Copper exposure reduces production of red carotenoids in a marine copepod

Sub-lethal exposure to copper has been shown to modulate both mitochondrial function and antioxidant gene expression in zooplankton. To date, however, researchers have not identified a quantifiable phenotypic trait that reliably indicates such physiological responses to copper exposure. Red ketocarotenoids are abundant in marine zooplankton serving both physiological and coloration roles, and their production is sensitive to environmental stress. In this study the expression of mitochondrial gene cytochrome c oxidase I (COI) and antioxidant gene glutathione reductase (GR), and the production of red ketocarotenoid, astaxanthin, was measured in response to sub-lethal copper exposure. We found that mRNA of COI and GR was more abundant in copper-exposed copepods than controls, suggesting there was a physiological response to copper exposure. At the same time, copper-exposed copepods produced less astaxanthin than controls. We suggest that ketocarotenoid content of zooplankton has the potential to be a sensitive bioindicator of marine environmental pollution. Understanding how cellular responses to environmental stressors manifest in the phenotypes of marine animals will greatly increase our capacity to monitor marine ecosystem health.     

Lipid and pigment changes during shoot initiation in cultured explants of Pinus radiata

Cotyledon explants of radiata pine contain principally lipid and protein reserve materials, which decline during shoot initiation. This process was followed phytochemically and ultrastructurally. Fatty acid and sterol analyses indicated that there were both quantitative and qualitative changes in the different classes of lipid. The most pronounced changes were an increase in the linolenic acid content of the polar lipids and the appearance of stigmasterol during shoot initiation. There was also a continued increase in chlorophyll and carotenoid levels, which paralleled chloroplast development. It appears that the changes observed were similar to those that occur in cotyledons during normal seedling development.     

Hydrophilic carotenoids: facile syntheses of carotenoid oxime hydrochlorides as long-chain, highly unsaturated cationic (bola)amphiphiles

Stable cationic carotenoid aggregates — predominantly of the J-type — develop when the hydrochlorides of carotenoid aldoximes and ketoximes are exposed to water. The oxime hydrochlorides are obtained by simple syntheses from commercially available food color carotenoids. Bluish-purple, unstable transient compounds were observed during hydrochlorination performed at liquid nitrogen temperature.     

Photo-oxidative damage in the ripening tomato fruit: Protective role of superoxide dismutase

Factors relating to photo-oxidative damage in tomatoes were investigated during maturation of the fruit and upon induction of sunscald. Superoxide dismutase (SOD) activity passed through a minimum at the mature-green and breaker stages of ripening and availability of zinc and copper did not appear to be a limiting factor in the synthesis of the enzyme. Iron levels were maximal and total carotenoid concentrations were lowest during the same mature-green and breaker stages of maturation, while chlorophyll was starting to decrease but was still present in large amounts. Peroxidase activity decreased steadily during ripening. Artificial induction of tolerance to photodynamic damage by controlled heat treatment was accompanied by an increase in SOD activity, while carotenoid levels and peroxidase activity did not change. These findings support the thesis that the previously reported susceptibility of tomatoes to photodynamic damage, i.e. sunscald, during the mature-green and breaker stages of maturation is related to enhanced formation of superoxide ions, at a time when chloroplast structure begins to break down. SOD, by scavenging the superoxide, appears to supplement the protective action of carotenoids against photo-oxidative injury.     

Relationship between growth irradiance and the xanthophyll cycle pool in the diatom Nitzschia palea

The size and de-epoxidation state of the xanthophyll cycle pool was measured in cultures of Nitzschia palea grown at six fluence rates in continuous light or with a 12 h photoperiod. In both series the size of the pool increased with increasing irradiance. The de-epoxidized form, diatoxanthin, was only present at fluence rates saturating for growth. The portion of diadinoxanthin, which was not readily de-epoxidized in saturating light, was constant and not related to the size of the pool. In the culture grown in a light-dark cycle at 300 μmol photons m^-2 s^-1 (PAR) increasing de-epoxidation took place in the latter half of the photoperiod, when the rate of photosynthesis was decreasing. A rapid, spectrophotometric method for measuring the extent of de-epoxidation of the xanthophyll cycle pool in a culture of diatoms is described. Upon addition of a small volume of hydrochloric acid to an extract of pigments in 90% acetone, the absorbance at 480 nm is reduced. The size of the reduction is a measure of the state of the xanthophyll cycle pool, since the absorbance of diatoxanthin is reduced by 5%, but the absorbance of diadinoxanthin by 87% due to an epoxide-furanoid rearrangement, which causes the absorption spectrum to be shifted by ca 20 nm towards shorter wavelengths.     

Effect of visible light on carotenogenesis in arthroconidiating Trichophyton mentagrophytes

The effect of visible light on carotenoid content in the dermatophyte Trichophyton mentagrophytes ATCC 26323 was investigated. The fungus T. mentagrophytes accumulated several carotenoids when arthroconidiated on Sabouraud glucose agar at 37°C. When this fungus was irradiated with moderate fluence rates of white light, the resultant arthroconidia contained considerably less carotenoids in comparison with dark controls although growth and arthroconidiation of this fungus were not at all affected by visible light. The reduction of carotenoid content in arthroconidia was due primarily to blue light, although red light caused a slight decrease in pigmentation. The suppressive effect of visible light on pigmentation was fluence rate dependent. Carotenoid accumulation in arthroconidia was inversely and exponentially related to the fluence rate of light. Carotenoid formation in arthroconidiating T. mentagrophytes was neither photoinducible nor photostimulative. An analysis of isolated carotenoids revealed that visible light caused a quantitative reduction in pigmentation, and no single carotenoid was selectively decreased.Non-standard abbreviations PI pigmentation index - r coefficient of correlation     

Variations in carotenoid content and acyl chain composition in exponential,stationary and biofilm states of Staphylococcus aureus,and their influence on membrane biophysical properties

Bacteria are often found in close association with surfaces, resulting in the formation of biofilms. In Staphylococcus aureus (S. aureus), biofilms are implicated in the resilience of chronic infections, presenting a serious clinical problem world-wide. Here, S. aureus biofilms are grown under flow within clinical catheters at 37 °C. The lipid composition and biophysical properties of lipid extracts from these biofilms are compared with those from exponential growth and stationary phase cells. Biofilms show a reduction in iso and anteiso branching compensated by an increase in saturated fatty acids compared to stationary phase. A drastic reduction in carotenoid levels is also observed during biofilm formation. Thermotropic measurements of Laurdan GP and DPH polarization, show a reduction of lipid packing at 37 °C for biofilms compared to stationary phase. We studied the effects of carotenoid content on DMPG and DPPG model membranes showing trends in thermotropic behavior consistent with those observed in bacterial isolates, indicating that carotenoids participate in modulating lipid packing. Additionally, bending elastic constant (k_c) measurements using vesicle fluctuation analysis (VFA) show that the presence of carotenoids can increase membrane bending rigidity. The antimicrobial peptide Magainin H2 was less activity on liposomes composed of stationary phase compared to biofilms or exponential growth isolates. This study contributes to an understanding of how Staphylococcus aureus modulates the composition of its membrane lipids, and how those changes affect the biophysical properties of membranes, which in turn may play a role in its virulence and its resistance to different membrane-active antimicrobial agents.     

Carbon concentration and oxygen availability affect lipid and carotenoid production by carob pulp syrup‐grown Rhodosporidium toruloides NCYC 921

The simultaneous effect of oxygen availability and carbon source concentration on yeast lipid and carotenoid production has never been studied before. In this work, a Doehlert distribution design was used to study the simultaneous effect of carbon concentration and oxygen availability on Rhodosporidium toruloides NCYC 921 carotenoid and lipid production. A cheap industrial byproduct was used as carbon source (carob pulp syrup). A total sugar concentration of 106.3 g/L and a medium volume of 0.120 L induced the highest total carotenoid and total fatty acid productivities (4.60 μg/Lh and 0.029 g/Lh, respectively). Flow cytometry was used to assess yeast stress response under different cultivation conditions. The highest proportion of cells with permeabilised membrane (>20%) was induced when the cultivations were carried out at the highest sugar concentration studied (130.0 g/L) or when the culture reached the minimum final medium pH (4.60). The results showed that the total sugar concentration had a positive influence on the yeast biomass and carotenoid content, while the oxygen availability had little influence on the biomass concentration, but had a slight positive influence on the carotenoid content. Regarding the fatty acids, the two factors had a negative impact on the synthesis of these compounds.     

Reproductive character displacement shapes a spatially structured petal color polymorphism in Leavenworthia stylosa

Character displacement is a potentially important process driving trait evolution and species diversification. Floral traits may experience character displacement in response to pollinator‐mediated competition (ecological character displacement) or the risk of forming hybrids with reduced fitness (reproductive character displacement). We test these and alternative hypotheses to explain a yellow‐white petal color polymorphism in Leavenworthia stylosa, where yellow morphs are spatially associated with a white‐petaled congener (Leavenworthia exigua) that produces hybrids with complete pollen sterility. A reciprocal transplant experiment found limited evidence of local adaptation of yellow color morphs via increased survival and seed set. Pollinator observations revealed that Leavenworthia attract various pollinators that generally favor white petals and exhibit color constancy. Pollen limitation experiments showed that yellow petals do not alleviate competition for pollination. Interspecific pollinator movements were infrequent and low hybridization rates (～0.40–0.85%) were found in each morph, with natural rates likely being lower. Regardless, hybridization rates were significantly higher in white morphs of L. stylosa, yielding a small selection coefficient of s = 0.0042 against this phenotype in sympatry with L. exigua. These results provide support for RCD as a mechanism contributing to the pattern of petal color polymorphism in L. stylosa.     

Metabolic engineering of Pichia pastoris X-33 for lycopene production

As an alternative carotenoid producer, non-carotenogenic Pichia pastoris was chosen for a reddish carotenoid lycopene production because it can grow to high cell density without accumulation of ethanol and utilize various classes of organic materials such as methanol as carbon sources. Two synthetic lycopene-pathway plasmids, pGAPZB-EBI* and pGAPZB-EpBpI*p, were designed and constructed. The pGAPZB-EpBpI*p plasmid encoded three carotenogenic enzymes that were engineered to be targeted into peroxisomes of P. pastoris whereas the pGAPZB-EBI* plasmid encoded non-targeted enzymes. After both plasmids were transformed into P. pastoris, the lycopene-producing clone containing the pGAPZB-EpBpI*p plasmid, referred to as Ω, was selected and used for further optimization study. Of the carbon sources tested, glucose resulted in the highest level of lycopene production in complex and minimal media. Batch fermentation of the Ω clone resulted in the production of 4.6 mg-lycopene/g-DCW, with a concentration of 73.9 mg/l of lycopene in minimal medium. For the first time non-carotenogenic yeast P. pastoris was metabolically engineered by heterologously expressing lycopene-pathway enzymes and the lycopene concentration of 73.9 mg/l was obtained. This serves as a basis for the development of biological process for carotenoids using P. pastoris at a commercial production level.