Effects of Ultraviolet Radiation (UVA+UVB) and Copper on the Morphology,Ultrastructural Organization and Physiological Responses of the Red Alga Pterocladiella capillacea

The effect of ultraviolet (UV) radiation and copper (Cu) on apical segments of Pterocladiella capillacea was examined under two different conditions of radiation, PAR (control) and PAR+UVA+UVB (PAR+UVAB), and three copper concentrations, ranging from 0 (control) to 0.62, 1.25 and 2.50 μm . Algae were exposed in vitro to photosynthetically active radiation (PAR) at 70 μmol photons m^?2 s^?1, PAR + UVB at 0.35 W m^?2 and PAR +UVA at 0.70 W m^?2 during a 12‐h photocycle for 3 h each day for 7 days. The effects of radiation and copper on growth rates, content of photosynthetic pigments and photosynthetic performance were analyzed. In addition, samples were processed for light and transmission electron microscopy. The content of photosynthetic pigments decreased after exposure to radiation and Cu. Compared with PAR radiation and copper treatments modified the kinetics patterns of the photosynthesis/irradiance curve. The treatments also caused changes in the ultrastructure of cortical and subcortical cells, including increased cell wall thickness and accumulation of plastoglobuli, as well as changes in the organization of chloroplasts. The results indicate that the synergistic interaction between UV radiation and Cu in P. capillacea, led to the failure of protective mechanisms and causing more drastic changes and cellular imbalances.     

Supported bis(indenyl)– and bis(fluorenyl)–chromium catalysts for ethylene polymerization

Silica-supported bis(indenyl)– and bis(fluorenyl)–chromium catalysts show good activity in ethylene polymerization. For maximum productivity with the indenyl chromium catalyst, the silica must be dried, with higher dehydration temperatures giving a significant increase in polymerization activity. Less deactivation on thermal aging of the supported bis(indenyl)–chromium catalyst allows ethylene polymerization to proceed for many hours, which provides polyethylenes of low residual chromium content. In contrast to the behavior of supported chromocene catalysts, the indenyl–and fluorenyl–chromium catalysts require a higher hydrogen/ethylene ratio to achieve a specific polymer melt index. Nevertheless, highly saturated polyethylenes are produced with these new catalysts. This result indicates that chain transfer to hydrogen remains the major chain transfer reaction. Addition of cyclopentadiene to a supported indenyl–chromium catalyst provided a catalyst with a much higher transfer response to hydrogen. This result suggests that ligand exchange occurred, producing a supported chromocene catalyst. These overall results are consistent with an active-site model which comprises a supported divalent chromium center attached to an indenyl or fluorenyl ligand during the polymerization process. Polymerization is believed to occur by a coordinated anionic mechanism of the type previously discussed for a supported chromocene catalyst.     

Effects of Ultraviolet Radiation (UV‐A+UV‐B) on the Antioxidant Metabolism of the Red Macroalga Species Acanthophora spicifera (Rhodophyta,Ceramiales) From Different Salinity and Nutrient Conditions

Acanthophora spicifera (M.Vahl) Børgesen is a macroalga of great economic importance. This study evaluated the antioxidant responses of two algal populations of A. spicifera adapted to different abiotic conditions when exposed to ultraviolet‐A+ultraviolet‐B radiation (UV‐A+UV‐B). Experiments were performed using the water at two collection points for 7 days of acclimatization and 7 days of exposure to UVR (3 h per day), followed by metabolic analyses. At point 1, water of 30 ± 1 practical salinity unit (psu) had concentrations of 1.06 ± 0.27 mm ${\text{NH}}_4^{+}$, 8.47 ± 0.01 mm ${\text{NO}}_3^{?}$, 0.17 ± 0.01 mm ${\text{PO}}_4^{?3}$ and pH 7.88. At point 2, water of 35 ± 1 psu had concentrations of 1.13 ± 0.05 mm ${\text{NH}}_4^{+}$, 3.73 ± 0.01 mm ${\text{NO}}_3^{?}$, 0.52 ± 0.01 mm ${\text{PO}}_4^{?3}$ and pH 8.55. Chlorophyll a, phycobiliproteins, carotenoids, mycosporins, polyphenolics and antioxidant enzymes (catalase, superoxide dismutase and guaiacol peroxidase) were evaluated. The present study demonstrates that ultraviolet radiation triggers antioxidant activity in the A. spicifera. However, such activation resulted in greater responses in samples of the point 1, with lower salinity and highest concentration of nutrients.     

Expression of a Chitinase Gene from <Emphasis Type="Italic">Metarhizium anisopliae</Emphasis> in Tobacco Plants Confers Resistance against <Emphasis Type="Italic">Rhizoctonia solani</Emphasis>

The chit1 gene from the entomopathogenic fungus Metarhizium anisopliae, encoding the endochitinase CHIT42, was placed under the control of the CaMV 35S promoter, and the resulting construct was transferred to tobacco. Seventeen kanamycin-resistant transgenic lines were recovered, and the presence of the transgene was confirmed by polymerase chain reactions and Southern blot hybridization. The number of chit1 copies was determined to be varying from one to four. Copy number had observable effects neither on plant growth nor development. Substantial heterogeneity concerning production of the recombinant chitinase, and both general and specific chitinolytic activities were detected in leaf extracts from primary transformants. The highest chitinase activities were found in plants harboring two copies of chit1 inserts at different loci. Progeny derived from self-pollination of the primary transgenics revealed a stable inheritance pattern, with transgene segregation following a mendelian dihybrid ratio. Two selected plants expressing high levels of CHIT42 were consistently resistant to the soilborne pathogen Rhizoctonia solani, suggesting a direct relationship between enzyme activity and reduction of foliar area affected by fungal lesions. To date, this is the first report of resistance to fungal attack in plants mediated by a recombinant chitinase from an entomopathogenic and acaricide fungus.     

Effects of Ultraviolet Radiation (UVA+UVB) on Young Gametophytes of Gelidium floridanum: Growth Rate,Photosynthetic Pigments,Carotenoids, Photosynthetic Performance,and Ultrastructure

This study investigated the effects of radiation (PAR+UVA+UVB) on the development and growth rates (GRs) of young gametophytes of Gelidium floridanum. In addition, photosynthetic pigments were quantified, carotenoids identified, and photosynthetic performance assessed. Over a period of 3 days, young gametophytes were cultivated under laboratory conditions and exposed to photosynthetically active radiation (PAR) at 80 μmol photons m^?2 s^?1 and PAR+UVA (0.70 W m^?2)+UVB (0.35 W m^?2) for 3 h per day. The samples were processed for light and electron microscopy to analyze the ultrastructure features, as well as carry out metabolic studies of GRs, quantify the content of photosynthetic pigments, identify carotenoids and assess photosynthetic performance. PAR+UVA+UVB promoted increase in cell wall thickness, accumulation of floridean starch grains in the cytoplasm and disruption of chloroplast internal organization. Algae exposed to PAR+UVA+UVB also showed a reduction in GR of 97%. Photosynthetic pigments, in particular, phycoerythrin and allophycocyanin contents, decreased significantly from UV radiation exposure. This result agrees with the decrease in photosynthetic performance observed after exposure to ultraviolet radiation, as measured by a decrease in the electron transport rate (ETR), where values of ETRmax declined approximately 44.71%. It can be concluded that radiation is a factor that affects the young gametophytes of G. floridanum at this stage of development.     

Astaxanthinogenesis in the yeastPhaffia rhodozyma

Astaxanthin is a diketo-dihydroxy-carotenoid produced byPhaffia rhodozyma, a basidiomicetous yeast. A low-cost fermentation medium consisting of raw sugarcane juice and urea was developed to exploit the active sucrolytic/urelolytic enzyme apparatus inherent to the yeast. As compared to the beneficial effect of 0.1 g% urea, a ready nitrogen source, mild phosphoric pre inversion of juice sucrose to glucose and fructose, promptly fermentable carbon sources, resulted in smaller benefits. Corn steep liquor (CSL) was found to be a valuable supplement for both yeast biomass yield (9.2 g dry cells/L) and astaxanthin production (1.3 mg/g cells). Distillery effluent (vinace), despite only a slightly positive effect on yeast growth, allowed for the highest pigment productivity (1.9 mg/g cells). Trace amounts of Ni² (1 mg/L, as a cofactor for urease) resulted in controversial effects, namely, biomass decrease and astaxanthin increase, with no effect on the release (and uptake) of ammonium ion from urea. Since the synthesized astaxanthin is associated with the yeast cell and the pigment requires facilitated release for aquaculture uses (farmed fish meat staining), an investigation of the yeast cell wall was undertaken using detergent-treated cells. The composition of the rigid yeast envelope was found to be heterogeneous. Its partial acid or enzymatic depolymerization revealed glucose and xylose as common monomeric units of the cell-wall glycopolymers. Yeast cell-wall partial depolymerization with appropriate hydrolases may improve the pigment bioavailability for captive aquatic species and poultry.

     

Photoacclimation Responses of the Brown Macroalga Sargassum Cymosum to the Combined Influence of UV Radiation and Salinity: Cytochemical and Ultrastructural Organization and Photosynthetic Performance

The photoacclimation responses of the brown macroalga Sargassum cymosum were studied to determine its cytochemical and ultrastructural organization, as well as photosynthetic pigments and performance. S. cymosum was cultivated in three salinities (30, 35 and 40 psu) under four irradiation treatments: PAR‐only, PAR + UVA, PAR + UVB and PAR + UVA + UVB. Plants were exposed to PAR at 70 μmol photons m^?2 s^?1, PAR + UVB at 0.35 W m^?2 and PAR +UVA at 0.70 W m^?2 for 3 h per day during 7 days in vitro. Growth rate was not significantly affected by any type of radiation or salinity. The amount of pigments in S. cymosum was significantly influenced by the interaction of salinity and radiation treatments. Compared with PAR‐only, UVR treatments modified the kinetics patterns of the photosynthesis/irradiance curve. After exposure to UVR, S. cymosum increased cell wall thickness and the presence of phenolic compounds. The number of mitochondria increased, whereas the number of chloroplasts showed few changes. Although S. cymosum showed insensitivity to changes in salinity, it can be concluded that samples treated under four irradiation regimes showed structural changes, which were more evident, but not severe, under PAR + UVB treatment.     

Effects of UVB radiation on the agarophyte Gracilaria domingensis (Rhodophyta,Gracilariales): Changes in cell organization,growth and photosynthetic performance

The effects of ultraviolet radiation-B (UVBR) in apical segments of the red macroalgae Gracilaria domingensis (Kützing) Sonder ex Dickie were examined in vitro. Over a period of 21 days, the segments were cultivated and exposed to photosynthetically active radiation (PAR) at 80 μmol photons m^?2 s^?1 and PAR + UVBR at 1.6 W m^?2 for 3 h per day. The samples were processed for electron microscopy, as well as histochemical analysis, and growth rate, photosynthetic pigment contents and photosynthetic performance were measured. Toluidine Blue reaction showed metachromatic granulations in vacuole and lenticular thickness, while Coomassie Brilliant Blue showed a higher concentration of cytoplasmic organelles, and Periodic Acid Schiff stain showed an increase in the number of floridean starch grains. UVBR also caused changes in the ultrastructure of cortical and subcortical cells, which included an increased number of plastoglobuli, changes in mitochondrial organization, destruction of chloroplast internal organization, and the disappearance of phycobilisomes. The algae cultivated under PAR-only showed growth rates of 6.0% day^?1, while algae exposed to PAR + UVBR grew only 2.8% day^?1. Compared with algae cultivated with PAR-only, the contents of photosynthetic pigments, including chlorophyll a, phycoerythrin, phycocyanin and allophycocyanin, decreased after exposure to PAR + UVBR, and significant differences were observed. Finally, analysis of these four photosynthetic parameters also showed reduction after exposure to PAR + UVBR: maximum photosynthetic rate, photosynthetic efficiency, photoinhibition and relative electron transport rate. Taken together, these findings strongly suggested that UVBR negatively affects the agarophyte G. domingensis.     

Acetobacter cellulosic biofilms search for new modulators of cellulogenesis and native membrane treatments

Since natural substances like pseudoxanthins exert a positive effect on the cellulogenic ability ofAcetobacter xylinum when producing cellulosic pellicles suitable for skin burn therapy, new defined and complex modulators were sought. Ca²⁺ and Mg²⁺ (4 mM) were strongly stimulatory. Na⁺ had no effect and K⁺ was inhibitory. Ammonium dihydrogen phosphate (0.12 g/L) ensured the same nitrogen supply as the same concentration of yeast extract as measured by cellomembrane dry wt./yield albeit higher yeast extract supplies produced thicker membranes. Corn steep liquor (CSL) was also progressively beneficial from 0.125 to 0.5 mL/L, and this yield could be further improved by the combination of CSL with a tea infusion (source of caffeine). Uridine (precursor for UDP-Glc, sugar donor in cellulose biosynthesis), guanine, guanosine, and its butirylated derivatives (precursors for the positive modulator of cellulose synthetase, di-cGMP) resulted in only moderate stimulation. Sodium phytate and betaine were also slightly stimulatory. The fibrilar product from a newAcetobacter isolate (Ax-M) was characterized as cellulose by comparison with the solid-state¹³C-NMR of algal cellulose. Its X-ray diffractogram was a confirmatory analysis. After incorporation of tamarind xyloglucan to previously air-dried cellulosic pellicles, diffractometry displayed only slight differences. Mercerized (5M NaOH) fresh cellulosic biofilms underwent drastic size reduction (3.5-fold), turning compact nut still flexible if maintained wet.