表皮细胞外壁或胞内沉积的水合二氧化硅固体中包含着大量不溶性的酚类化合物,它们与可溶性酚类物质一起在叶片的上、下表皮细胞中形成了吸收紫外线的屏障.     

Influence of the fungus Trichoderma harzianum on the enzyme and polysaccharide composition of Silene vulgaris callus

Activities of polygalacturonase and 1,3-β-glucanase increased in campion (Silene vulgaris) callus cells during co-cultivation with the fungus Trichoderma harzianum. This was associated with a decrease in galacturonic acid residues in the pectic polysaccharide of campion silenan and also in the production of pectin by the callus. Co-cultivation of the callus and the fungus resulted in an increase in contents of arabinose residues in the intracellular arabinogalactan and in contents of galactose residues in the extracellular arabinogalactan.     

Pectin substances of the callus culture of <Emphasis Type="Italic">Silene vulgaris</Emphasis> (M.) G.

Pectin-protein fraction SVC was isolated from the callus culture of the bladder campion (Silene vulgaris). The main components in it were residues of D-galacturonic acid, galactose, arabinose, rhamnose, and protein. Using ion-exchange chromatography, ultrafiltration, and acid and enzymatic hydrolysis, it was shown that SVC contained a mixture of molecules of linear pectin, branched pectin polysaccharide, and pectin-protein polymer. A fragment of the linear chain of galacturonan amounted to more than half of the entire carbohydrate silenan chain. The branched area of the macromolecule is represented by rhamnogalacturonan I. The pectin-protein polymer consisted mainly of protein and weakly branched pectin fragments with molecular mass of more than 300 kDa.     

Influence of UV-B radiation on bacterial activity in coastal waters

The impact of UV-B radiation (290–315 nm) on bacterialactivity and abundance in coastal water was studied in mesocosmexperiments in May 1994 and May 1995 at Kristineberg MarineResearch Station, Sweden. Mesocosms (6 m³) containing naturalpelagic communities were exposed either to ambient irradiation(AMB), ambient irradiation with enhanced UV-B (+UV) (0.7 W m^–24 h every day around noon), or ambient irradiation screenedfor UV-B (–UV). Bacterial activity in the mesocosms wasmeasured by means of thymidine incorporation in short-term testsduring incubations at ambient irradiation, at ambient irradiationwith enhanced UV-B, and at ambient irradiation screened forUV-B. In +UV mesocosms, bacterial activity was significantlystimulated when incubated at ambient radiation. The stimulatingeffect was suggested to be due to an increase in carbon or nutrientsupply through a photodegradation of recalcitrant dissolvedorganic material (DOM). Low attenuation coefficients for UV-Band PAR (400–700 nm) in the +UV mesocosms supported thishypothesis. The bacterial activity in +UV mesocosms, however,was inhibited when incubations were made at enhanced UV-B irradiation,implying that the bacteria had become more sensitive to UV-Bradiation. The increased sensitivity to UV-B exposure in bacterialassemblages that already had been exposed and stressed by UV-Bradiation is suggested to be due to an overburdening of theenergy-consuming DNA repair mechanism. The data suggest thatincreased UV-B radiation, which might occur with ozone depletion,may both stimulate and suppress bacterial activity in coastalwaters, implying that the net outcome of enhanced UV-B radiationcould be an unchanged bacterial activity.     

Pectin substances of the callus culture of Silene vulgaris (M.) G

Pectin-protein fraction SVC was isolated from the callus culture of the bladder campion (Silene vulgaris). The main components in it were residues of D-galacturonic acid, galactose, arabinose, rhamnose, and protein. Using ion-exchange chromatography, ultrafiltration, and acid and enzymatic hydrolysis, it was shown that SVC contained a mixture of molecules of linear pectin, branched pectin polysaccharide, and pectin-protein polymer. A fragment of the linear chain of galacturonan amounted to more than half of the entire carbohydrate silenan chain. The branched area of the macromolecule is represented by rhamnogalacturonan I. The pectin-protein polymer consisted mainly of protein and weakly branched pectin fragments with molecular mass of more than 300 kDa.     

Quantitative changes in secondary metabolites of dark-leaved willow (Salix myrsinifolia) exposed to enhanced ultraviolet-B radiation

This is a study of the impact of increased ultraviolet-B (UV-B) radiation on the secondary chemistry of Salix myrsinifolia (dark-leaved willow). For nearly two decades, the loss of stratospheric ozone above the high latitudes of the Northern Hemisphere has increased UV-B radiation (280–320 nm) over the long-term mean. Willows (Salicaceae) are widely distributed in these northern regions. To determine the effects of increased UV-B radiation on willows, the plantlets of three clones of S. myrsinifolia were grown under ambient (3.6 kJ m⁻² day⁻¹) or enhanced (7.18 kJ m⁻² day⁻¹) UV-B irradiance. After the 2-week indoor experiment, the concentrations of UV-B-screening phenolics (flavonoids and phenolic acids) and low-UV-B-screening phenolics (salicylates and condensed tannins) in fresh leaves were investigated and the biomass of leaves, stems and roots was determined. As expected, the total amount of flavonoids in willow leaves clearly increased when plantlets were exposed to higher UV-B irradiation. However, the degree of increase of individual compounds varied: luteolin-7-glucoside, monomethyl-monocoumaryl-luteolin-7-glucoside and one myricetin derivative increased significantly, while the apigenin-7-glucuronide increased only slightly. The enhanced UV-B also increased the amount of p -hydroxycinnamic acid derivative. The UV-B effects on other phenolic acids and tannins were minor. In contrast to the other phenolics, the amounts of two salicylates, salicin and saligenin, decreased under enhanced UV-B irradiation. Our results indicate that the concentrations of both UV-B-screening and low-UV-B-screening phenolic compounds in leaves of S. myrsinifolia may vary in response to elevated UV-B radiation. However, while the UV-B protective flavonoids and phenolic acids accumulate during UV-B exposure, the concentrations of certain salicylates decrease.     

The effect of ultraviolet radiation on the growth and polysaccharide composition of a callus culture of Silene vulgaris

Ultraviolet radiation (wavelength, 280-315 nm; power, 0.2-13.0 W/m2; exposure, 1 or 3 h) was shown to change the growth of campion callus and the polysaccharide (pectin and arabinogalactan) composition of cell walls. An increase in the concentration of polysaccharides and a decrease in the content of arabinose and galactose residues in pectin and arabinogalactan were noted. For the majority of calluses, growth indices, specific growth rate, and biomass productivity (per 11 medium) were almost the same as in nonirradiated control cells. Maximum values of the growth index and specific growth rate, determined for dry biomass, were observed at a low dose of irradiation (0.2 W/m2) and an exposure of 3 h. A considerable decrease in the content of arabinose and galactose in pectin was noted at high doses of irradiation (exposure, 3 h). Samples of arabinogalactan were characterized by variable arabinose to galactose ratios, which were in the range 1 : (3.4-8.3).     

UV-B-induced synthesis of photoprotective pigments and extracellular polysaccharides in the terrestrial cyanobacterium Nostoc commune.

Liquid cultures of the terrestrial cyanobacterium Nostoc commune derived from field material were treated with artificial UV-B and UV-A irradiation. We studied the induction of various pigments which are though to provide protection against damaging UV-B irradiation. First, UV-B irradiation induced an increase in carotenoids, especially echinenone and myxoxanthophyll, but did not influence production of chlorophyll a. Second, an increase of an extracellular, water-soluble UV-A/B-absorbing mycosporine occurred, which was associated with extracellular glycan synthesis. Finally, synthesis of scytonemin, a lipid-soluble, extracellular pigment known to function as a UV-A sunscreen, was observed. After long-time exposure, the UV-B effect on carotenoid and scytonemin synthesis ceased whereas the mycosporine content remained constantly high. The UV-B sunscreen mycosporine is exclusively induced by UV-B (< 315 nm). The UV-A sunscreen scytonemin is induced only slightly by UV-B (< 315 nm), very strongly by near UV-A (350 to 400 nm), and not at all by far UV-A (320 to 350 nm). These results may indicate that the syntheses of these UV sunscreens are triggered by different UV photoreceptors.     

The effect of ultraviolet radiation on the growth and polysaccharide composition of a callus culture of Silene vulgaris

Ultraviolet radiation (wavelength, 280–315 nm; power, 0.2–13.0 W/m²; exposure, 1 or 3 h) was shown to change the growth of campion callus and the polysaccharide (pectin and arabinogalactan) composition of cell walls. An increase in the concentration of polysaccharides and a decrease in the content of arabinose and galactose residues in pectin and arabinogalactan were noted. For the majority of calluses, growth indices, specific growth rate, and biomass productivity (per 11 medium) were almost the same as in nonirradiated control cells. Maximum values of the growth index and specific growth rate, determined for dry biomass, were observed at a low dose of irradiation (0.2 W/m²) and an exposure of 3 h. A considerable decrease in the content of arabinose and galactose in pectin was noted at high doses of irradiation (exposure, 3 h). Samples of arabinogalactan were characterized by variable arabinose to galactose ratios, which were in the range 1: (3.4–8.3).     

Fungal melanin inhibitor and related compounds from Penicillium decumbens

In Silene vulgaris (M.) G. cell culture three growth phases were distinguished, namely, a lag phase, an exponential phase and a stationary phase. Pectin termed silenan and an acidic arabinogalactan were isolated as cell wall polysaccharides of S. vulgaris callus at the different growth phases during culture. Production of silenan as the galacturonan (or rhamnogalacturonan) core was observed at the beginning of the exponential phase and at the stationary phase of the callus growth. Arabinogalactan, containing the galacturonic acid residues, is formed at the exponential phase followed by attachment to the core of silenan in the middle of the exponential phase. The arabinogalactan constituent of silenan appeared to be destroyed gradually at the stationary growth phase. The monosaccharide compositions of silenan and arabinogalactan were determined at various phases of the callus growth. Silenan was found to be formed in maximum amounts at the exponential phase of the cell growth. Insignificant alterations of the yields of acidic arabinogalactan were found during culture while total productivity per litre of medium and rate of production per day of arabinogalactan were found to be maximal at the exponential phase of growth.     

Production of polysaccharides by Silene vulgaris callus culture depending on carbohydrates of the medium

Sources of carbohydrate nutrition such as sucrose, glucose, and galactose, with the exception of arabinose, were shown to influence positively callus growth and polysaccharide (pectin silenan and acidic arabinogalactan) biosynthesis. Galactose was found to cause a stimulatory effect on yield and productivity of arabinogalactan. Low concentrations of sucrose failed to support the cell growth and polysaccharide biosynthesis. Increasing sucrose concentrations led to biomass accumulation but failed to enhance efficiency of the substrate utilization. The optimal medium for the campion cell culture growth was found to be one containing 30 g/liter of sucrose or a mixture of sucrose with glucose (in 15 g/liter). Increasing sucrose concentrations in the medium from 30 to 100 g/liter failed to significantly influence the polysaccharide yields while the polysaccharide productivity per liter of the medium grew due to promotion of culture productivity in biomass. Variations of the carbon sources in the nutrient media were shown to influence insignificantly the biochemical characteristics of arabinogalactan and silenan while an increase in the sucrose concentration to 50-100 g/liter led to a diminution of the galacturonic acid content in silenan and to changes in contents of the neutral monosaccharide residues in silenan and arabinogalactan.     

The effect of UV-B and UV-C radiation on Hibiscus leaves determined by ultraweak luminescence and fluorescence induction

The effects of UV-C (254 nm) and UV-B (280-320 nm) on chlorophyll fluorescence induction and ultraweak luminescence (UL) in detached leaves of Hibiscus rosa-sinensis L. were investigated. UL from leaves exposed to UV-B and UV-C radiation reached a maximum 72 h after irradiation. In both cases most of the light was of a wavelength over 600 nm. An increase in the percentage of long wavelength light with time was detected. UV radiation increased peroxidase activity, which also reached a maximum 72 h after irradiation. UV-B and UV-C both reduced variable chlorophyll fluorescence. No effect on the amount of chlorophyll or UV screening pigments was observed with the short-term irradiation used in this investigation.     

Structural studies of arabinogalactan and pectin from Silene vulgaris (M.) G. callus

Arabinogalactan and pectin (named silenan) were isolated from Silene vulgaris (M.) G. callus. Fractionation by ion-exchange chromatography on DEAE-cellulose and digestion with pectinase demonstrated that silenan from S. vulgaris callus (80% of D-galacturonic acid) and silenan from the aerial part of the campion S. vulgaris are similar: both pectins contain a high quantity of homogalacturonan segments. The NMR spectral data and mass spectrometry of the purified polysaccharide and its fragment obtained by Smith degradation confirmed that the core of the arabinogalactan consisted of the different segments of β-1,3-D-galactopyranan. Some of the β-galactopyranose residues of the backbone are branched at O-6. The side chains of the arabinogalactan were shown to contain residues of terminal and 3-O-substituted β-galactopyranose, terminal α-arabinofuranose and α-rhamnopyranose, and 2-O-substituted α-rhamnopyranose. The α-rhamnopyranose residues in the sugar chain appeared to be 2-O-glycosylated by the β-1,4-D-galactopyranosyl uronic acid residues. Published in Russian in Biokhimiya, 2006, Vol. 71, No. 6, pp. 798–807.     

Responses of a rice-field cyanobacterium Anabaena siamensis TISTR-8012 upon exposure to PAR and UV radiation

The effects of PAR and UV radiation and subsequent responses of certain antioxidant enzymatic and non-enzymatic defense systems were studied in a rice field cyanobacterium Anabaena siamensis TISTR 8012. UV radiation resulted in a decline in growth accompanied by a decrease in chlorophyll a and photosynthetic efficiency. Exposure of cells to UV radiation significantly affected the differentiation of vegetative cells into heterocysts or akinetes. UV-B radiation caused the fragmentation of the cyanobacterial filaments conceivably due to the observed oxidative stress. A significant increase of reactive oxygen species in vivo and DNA strand breaks were observed in UV-B exposed cells followed by those under UV-A and PAR radiation, respectively. The UV-induced oxidative damage was alleviated due to an induction of antioxidant enzymatic/non-enzymatic defense systems. In response to UV irradiation, the studied cyanobacterium exhibited a significant increase in antioxidative enzyme activities of superoxide dismutase, catalase and peroxidase. Moreover, the cyanobacterium also synthesized some UV-absorbing/screening substances. HPLC coupled with a PDA detector revealed the presence of three compounds with UV-absorption maxima at 326, 331 and 345 nm. The induction of the biosynthesis of these UV-absorbing compounds was found under both PAR and UV radiation, thus suggesting their possible function as an active photoprotectant.