Photosynthetic Capacity and Quantum Requirement of Three Secondary Mutants of Scenedesmus obliquus with Deletions in Carotenoid Biosynthesis*

Photosynthetic capacity and quantum requirement of photosynthesis were evaluated in three secondary mutants of Scenedesmus obliquus possessing specific blocks in carotenoid biosynthesis. These were derived from the mutant, C-2 A', a strain which develops chlorophyll only in the light. All strains were capable of a normal and rapid production of chlorophyll and the development of a functional photosynthetic apparatus when exposed to light. LHC-II levels in the mutants lacking the β,ε-carotenoids (strains C-2 A'-34,1 and C-2 A'-67, 3b) were considerably reduced in fully greened cells but normal in the β,β-epoxycarotenoid deficient-only strain (C-2 A'-67,1) (Bishop, 1996). The maximum photosynthetic capacity and the quantum efficiency (at λ=682nm) of photosynthesis of cells of C-2A'-34,1 and C-2 A'-67,1 showed no significant changes when compared to the original parent strain, C-2 A'. However, the quantum requirement of the strain lacking both types of carotenoids, C-2 A'-67,3b, was slightly increased. It is of particular interest that both strains lacking the β,ε-carotenoids also show a preferential loss of the oligomeric form of the LHC and its associated chlorophylls. The potential requirement of the different carotenoids in maintenance of photosynthetic efficiency in Scenedesmus is discussed.     

Changes in Compositional Properties during Fruit Development and On-Tree Ripening of Two Common Apricot (Prunus armeniaca L.) Cultivars

The objective of the present study was to investigate the variations in some major primary (sugars and organic acids) and secondary (phenolics, β-carotene) metabolite contents during fruit development and ripening in two important apricot cultivars (Hacıhaliloğlu and Kabaaşı). The changes in the compositional properties of two apricot cultivars were monitored during fruit development with one-week intervals from 56 to 119 days after blossom. During fruit development, the contents of organic acids and phenolics decreased whereas that of sucrose and sorbitol increased. p-Coumaric acid was the only phenolic compound which increased in concentration during fruit development regardless of the cultivar. The content of the other phenolic compounds decreased in a cultivar-dependent manner. The β-carotene content of the cultivars showed distinct patterns of change such that 3 fold increase in β-carotene content of Kabaaşı cultivar was observed whereas the β-carotene content of the Hacıhaliloğlu cultivar did not show any significant change during fruit development.     

Allelopathic activities of three carotenoids,neoxanthin, crocin and β-carotene,assayed using protoplast co-culture method with digital image analysis

Allelopathic activities of three carotenoids of a natural pigment group, neoxanthin, crocin and β-carotene, were assayed by the protoplast co-culture method with digital image analysis (DIA-PP method). Effects on three different growth stages of lettuce protoplasts, i.e., cell wall formation, cell division, and yellow pigment accumulation, were investigated using 96-well culture plates. Cell division was inhibited 65–95% by all three carotenoids at 33–100 µM. Inhibition of cell division stage was stronger than at the cell wall formation stage in neoxanthin, and the water-soluble carotenoid, crocin, whose yellow pigment was incorporated into the vacuole of lettuce protoplasts. Neoxanthin at 33 µM and crocin at higher than 100 µM inhibited more than 100% of the yellow pigment accumulation. By contrast, at low concentrations (0.01–1 µM) β-carotene stimulated growth at the cell division stage. At high concentrations of β-carotene (100–500 µM), inhibition was prominent at all three stages, and also in neighboring wells of zero control, which suggested emission of a volatile compound by β-carotene. They were compared with the report of the volatile compound, tulipalin A. Differences in patterns of inhibition of carotenoids on lettuce protoplast growth were compared with reports of another natural pigment, anthocyanin, and anthocyanin-containing red callus cultured in the light, and with that of neoxanthin-containing yellow callus cultured in the dark.     

Creating Carotenoid Diversity in E. coli Cells using Combinatorial and Directed Evolution Strategies

Carotenoids represent a structurally diverse class of pigments with important biological functions and commercial applications. Biosynthesis of carotenoids has been studied on a molecular level for the core pathways and recombinant hosts have been engineered for heterologous carotenoid production. This paper summarizes our efforts on accessing novel carotenoid compounds in engineered E. coli by altering the catalytic activities of enzymes using in vitro evolution, by exploring the catalytic promiscuity of known carotenoid enzymes and by mining for novel enzymes in microbial genome sequences.     

Floral Pollen Bioactive Properties and Their Synergy in Honeybee Pollen

Honeybee pollen (HBP) is a mixture of floral pollen collected by honeybees near the hive. It is characterized by a composition rich in phenolic compounds, carotenoids and vitamins that act as free radicals scavengers, conferring antioxidant and antibacterial capacity to the matrix. These bioactive properties are related to the botanical origin of the honeybee pollen. Honeybee pollen samples were collected from different geographical locations in central Chile, and their total carotenoid content, polyphenols profile by HPLC/MS/MS, DPPH radical scavenging capacity, and antimicrobial capacity against S. pyogenes, E. coli, S. aureus, and P. auriginosa strains were evaluated. Our results showed a good carotenoids content and polyphenols composition, while antioxidant capacity presented values between 0–95 % for the scavenging effect related to the botanical origin of the samples. Inhibition diameter for the different strains presented less variability among the samples, Furthermore, binary mixtures representing the two most abundant species in each HBP were prepared to assess the synergy effect of the floral pollen (FP) present in the samples. Data shows an antagonist effect was observed when assessing the carotenoid content, and a synergy effect often presents for antimicrobial and antioxidant capacity for bee pollen samples. The bioactive capacities of the honeybee pollen and their synergy effect could apply to develop new functional ingredients for the food industry.     

Role of nitrogen in the photoinduction of protoperithecia and carotenoids in Neurospora crassa

Nitrogen, as KNO₃ or NH₄NO₃, can inhibit the photoinduction of protoperithecia in Neurospora crassa when present in the medium at a high concentration but does not inhibit the photoinduction of carotenoids. The point at which the presence of high nitrogen levels is no longer inhibitory is 5 h after illumination.Abbreviations al albino mutant - wc white-collar mutant - WM Westergaard and Mitchell (1947) medium Dedicated to Professor Wilhelm Nultsch in honour of his 60th birthday     

Lactucaxanthin,an ε,ε-carotene-3,3′-diol from Lactuca sativa

Chemical and spectroscopic evidence including ¹H NMR and CD is presented, demonstrating the (3R,6R,3′R,6′R)-ε,ε-carotene-3,3′-diol structure of a new carotenoid, lactucaxanthin. Lactucaxanthin, isolated from Lactuca sativa, is the sixth chiral isomer encountered in nature ofthe ten possible chiral isomers of ε,ε-carotene-3,3?diol. In achemosystematic screening,lactucaxanthin was restricted to Lactuca and a few closely related genera within the tribe Cichorieae of the Compositae.     

Effect of dietary zinc level on serum carotenoid levels,body and shank pigmentation of chickens after experimental infection with coccidia

Abstract

Two experiments were conducted to test the effects of a dietary zinc amino acid complex (Zn-AA) and an anticoccidial drug on Eimeria acervulina or Eimeria tenella infections. In each experiment, 288 day-old Three-Yellow-Chickens were used in a 2 × 3 factorial experimental design. Six groups were arranged randomly to receive three levels of Zn-AA (0, 40, or 80 mg/kg) alone or with salinomycin (60 mg/kg). Additionally an uninfected group was set as negative control. At the age of 21 days birds in Exp. 1 were inoculated with 3 · 10⁴ sporulated E. acervulina oocysts, while birds in Exp. 2 were inoculated with 1.5 · 10⁴ sporulated E. tenella oocysts. In Exp. 1, E. acervulina did not suppress growth performance significantly, but in groups without salinomycin it significantly reduced serum carotenoid levels on day 7 after inoculation and body and shank pigmentation on day 42. Salinomycin medication maintained serum carotenoids and visual colour of inoculated birds, but Zn-AA did not influence these parameters. In Exp. 2, growth performances of infected and uninfected chickens were similar. Infection decreased to only serum carotenoid levels on day 14 after infection, and colour scores on day 42 in the inoculated group without salinomycin and Zn-AA supplementation. The birds that received Zn-AA had significantly higher serum carotenoid levels and colour scores than those that did not. Although supplementation of Zn-AA cannot avoid coccidial damage of caecum, it prevents the reduction of serum carotenoids and pigmentation of Three-Yellow-Chicken infected with E. tenella, but not after infection with E. avervulina. The interactive effects between Zn-AA and salinomycin on growth performance and pigmentation were not significant.     

Catalytic properties of the expressed acyclic carotenoid 2-ketolases from Rhodobacter capsulatus and Rubrivivax gelatinosus

Purple photosynthetic bacteria synthesize the acyclic carotenoids spheroidene and spirilloxanthin which are ketolated to spheroidenone and 2,2′-diketospirilloxanthin under aerobic growth. For the studies of the catalytic reaction of the ketolating enzyme, the crtA genes from Rubrivivax gelatinosus and Rhodobacter capsulatus encoding acyclic carotenoid 2-ketolases were expressed in Escherichia coli to functional enzymes. With the purified enzyme from the latter, the requirement of molecular oxygen and reduced ferredoxin for the catalytic activity was determined. Furthermore, the putative intermediate 2-HO-spheroidene was in vitro converted to the corresponding 2-keto product. Therefore, a monooxygenase mechanism involving two consecutive hydroxylation steps at C-2 were proposed for this enzyme. By functional pathway complementation studies in E. coli and enzyme kinetic studies, the product specificity of both enzymes were investigated. It appears that the ketolases could catalyze most intermediates and products of the spheroidene and spirilloxanthin pathway. This was also the case for the enzyme from Rba. capsulatus from which spirilloxanthin synthesis is absent. In general, the ketolase of Rvi. gelatinosus had a better specificity for spheroidene, HO-spheroidene and spirilloxanthin as substrates than the ketolase from Rba. capsulatus.     

Yellow plumage colour of Great Tits Parus major correlates with changing temperature and precipitation

Weather is known to affect the phenology and behaviour of birds, but weather-related changes of phenotypic traits involved in communication have received little attention. Using an 8-year dataset, we investigated links between carotenoid-based reflectance of the freshly moulted breast of Great Tits Parus major, weather during the moulting period and food availability during the preceding breeding season, and we investigated interannual changes. In both sexes, we found a change of colour expression to more saturated and darker yellow over the study period in parallel with increasingly dry and warm weather during moult. These results indicate that the expression of traits playing roles in communication may be controlled by weather and may therefore shift in response to changing climate.