Red Ketocarotenoids Research Articles

Early Oxidative Stress May Prevent a Red Ornament From Signaling Longevity.

Harsh early environmental conditions can exert delayed, long-lasting effects on phenotypes, including reproductive traits such as sexual signals. Indeed, adverse early conditions can accelerate development, increasing oxidative stress that may, in turn, impact adult sexual signals. Among signals, colorations produced by red ketocarotenoids seem to depend on mitochondrial functioning. Hence, they could reveal individual cell respiration efficiency. It has been hypothesized that these traits are unfalsifiable "index" signals of condition due to their deep connection to individual metabolism. Since mitochondrial dysfunction is frequently linked to aging, red ketocarotenoid-based ornaments could also be good signals of a critical fitness component: longevity. We tested this red color per longevity correlation in captive zebra finches. In addition, we experimentally decreased the synthesis of glutathione (a critical intracellular antioxidant) during the first days of the birds' life to resemble harsh early environmental conditions (e.g., undernutrition). Longevity was recorded until the death of the last bird (almost 9 years). Males, but not females, exhibiting a redder bill in early adulthood lived longer than males with paler bills, which agrees with some precedent studies. However, such bill redness-longevity connection was absent among males with inhibited glutathione synthesis. These findings may suggest that environmental factors can alter the reliability of red ketocarotenoid-based sexual signals, making them less unfalsifiable than believed.

Multiple Routes to Color Convergence in a Radiation of Neotropical Poison Frogs.

Convergent evolution is defined as the independent evolution of similar phenotypes in different lineages. Its existence underscores the importance of external selection pressures in evolutionary history, revealing how functionally similar adaptations can evolve in response to persistent ecological challenges through a diversity of evolutionary routes. However, many examples of convergence, particularly among closely related species, involve parallel changes in the same genes or developmental pathways, raising the possibility that homology at deeper mechanistic levels is an important facilitator of phenotypic convergence. Using the genus Ranitomeya, a young, color-diverse radiation of Neotropical poison frogs, we set out to 1) provide a phylogenetic framework for this group, 2) leverage this framework to determine if color phenotypes are convergent, and 3) to characterize the underlying coloration mechanisms to test whether color convergence occurred through the same or different physical mechanisms. We generated a phylogeny for Ranitomeya using ultraconserved elements and investigated the physical mechanisms underlying bright coloration, focusing on skin pigments. Using phylogenetic comparative methods, we identified several instances of color convergence, involving several gains and losses of carotenoid and pterin pigments. We also found a compelling example of nonparallel convergence, where, in one lineage, red coloration evolved through the red pterin pigment drosopterin, and in another lineage through red ketocarotenoids. Additionally, in another lineage, "reddish" coloration evolved predominantly through structural color mechanisms. Our study demonstrates that, even within a radiation of closely related species, convergent evolution can occur through both parallel and nonparallel mechanisms, challenging the assumption that similar phenotypes among close relatives evolve through the same mechanisms.

Microbial astaxanthin: from bioprocessing to the market recognition.

The attractive biological properties and health benefits of natural astaxanthin (AXT), including its antioxidant and anti-carcinogenic properties, have garnered significant attention from academia and industry seeking natural alternatives to synthetic products. AXT, a red ketocarotenoid, is mainly produced by yeast, microalgae, wild or genetically engineered bacteria. Unfortunately, the large fraction of AXT available in the global market is still obtained using non-environmentally friendly petrochemical-based products. Due to the consumers concernsabout synthetic AXT, the market of microbial-AXT is expected to grow exponentially in succeeding years. This review provides a detailed discussion of AXT's bioprocessing technologies and applications as a natural alternative to synthetic counterparts. Additionally, we present, for the first time, a very comprehensive segmentation of the global AXT market and suggest research directions to improve microbial production using sustainable and environmentally friendly practices. KEY POINTS: • Unlock the power of microorganisms for high value AXT production. • Discover the secrets to cost-effective microbial AXT processing. • Uncover the future opportunities in the AXT market.

A mechanism for red coloration in vertebrates

Red coloration is a salient feature of the natural world. Many vertebrates produce red color by converting dietary yellow carotenoids into red ketocarotenoids via an unknown mechanism. Here, we show that two enzymes, cytochrome P450 2J19 (CYP2J19) and 3-hydroxybutyrate dehydrogenase 1-like (BDH1L), are sufficient to catalyze this conversion. In birds, both enzymes are expressed at the sites of ketocarotenoid biosynthesis (feather follicles and red cone photoreceptors), and genetic evidence implicates these enzymes in yellow/red color variation in feathers. In fish, the homologs of CYP2J19 and BDH1L are required for ketocarotenoid production, and we show that these enzymes are sufficient to produce ketocarotenoids in cell culture and when ectopically expressed in fish skin. Finally, we demonstrate that the red-cone-enriched tetratricopeptide repeat protein 39B (TTC39B) enhances ketocarotenoid production when co-expressed with CYP2J19 and BDH1L. The discovery of this mechanism of ketocarotenoid biosynthesis has major implications for understanding the evolution of color diversity in vertebrates.

Wild common crossbills produce redder body feathers when their wings are clipped

BackgroundThe animal signaling theory posits that conspicuous colorations exhibited by many animals have evolved as reliable signals of individual quality. Red carotenoid-based ornaments may depend on enzymatic transformations (oxidation) of dietary yellow carotenoids, which could occur in the inner mitochondrial membrane (IMM). Thus, carotenoid ketolation and cell respiration could share the same biochemical pathways. Accordingly, the level of trait expression (redness) would directly reveal the efficiency of individuals’ metabolism and, hence, the bearer quality in an unfalsifiable way. Different avian studies have described that the flying effort may induce oxidative stress. A redox metabolism modified during the flight could thus influence the carotenoid conversion rate and, ultimately, animal coloration. Here, we aimed to infer the link between red carotenoid-based ornament expression and flight metabolism by increasing flying effort in wild male common crossbills Loxia curvirostra (Linnaeus). In this order, 295 adult males were captured with mist nets in an Iberian population during winter. Approximately half of the birds were experimentally handicapped through wing feather clipping to increase their flying effort, the other half being used as a control group. To stimulate the plumage regrown of a small surface during a short time-lapse, we also plucked the rump feathers from all the birds.ResultsA fraction of the birds with fully grown rump feathers (34 individuals) could be recaptured during the subsequent weeks. We did not detect any significant bias in recovery rates and morphological variables in this reduced subsample. However, among recaptured birds, individuals with experimentally impaired flying capacity showed body mass loss, whereas controls showed a trend to increase their weight. Moreover, clipped males showed redder feathers in the newly regrown rump area compared to controls.ConclusionsThe results suggest that wing-clipped individuals could have endured higher energy expenditure as they lost body mass. Despite the small sample size, the difference in plumage redness between the two experimental groups would support the hypothesis that the flying metabolism may influence the redox enzymatic reactions required for converting yellow dietary carotenoids to red ketocarotenoids.

Engineering an oilseed crop for hyper-accumulation of carotenoids in the seeds without using a traditional marker gene.

Ketocarotenoids were synthesized successfully in Camelina sativa seeds by genetic modification without using a traditional selection marker genes. This method provided an interesting tool for metabolic engineering of seed crops. Camelina sativa (L.) Crantz is an important oil crop with many excellent agronomic traits. This model oil plant has been exploited to accumulate value-added bioproducts using genetic manipulation that depends on antibiotic- or herbicide-based selection marker genes (SMG), one of the major concerns for genetically modified foods. Here we reported metabolic engineering of C. sativa to synthesize red ketocarotenoids that could serve as a reporter to visualize transgenic events without using a traditional SMG. Overexpression of a non-native β-carotene ketolase gene coupled with three other carotenogenous genes (phytoene synthase, β-carotene hydroxylase, and Orange) in C. sativa resulted in production of red seeds that were visibly distinguishable from the normal yellow ones. Constitutive expression of the transgenes led to delayed plant development and seed germination. In contrast, seed-specific transformants demonstrated normal growth and seed germination despite the accumulation of up to 70-fold the level of carotenoids in the seeds compared to the controls, including significant amounts of astaxanthin and keto-lutein. As a result, the transgenic seed oils exhibited much higher antioxidant activity. No significant changes were found in the profiles of fatty acids between transgenic and control seeds. This study provided an interesting tool for metabolic engineering of seed crops without using a disputed SMG.

Bigger or long-winged male common crossbills exhibit redder carotenoid-based plumage coloration.

Carotenoid-based ornaments are often considered reliable (honest) individual condition signals because their expression implies physiological costs unaffordable for low-quality animals (handicap signals). Recently, it has been suggested that efficient cell respiration is mandatory for producing red ketocarotenoids from dietary yellow carotenoids. This implies that red colorations should be entirely unfalsifiable and independent of expression costs (index signals). In a precedent study, male common crossbills, Loxia curvirostra, showing a red plumage reported higher apparent survival than those showing yellowish-orange colors. The plumage redness in this species is due to ketocarotenoid accumulation in feathers. Here, we correlated the male plumage redness (a 4-level visual score: yellow, patchy, orange, and red) and the body morphology in more than 1,000 adult crossbills captured in 3 Iberian localities to infer the mechanisms responsible for color evolution. A principal component analysis summarized morphometry of 10 variables (beak, wing, tarsus length, etc.). The overall body size (PC1) and the length of flight feathers regarding body size (PC3) showed significant positive relationships with plumage redness. Plumage redness was barely correlated with bill shape measures, suggesting no constraint in acquiring carotenoids from pine cones. However, large body sizes or proportionally long flying feathers could help carotenoid acquisition via social competition or increased foraging ranges. Proportionally longer flight feathers might also be associated with a specific cell respiration profile that would simultaneously favor flying capacities and enzymatic transformations needed for ketocarotenoid synthesis. Such a phenotypic profile would agree with the hypothesis of ketocarotenoid-based colors acting as individual quality index signals.

Development and genetics of red coloration in the zebrafish relative Danio albolineatus.

Animal pigment patterns play important roles in behavior and, in many species, red coloration serves as an honest signal of individual quality in mate choice. Among Danio fishes, some species develop erythrophores, pigment cells that contain red ketocarotenoids, whereas other species, like zebrafish (D. rerio) only have yellow xanthophores. Here, we use pearl danio (D. albolineatus) to assess the developmental origin of erythrophores and their mechanisms of differentiation. We show that erythrophores in the fin of D. albolineatus share a common progenitor with xanthophores and maintain plasticity in cell fate even after differentiation. We further identify the predominant ketocarotenoids that confer red coloration to erythrophores and use reverse genetics to pinpoint genes required for the differentiation and maintenance of these cells. Our analyses are a first step toward defining the mechanisms underlying the development of erythrophore-mediated red coloration in Danio and reveal striking parallels with the mechanism of red coloration in birds.

Testing the carotenoid-based sexual signalling mechanism by altering CYP2J19 gene expression and colour in a bird species.

Ornaments can evolve to reveal individual quality when their production/maintenance costs make them reliable as 'signals' or if their expression level is intrinsically linked to condition by some unfalsifiable mechanism (indices). The latter has been mostly associated with traits constrained by body size. In red ketocarotenoid-based colorations, that link could, instead, be established with cell respiration at the inner mitochondrial membrane (IMM). The production mechanism could be independent of resource (yellow carotenoids) availability, thus discarding costs linked to allocation trade-offs. A gene coding for a ketolase enzyme (CYP2J19) responsible for converting dietary yellow carotenoids to red ketocarotenoids has recently been described. We treated male zebra finches with an antioxidant designed to penetrate the IMM (mitoTEMPO) and a thyroid hormone (triiodothyronine) with known hypermetabolic effects. Among hormone controls, MitoTEMPO downregulated CYP2J19 in the bill (a red ketocarotenoid-based ornament), supporting the mitochondrial involvement in ketolase function. Both treatments interacted when increasing hormone dosage, indicating that mitochondria and thyroid metabolisms could simultaneously regulate coloration. Moreover, CYP2J19 expression was positively correlated to redness but also to yellow carotenoid levels in the blood. However, treatment effects were not annulated when controlling for blood carotenoid variability, which suggests that costs linked to resource availability could be minor.

CYP2J19 mediates carotenoid colour introgression across a natural avian hybrid zone.

It has long been of interest to identify the phenotypic traits that mediate reproductive isolation between related species, and more recently, the genes that underpin them. Much work has focused on identifying genes associated with animal colour, with the candidate gene CYP2J19 identified in laboratory studies as the ketolase converting yellow dietary carotenoids to red ketocarotenoids in birds with red pigments. However, evidence that CYP2J19 explains variation between red and yellow feather coloration in wild populations of birds is lacking. Hybrid zones provide the opportunity to identify genes associated with specific traits. Here we investigate genomic regions associated with colour in red-fronted and yellow-fronted tinkerbirds across a hybrid zone in southern Africa. We sampled 85 individuals, measuring spectral reflectance of forecrown feathers and scoring colours from photographs, while testing for carotenoid presence with Raman spectroscopy. We performed a genome-wide association study to identify associations with carotenoid-based coloration, using double-digest RAD sequencing aligned to a short-read whole genome of a Pogoniulus tinkerbird. Admixture mapping using 104,933 single nucleotide polymorphisms (SNPs) identified a region of chromosome 8 that includes CYP2J19 as the only locus with more than two SNPs significantly associated with both crown hue and crown score, while Raman spectra provided evidence of ketocarotenoids in red feathers. Asymmetric backcrossing in the hybrid zone suggests that yellow-fronted females mate more often with red-fronted males than vice versa. Female red-fronted tinkerbirds mating assortatively with red-crowned males is consistent with the hypothesis that converted carotenoids are an honest signal of quality.

A review on the application and effect of carotenoids with respect to canthaxanthin in the culture of fishes and crustaceans

Fisheries sector serves as a substantial source of income and employment for a huge number of individuals around the world and it comparatively remains a crucial source of food and nutrition. Culture of aquatic species for food and ornamental purpose has been on increasing trend. High-performance feeds are formulated for the growth and progress of the cultured animals, usually supplemented with carotenoids of natural and synthetic origin. The market acceptability of ornamental fishes depends on pigmentation, one of the considerable attributes for determining quality. Carotenoids are a group of fat-soluble pigments broadly distributed in nature and are well recognized for their bright red, yellow, and orange colours. Studies on these carotenoids over decades have shown that these carotenoids are beneficial for the fish and crustacean aquaculture and also in the ornamental trade by imparting pigmentation. Canthaxanthin falls under the category of red keto-carotenoid and is one of the most important xanthophylls in the business perspective due to its extensive application in the field, next to astaxanthin. A large portion of the commercial canthaxanthin available in the market are chemically synthesized as the naturally available canthaxanthin are found in very lower concentrations. In addition, to a lesser extent, they are also implicated in the growth performances, digestion and as an anti-oxidant. This review updates the ongoing advancement on canthaxanthin on the dietary utilisation, storage, pigmentation and other enhanced growth performances on the aquaculture of food fish, crustacean and ornamental fishes.

Testing the shared-pathway hypothesis in the carotenoid-based coloration of red crossbills.

The mechanisms involved in the production of red carotenoid-based ornaments of vertebrates are still poorly understood. These colorations often depend on enzymatic transformations (ketolation) of dietary yellow carotenoids, which could occur in the inner mitochondrial membrane (IMM). Thus, carotenoid ketolation and cell respiration could share biochemical pathways, favoring the evolution of ketocarotenoid-based ornaments as reliable indices of individual quality under sexual selection. Captive male red crossbills (Loxia curvirostra Linnaeus) were exposed to redox-active compounds designed to penetrate and act in the IMM: an ubiquinone (mitoQ) or a superoxide dismutase mimetic (mitoTEMPO). MitoQ can act as an antioxidant but also distort the IMM structure, increasing mitochondrial free radical production. MitoQ decreased yellow carotenoids and tocopherol levels in blood, perhaps by being consumed as antioxidants. Contrarily, mitoTEMPO-treated birds rose circulating levels of the second most abundant ketocarotenoid in crossbills (i.e., canthaxanthin). It also increased feather total red ketocarotenoid concentration and redness, but only among those birds exhibiting a redder plumage at the start of the study, that is, supposedly high-quality individuals. The fact that mitoTEMPO effects depended on original plumage color suggests that the red-ketocarotenoid-based ornaments indicate individual quality as mitochondrial function efficiency. The findings would thus support the shared pathway hypothesis.

A ketocarotenoid-based colour polymorphism in the Sira poison frog Ranitomeya sirensis indicates novel gene interactions underlying aposematic signal variation.

The accumulation of red ketocarotenoids is an important component of coloration in many organisms, but the underlying mechanisms are poorly understood. In some organisms, ketocarotenoids are sequestered from the diet and can accumulate when enzymes responsible for carotenoid breakdown are disrupted. In other organisms, ketocarotenoids are formed endogenously from dietary precursors via oxidation reactions carried out by carotenoid ketolase enzymes. Here, we study the genetic basis of carotenoid coloration in an amphibian. We demonstrate that a red/yellow polymorphism in the dendrobatid poison frog Ranitomeya sirensis is due to the presence/absence of ketocarotenoids. Using whole-transcriptome sequencing of skins and livers, we found that a transcript encoding a cytochrome P450 enzyme (CYP3A80) is expressed 3.4-fold higher in livers of red frogs versus yellow. As CYP3A enzymes are known carotenoid ketolases in other organisms, our results point to CYP3A80 as a strong candidate for a carotenoid ketolase in amphibians. Furthermore, in red frogs, the transcript encoding the carotenoid cleavage enzyme BCO2 is expressed at a low level or as a splice variant lacking key catalytic amino acids. This suggests that BCO2 function may be disrupted in red frogs, providing a mechanism whereby the accumulation of ketocarotenoids and their dietary precursors may be enhanced.

Red carotenoids and associated gene expression explain colour variation in frillneck lizards.

A long-standing hypothesis in evolutionary ecology is that red-orange ornamental colours reliably signal individual quality owing to limited dietary availability of carotenoids and metabolic costs associated with their production, such as the bioconversion of dietary yellow carotenoids to red ketocarotenoids. However, in ectothermic vertebrates, these colours can also be produced by self-synthesized pteridine pigments. As a consequence, the relative ratio of pigment types and their biochemical and genetic basis have implications for the costs and information content of colour signals; yet they remain poorly known in most taxonomic groups. We tested whether red- and yellow-frilled populations of the frillneck lizard, Chlamydosaurus kingii, differ in the ratio of different biochemical classes of carotenoid and pteridine pigments, and examined associated differences in gene expression. We found that, unlike other squamate reptiles, red hues derive from a higher proportion of ketocarotenoids relative to both dietary yellow carotenoids and to pteridines. Whereas red frill skin showed higher expression of several genes associated with carotenoid metabolism, yellow frill skin showed higher expression of genes associated with steroid hormones. Based on the different mechanisms underlying red and yellow signals, we hypothesize that frill colour conveys different information in the two populations. More generally, the data expand our knowledge of the genetic and biochemical basis of colour signals in vertebrates.

Computational fluid dynamics simulation in scaling-up of airlift photobioreactor for astaxanthin production

The unicellular green microalga Haematococcus pluvialis accumulates large amounts of the red ketocarotenoid astaxanthin. Aiming to cultivate these microalgae with high astaxanthin efficiency, cultivations were scaled-up from 1000mL bottle to 2L and 8L airlift photobioreactor using volumetric power consumption rate (W/m3) as scale up strategy. After cultivations, computational fluid dynamics (CFD) simulation was used to investigate the flow patterns, mixing efficiency and gas holdup profile within the 2L photobioreactor. At the end, astaxanthin content was enhanced with increasing the cultivation volume and highest astaxanthin amount of 49.39 ± 1.64mg/g cell was obtained in 8L photobioreactor. Hydrodynamic characteristics of photobioreactor was simulated and gas holdup showed difference between the riser and the downcomer regions. Velocity profiles of air and medium had higher values inside the draft tube than obtained in downcomer region. However liquid circulation was achieved from draft tube to the downcomer, mixing was not provided effectively considering the turbulence kinetic energy. For the further research, some developments about column configuration, sparger diameter may be necessary to enhance the mixing characteristics.

Polyethyleneimine-induced astaxanthin accumulation in the green alga Haematococcus pluvialis by increased oxidative stress

The unicellular green microalga Haematococcus pluvialis accumulates large amounts of the red ketocarotenoid astaxanthin under stress conditions such as nitrogen deficiency. In this study, we discovered an astaxanthin accumulation in H.pluvialis cells by the addition of a synthetic cationic polymer, polyethyleneimine (PEI), into the cell culture. With an increase in PEI amount, amount of astaxanthin accumulation was increased. To investigate the mechanism for the accumulation of astaxanthin by the addition of PEI in H.pluvialis cells, we measured a localization of PEI in the cells and a production of reactive oxygen species. PEI was internalized in the cells through the negatively-charged cell walls, leading to excessive production of reactive oxygen species in the cells. Thus, the increased oxidative stress by cellular uptake of PEI resulted in the acceleration of astaxanthin accumulation in H.pluvialis.

Red coloration varies with dietary carotenoid access and nutritional condition in kittiwakes.

Carotenoid-based ornaments are common signaling features in animals. Although the mechanisms that link color-based signals to individual condition is key to understanding the evolution and function of these ornaments, they are most often poorly known. Several hypotheses have been posited. They include: (i) the role of foraging abilities on carotenoid acquisition and thereby carotenoid-based ornaments, and (ii) the role of internal processes linked to individual quality on the allocation and conversion of carotenoids in integuments. Here, we tested the influence of dietary carotenoid access versus internal process on gape coloration in black-legged kittiwakes (Rissa tridactyla). This seabird displays a vibrant red gape, whose coloration varies with individual quality in males and is due to the deposition of red ketocarotenoids, such as astaxanthin. We decreased hydroxycarotenoid and ketocarotenoid levels in plasma, but increased efficiency in internal processes linked to nutritional condition, by supplementing breeding males with capelin, a natural energy-rich fish prey. We found that, despite having lower carotenoid levels in plasma, supplemented birds developed redder coloration than control birds, but only in the year when dietary levels of astaxanthin in the natural diet were low. In contrast, in the astaxanthin-rich year, supplemented males had a less-red gape than unsupplemented birds. These results suggest that inter-individual differences in internal processes may be sufficient to maintain the honesty of gape coloration under conditions of low dietary astaxanthin levels. Nonetheless, when inter-individual variations in dietary astaxanthin levels are elevated (such as in the crustacean-rich year), carotenoid access seems a more limiting factor to the expression of gape coloration than internal processes. Therefore, our study revealed a complex mechanism of gape color production in kittiwakes, and suggests that the main factor maintaining the condition dependency of this ornaments may vary with environmental conditions and diet composition.

Carotenoid dynamics and lipid droplet containing astaxanthin in response to light in the green alga Haematococcus pluvialis

The unicellular green alga Haematococcus pluvialis accumulates large amounts of the red ketocarotenoid astaxanthin to protect against environmental stresses. Haematococcus cells that accumulate astaxanthin in the central part (green-red cyst cells) respond rapidly to intense light by distributing astaxanthin diffusively to the peripheral part of the cell within 10 min after irradiation. This response is reversible: when astaxanthin-diffused cells were placed in the dark, astaxanthin was redistributed to the center of the cell. Although Haematococcus possesses several pigments other that astaxanthin, the subcellular distribution and content of each pigment remain unknown. Here, we analyzed the subcellular dynamics and localization of major pigments such as astaxanthin, β-carotene, lutein, and chlorophylls under light irradiation using time-lapse and label-free hyperspectral imaging analysis. Fluorescence microscopy and freeze-fracture transmission electron microscopy showed that, preceding/following exposure to light, astaxanthin colocalized with lipid droplets, which moved from the center to the periphery through pathways in a chloroplast. This study revealed that photoresponse dynamics differed between astaxanthin and other pigments (chlorophylls, lutein, and β-carotene), and that only astaxanthin freely migrates from the center to the periphery of the cell through a large, spherical, cytoplasm-encapsulating chloroplast as a lipid droplet. We consider this to be the Haematococcus light-protection mechanism.

Non-steroidal anti-inflammatory drugs initiate morphological changes but inhibit carotenoid accumulation in Haematococcus pluvialis

The economic role of certain types of cysts is unquestionable, since the production of several valuable biomolecules is connected to the resting stages of algae, including the red ketocarotenoid astaxanthin. It is relatively well known, how adverse environmental conditions induce cyst formation and astaxanthin accumulation. In the contrary, there is very limited information about stressors inhibiting these processes. An undesirable consequence of increasing drug use of the human and veterinary medicine is the appearance of the drugs both in natural and in mains water. Therefore, to study the effects of micro-contaminants, e.g. pharmaceuticals to non-target aquatic organisms is a recent issue both from ecological and economical point of view. In this study, the effects of three non-steroidal anti-inflammatory drugs (NSAIDs: diclofenac, diflunisal and mefenamic acid) on growth, cyst formation and astaxanthin accumulation of the flagellated green alga Haematococcus pluvialis were investigated. All three drugs inhibited growth, inhibition ranged from 29 to 81% on the basis of vegetative cell numbers on the 14th day of the experiments. Higher concentrations of the drugs led to higher proportion of cysts, which exceeded 60% of total cell number to the 14th day in diclofenac and diflunisal treatments. On the contrary, astaxanthin contents of treated cultures were lower with the increasing drug concentration, the pigment was undetectable in the presence of 0.075 and 0.05 mg ml−1 diclofenac. Results of carotenoid and chlorophyll content analysis suggest more specific processes behind the observed phenomena than membrane damage. Furthermore, the different phenomena or different extents of the same phenomena suggest that NSAIDs with diverse chemical structures may have different target points in physiological processes. Our results clearly show that NSAIDs could have much wider effective spectra than expected, long-term effects on microalgae might have unexpected ecological or economical consequences due to continuous exposure to these chemicals.

Effects of salt stress on astaxanthin accumulation, gene expression of astaxanthin synthesis-related enzymes, and antioxidant indices in Haematococcus pluvialis

PDF HTML阅读 XML下载 导出引用 引用提醒 盐胁迫对雨生红球藻虾青素累积、虾青素合成相关酶基因表达和抗氧化指标的影响 DOI: 作者: 作者单位: 1. 河南师范大学水产学院, 河南 新乡 453007;2. 宁德师范学院 生物系, 福建 宁德 352100;3. 河南师范大学 生命科学学院, 河南 新乡 453007 作者简介: 江红霞(1974-),女,副教授,研究方向为水生生物资源与环境.E-mail:jianghongxia2007@126.com 通讯作者: 中图分类号: S96 基金项目: 河南省重点科技攻关项目（102102210181）；河南省水产学重点学科基金项目（2012）. Effects of salt stress on astaxanthin accumulation, gene expression of astaxanthin synthesis-related enzymes, and antioxidant indices in Haematococcus pluvialis Author: Affiliation: 1. College of Fisheries, Henan Normal University, Xinxiang 453007, China;2. Department of Biology, Ningde Normal University, Ningde 352100, China;3. College of Life Sciences, Henan Normal University, Xinxiang 453007, China Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:为探讨盐胁迫对雨生红球藻（）虾青素合成的影响与机理，以及雨生红球藻各抗氧化机制之间的关系，本研究采用生化和分子生物学方法研究了不同浓度（0.04 mol/L、0.08 mol/L、0.12 mol/L和0.16 mol/L）和不同时间（3 d、6 d和9 d）的盐（NaCl）胁迫对雨生红球藻生长、虾青素积累、番茄红素-胡萝卜素酮化酶（Bkt）基因表达、超氧化物歧化酶（SOD）、过氧化氢酶（CAT）和谷胱甘肽过氧化物酶（GSH-Px）的活性以及丙二醛（MDA）含量的影响。结果表明，各胁迫时间的雨生红球藻的密度均随着盐胁迫浓度的增加而不断下降，在盐胁迫的第9天，雨生红球藻的死亡率和孢子比例均随着盐胁迫浓度的增加而不断升高；雨生红球藻虾青素含量、基因表达量均随着盐胁迫浓度和时间的增加而不断提高；雨生红球藻SOD、CAT和GSH-Px活性以及MDA含量在不同浓度和不同时间的盐胁迫下与对照组（0.00 mol/L NaCl）相比均升高，且在不同时间的0.12 mol/L NaCl胁迫下与对照组相比均显著升高（基因表达量在盐胁迫的早期（第3天）和中期（第6天）阶段较低，在盐胁迫的后期（第9天）阶段较高，而SOD、CAT和GSH-Px活性以及MDA含量在盐胁迫的早期和中期阶段较高，在盐胁迫的后期阶段较低。实验结果说明了适当浓度和时间的盐胁迫能促进雨生红球藻累积虾青素，雨生红球藻在盐胁迫下主要是通过提高虾青素合成相关酶基因的转录水平来促进虾青素的合成，其虾青素和抗氧化酶的抗氧化活性可能互为补充，共同保护雨生红球藻免受盐胁迫的氧化损伤。 Abstract:(Chlorophyceae, Order Volvocales), a freshwater green microalgal species, has commercial value owing to its ability to accumulate high concentrations of astaxanthin (up to 5% of dry weight). Astaxanthin (3,3'-dihydroxy--carotene-4,4'-dione) is a red ketocarotenoid which has many important biological functions, including antioxidant activity, regulation of immune responses, and disease resistance, and has the potential for application in the aquacultural, nutraceutical, pharmaceutical, and cosmetic industries. has a distinctive lifecycle as it exhibits a green motile stage and a red non-motile resting stage called an aplanospore. In general, astaxanthin accumulation in is restricted to the aplanospore stage. Astaxanthin is accumulated in extra-plastidic lipid vesicles as a secondary carotenoid, and it is believed to be synthesized in response to oxidative stress in the red aplanospore stage under unfavorable environmental conditions such as high light, temperature, and salinity, or low nutrient availability. Several enzymes such as lycopene -carotene ketolase (Bkt) are involved in the astaxanthin bios-y-n-thesis pathway in -carotene from lycopene, and CrtR-B and Bkt cat-alyze further steps leading to astaxanthin synthesis. Changes in expression of the genes encoding these three enzymes can critically affect the biosynthesis and accumulation of astaxanthin in . In addition, various ant-i-oxidant enzymes including superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) also have important protective effects for combating oxidative stress under unfavourable environmental conditions. We aimed to explore the effect of salt stress on astaxanthin accumulation in , by examining the mechanism of astaxanthin synthesis and the relationship between the different antioxidant mechanisms in at high salinity. We examined its growth rate; astaxanthin content; gene expression levels; SOD, CAT, and GSH-Px activities; and malondialdehyde (MDA) content at four salinity levels (0.04 mol/L, 0.08 mol/L, 0.12 mol/L, and 0.16 mol/L) over three timescales (3 days, 6 days, and 9 days). Our results showed that the density of decreased under increasing salinity over different periods of time, while its mortality rate and aplanospore proportion increased with increasing salt stress concentration by the ninth day of stress. Asta-xanthin content, gene expressions increased over time with increasing salinity. SOD, CAT, and GSH-Px activities and MDA content also increased in comparison to grown at the control level of 0 mol/L NaCl, and significantly increased at the 0.12 mol/L NaCl level ( gene expressions were lower during the early and mid-stages of salt stress (e.g., on the third and sixth days of observation), and increased by the ninth day. Meanwhile, SOD, CAT, and GSH-Px activities and MDA content were higher during early and mid-stage stress, but were lower by the ninth day. These results suggest that salt stress can improve astaxanthin accumulation over time in at the appropriate level of salt stress, despite its negative effects on growth. Astaxanthin synthesis in is promoted mainly through an increase in the transcription level of astaxanthin synthesis-related enzyme genes under salt stress, and the antioxid-ant activities of astaxanthin and antioxidant enzymes complement one other to protect from oxidative damage under salt stress. This study provides a new insight into the astaxanthin synthesis and antioxidant mechanisms in . 参考文献 相似文献 引证文献