Carotenoid Coloration Research Articles

Expression of a carotenoid-modifying gene and evolution of red coloration in weaverbirds (Ploceidae).

Red carotenoid colours in birds are widely assumed to be sexually selected quality indicators, but this rests on a very incomplete understanding of genetic mechanisms and honesty-mediating costs. Recent progress was made by the implication of the gene CYP2J19 as an avian carotenoid ketolase, catalysing the synthesis of red C4-ketocarotenoids from yellow dietary precursors, and potentially a major mechanism behind red coloration in birds. Here, we investigate the role of CYP2J19 in the spectacular colour diversification of African weaverbirds (Ploceidae), represented by five genera and 16 species: eight red, seven yellow and one without carotenoid coloration. All species had a single copy of CYP2J19, unlike the duplication found in the zebra finch, with high expression in the retina, confirming its function in colouring red oil droplets. Expression was weak or undetected in skin and follicles of pigment-depositing feather buds, as well as in beaks and tarsi, including those of the red-billed quelea. In contrast, the hepatic (liver) expression of CYP2J19 was consistently higher (>14-fold) in seven species with C4-ketocarotenoid coloration than in species without (including one red species), an association strongly supported by a phylogenetic comparative analysis. The results suggest a critical role of the candidate ketolase, CYP2J19, in the evolution of red C4-ketocarotenoid colour variation in ploceids. As ancestral state reconstruction suggests that ketocarotenoid coloration has evolved twice in this group (once in Euplectes and once in the Quelea/Foudia clade), we argue that while CYP2J19 has retained its ancestral role in the retina, it has likely been co-opted for red coloration independently in the two lineages, via increased hepatic expression.

Influence of process variables on the drum drying of mango pulp

ABSTRACTResponse surface methodology was used to evaluate the best process conditions in the drum drying of mango pulp regarding the physicochemical properties and nutrients content. The independent variables in the central composite rotatable design were: temperature (119–151°C) and residence time (9–41 s), while the concentrations of process additives used were: 3% corn starch and 0.5% glyceryl monostearate. Mathematical models for moisture content, total carotenoid content, and color parameters of the reconstituted pulp (a*, Hue, and ΔE) were obtained. The optimized conditions were combinations of residence time between 10 and 25 s, and temperature from 120 to 135°C, in which the flakes showed moisture content ranging from 2 to 5%, besides a more intense yellow color and total carotenoid retention between 90 and 96%.

Carotenoid coloration is related to fat digestion efficiency in a wild bird.

Some of the most spectacular visual signals found in the animal kingdom are based on dietarily derived carotenoid pigments (which cannot be produced de novo), with a general assumption that carotenoids are limited resources for wild organisms, causing trade-offs in allocation of carotenoids to different physiological functions and ornamentation. This resource trade-off view has been recently questioned, since the efficiency of carotenoid processing may relax the trade-off between allocation toward condition or ornamentation. This hypothesis has so far received little exploratory support, since studies of digestive efficiency of wild animals are limited due to methodological difficulties. Recently, a method for quantifying the percentage of fat in fecal samples to measure digestive efficiency has been developed in birds. Here, we use this method to test if the intensity of the carotenoid-based coloration predicts digestive efficiency in a wild bird, the house finch (Haemorhous mexicanus). The redness of carotenoid feather coloration (hue) positively predicted digestion efficiency, with redder birds being more efficient at absorbing fats from seeds. We show for the first time in a wild species that digestive efficiency predicts ornamental coloration. Though not conclusive due to the correlative nature of our study, these results strongly suggest that fat extraction might be a crucial but overlooked process behind many ornamental traits.

Discrimination of signal carotenoid content using multidimensional chromatic information

Red, orange, and yellow carotenoid-based ornaments, which are widely used as sexual signals in many birds, fish, and reptiles, are known to exhibit multidimensional chromatic variation as a result of both the concentration and relative proportions of different constituent carotenoids with differing spectral properties. This is thought to reflect intrinsic variation in signaler quality, making it a useful basis for female choice. However, whether females are able to discriminate relevant variation in carotenoid concentration and/or composition independently of each other, and of other phenotypic or behavior traits, and if so, how this mediates their choice, is poorly understood. Here, female 3-spined sticklebacks (Gasterosteus aculeatus) were presented with computer-animated courting males that varied exclusively in the appearance of their carotenoid-based coloration; specifically, each male’s signal provided a perceptual match for carotenoid coloration expressed by live males with known underlying carotenoid content, thereby providing a biologically-relevant signal while precluding confounding traits influencing female choice. Females were able to discriminate between prospective mates solely on the basis of perceived variation in the allocation of carotenoids to males’ sexual signals, and exhibited a strong preference for males with coloration indicative of higher concentrations of carotenoids in their signal, rather than in response to perceived variation in the relative proportion of constituent carotenoids. This has important implications for our understanding of male signaling strategies and the information content of carotenoid-based sexual signals.

Candidate gene sequencing and validation of SNP markers linked to carotenoid content in cassava (Manihot esculenta Crantz)

Cassava is a widely grown staple in Sub-Saharan Africa and consumed as a cheap source of calories, but the crop is deficient in micronutrients including pro-vitamin A carotenoids. This challenge is currently being addressed through biofortification breeding that relies on phenotypic selection. Gene-based markers linked to pro-vitamin A content variation are expected to increase the rate of genetic gain for this critical trait. We sequenced four candidate carotenoid genes from 167 cassava accessions representing the diversity of elite breeder lines from IITA. Total carotenoid content was determined using spectrophotometer and total β-carotene was quantified by high-performance liquid chromatography. Storage root yellowness due to carotenoid pigmentation was assessed. We carried out candidate gene association analysis that accounts for population structure and kinship using genome-wide single nucleotide polymorphisms (SNPs) generated through genotyping-by-sequencing. Significant SNPs were used to design competitive allele-specific PCR assays and validated on the larger population for potential use in marker-assisted selection breeding. Candidate gene sequencing of the genes β-carotene hydroxylase (crtRB), phytoene synthase (PSY2), lycopene epsilon cyclase (lcyE), and lycopene beta cyclase (lcyB) yielded a total of 37 SNPs. Total carotenoid content, total β-carotene, and color parameters were significantly associated with markers in the PSY2 gene. The SNPs from lcyE were significantly associated with color while those of lcyB and crtRB were not significantly associated with carotenoids or color parameters. These validated and breeder-friendly markers have potential to enhance the efficiency of selection for high β-carotene cassava, thus accelerating genetic gain.

Brood size manipulations reveal relationships among physiological performance, body condition and plumage colour in Northern Flicker Colaptes auratus nestlings

Visual signals of quality in offspring, such as plumage colour, should honestly advertise need and/or body condition, but links between nutritional status, physiological performance and the expression of colours are complex and poorly understood. We assess how food stress during rearing affected two physiological measures (T‐cell‐mediated immune function and corticosterone level in feathers: CORTf) and how these two variables were related to carotenoid and melanin coloration in Northern Flicker Colaptes auratus nestlings. We were also interested in how these two physiological measures were influenced by the sex of the nestling. We experimentally manipulated brood size to alter levels of food availability to nestlings during development. We measured carotenoid‐based colour (chroma and brightness) in wing feathers and the size of melanin spots on breast feathers. In agreement with our prediction, nestlings in the reduced brood treatment had better body condition and stronger immune responses than those in the control and brood enlargement treatments. This supports the hypothesis that immune responses are energetically costly. In contrast, CORTf was not related to nestling body condition or sex and was unaffected by brood size manipulation. Nestlings of both sexes with stronger T‐cell‐mediated immune responses had larger melanin spots but only males with higher immune responses also had brighter flight feathers. Feather brightness decreased with increasing CORTf levels. Our study is one of the few to examine the relationship between multiple physiological and plumage measures in nestlings and shows that plumage colour and immune function signalled body condition of nestlings, but that feather corticosterone levels did not.

High-density lipoprotein receptor SCARB1 is required for carotenoid coloration in birds

Yellow, orange, and red coloration is a fundamental aspect of avian diversity and serves as an important signal in mate choice and aggressive interactions. This coloration is often produced through the deposition of diet-derived carotenoid pigments, yet the mechanisms of carotenoid uptake and transport are not well-understood. The white recessive breed of the common canary (Serinus canaria), which carries an autosomal recessive mutation that renders its plumage pure white, provides a unique opportunity to investigate mechanisms of carotenoid coloration. We carried out detailed genomic and biochemical analyses comparing the white recessive with yellow and red breeds of canaries. Biochemical analysis revealed that carotenoids are absent or at very low concentrations in feathers and several tissues of white recessive canaries, consistent with a genetic defect in carotenoid uptake. Using a combination of genetic mapping approaches, we show that the white recessive allele is due to a splice donor site mutation in the scavenger receptor B1 (SCARB1; also known as SR-B1) gene. This mutation results in abnormal splicing, with the most abundant transcript lacking exon 4. Through functional assays, we further demonstrate that wild-type SCARB1 promotes cellular uptake of carotenoids but that this function is lost in the predominant mutant isoform in white recessive canaries. Our results indicate that SCARB1 is an essential mediator of the expression of carotenoid-based coloration in birds, and suggest a potential link between visual displays and lipid metabolism.

Impact of fresh fruit smoothie consumption on apparent health of Asian faces

Abstract Skin carotenoid coloration has been proposed as a valid cue to health in humans, reflecting fruit and vegetable intake, and enhancing apparent health. Supplementation with a carotenoid-rich fruit and vegetable smoothie affects skin color, but it is not known if this skin color change enhances healthy appearance. In three experiments, we examine the effects of skin color change induced by supplementation with a carotenoid-rich fruit smoothie (25mg carotenoids/d) on the apparent health of Malaysian Chinese faces. In experiment 1, observers were asked to identify the healthier looking of pairs of photographs of the same subject taken pre- and post-supplementation (or pre- and post-placebo), choosing the pre-supplementation (or pre-placebo) images. When confounding due to facial expression was eliminated in experiment 2, observers showed no preference for unmodified pre-supplementation photograph or the same image with skin color manipulated to simulate a level of smoothie-induced color change associated with 4weeks of supplementation. In experiment 3, observers manipulated the skin color of face photographs along the smoothie-induced color change axis to optimize healthy appearance. Observers chose to induce a color change approximately equivalent to one third of the change induced by daily consumption of our carotenoid rich smoothie. This suggests that the skin color change induced by the supplementation enhanced apparent facial health, however the dose and duration of the supplementation overshot the optimal healthy-looking color of Malaysian Chinese skin. This suggests that there is an optimal carotenoid color for healthy appearance, and that this optimal level may be constrained by preferences for averageness, by the association between very yellow skin and ill health, or by negative health impacts of very high doses of carotenoids.

Rapid expansion of pigmentation genes in penaeid shrimp with absolute preservation of function

Crustaceans form their distinct patterns and colours through the interaction of the carotenoid astaxanthin with a protein called crustacyanin (CRCN). Presently, the expression of just two CRCN genes is thought to provide the protein subunits that combine to form the crustacyanin complex and associated carotenoid colour change from red to blue. This study aimed to explore the genetic complexity underlying the production of pigmentation and camouflage in penaeid shrimp. We isolated 35 new CRCN genes from 12 species, and their sequence analysis indicated that this gene family has undergone significant expansion and diversification in this lineage. Despite this duplication and sequence divergence, the structure of the CRCN proteins and their functional role in shrimp colour production has been strictly conserved. Using CRCN isoforms from Penaeus monodon as an example, we showed that isoforms were differentially expressed, and that subtle phenotypes were produced by the specific downregulation of individual isoforms. These findings demonstrate that our knowledge of the molecular basis of pigmentation in shrimp was overly simplistic, and suggests that multiple copies of the CRCN genes within species may be advantageous for colour production. This result is of interest for the origin and evolution of pigmentation in crustaceans, and the mechanisms by which gene function is maintained, diversified or sub-functionalized.

Pretreatments for melon drying implementing ultrasound and vacuum

The aim of this work was to evaluate the use of ultrasound, osmotic dehydration and vacuum as a pretreatment on melon drying and product quality. The pretreatment consisted in four processing conditions, using vacuum and/or ultrasound and a control sample with no application of ultrasound and vacuum. Melon samples were immersed in a liquid medium (distilled water or sucrose solution) and pretreated for 10, 20 and 30 min. The drying process was conducted in a fixed bed dryer at 60 °C and air velocity of 2 m/s. The dried pretreated samples with ultrasound and with a combination of ultrasound and vacuum presented faster drying rates. Evaluation of the final product was performed by means of total carotenoid content, texture, color and sensorial test. Dried melon pretreated using ultrasound and vacuum combined obtained higher total carotenoids content, softer texture and total color difference similar to the untreated dried fruit. Sensory evaluation showed that this pretreated sample had good acceptance and no significant difference from the dried untreated melon. Therefore, the use of ultrasound or a combination of ultrasound and vacuum as a pretreatment could improve the efficiency of melon drying, being an alternative to traditional drying and suitable to an industrial context.

Foam mat drying of mango: Effect of processing parameters on the drying kinetic and product quality

ABSTRACTThis study investigated the foam mat drying process parameters (temperature and concentration of foaming agents, albumin, and an emulsifier blend) and evaluated their effects on drying kinetics, color, carotenoid retention, and solubility of the mango pulp powder. Fick’s model was able to represent the foam mat drying kinetics. The foaming agents and high temperatures enhanced the carotenoid retention. This was explained by the greater effective water diffusion coefficients that allowed obtaining products with low moisture contents and water activities in short processing times of up to 3 h, with high carotenoid retention and color maintenance.

Red Carotenoid Coloration in the Zebra Finch Is Controlled by a Cytochrome P450 Gene Cluster

Bright-red colors in vertebrates are commonly involved in sexual, social, and interspecific signaling [1-8] and are largely produced by ketocarotenoid pigments. In land birds, ketocarotenoids such as astaxanthin are usually metabolically derived via ketolation of dietary yellow carotenoids [9, 10]. However, the molecular basis of this gene-environment mechanism has remained obscure. Here we use the yellowbeak mutation in the zebra finch (Taeniopygia guttata) to investigate the genetic basis of red coloration. Wild-type ketocarotenoids were absent in the beak and tarsus of yellowbeak birds. The yellowbeak mutation mapped to chromosome 8, close to a cluster of cytochrome P450 loci (CYP2J2-like) that are candidates for carotenoid ketolases. The wild-type zebra finch genome was found to have three intact genes in thiscluster: CYP2J19A, CYP2J19B, and CYP2J40. In yellowbeak, there are multiple mutations: loss of acomplete CYP2J19 gene, a modified remaining CYP2J19 gene (CYP2J19(yb)), and a non-synonymous SNP in CYP2J40. In wild-type birds, CYP2J19 loci are expressed in ketocarotenoid-containing tissues: CYP2J19A only in the retina and CYP2J19B in the beak and tarsus and to a variable extent in the retina. In contrast, expression of CYP2J19(yb) is barely detectable in the beak of yellowbeak birds. CYP2J40 has broad tissue expression and shows no differences between wild-type and yellowbeak. Our results indicate that CYP2J19 genes are strong candidates for the carotenoid ketolase and imply that ketolation occurs in the integument in zebra finches. Since cytochrome P450 enzymes include key detoxification enzymes, our results raise the intriguing possibility that red coloration may be an honest signal of detoxification ability.

Expression levels of GSTA2 and APOD genes might be associated with carotenoid coloration in golden pheasant (Chrysolophus pictus) plumage.

Carotenoids, which generate yellow, orange, and red colors, are crucial pigments in avian plumage. Investigations into genes associated with carotenoidbased coloration in avian species are important; however, such research is difficult because carotenoids cannot be synthetized in vertebrates as they are only derived from dietary sources. Here, the golden pheasant (Chrysolophus pictus) was used as a model in analysis of candidate gene expression profiles implicated in carotenoid binding and deposition. Using mass and Raman spectrometry to confirm the presence of carotenoids in golden pheasant feathers, we found C40H54O and C40H56O2 in feathers with yellow to red colors, and in the rachis of iridescent feathers. The global gene expression profiles in golden pheasant skins were analyzed by RNA-seq and all six carotenoid binding candidate genes sequenced were studied by realtime PCR. StAR4, GSTA2, Scarb1, and APOD in feather follicles showed different expressions in red breast and orange nape feathers compared with that of iridescent mantle feathers. Further comparison of golden pheasant yellow rump and Lady Amherst's pheasant (Chrysolophus amherstiae) white nape feathers suggested that GSTA2 and APOD played a potential role in carotenoid-based coloration in golden pheasant.

The Importance of Carotenoid Dose in Supplementation Studies with Songbirds.

Carotenoid coloration is the one of the most frequently studied ornamental traits in animals. Many studies of carotenoid coloration test the associations between carotenoid coloration and measures of performance, such as immunocompetence and oxidative state, proceeding from the premise that carotenoids are limited resources. Such studies commonly involve supplementing the diets of captive birds with carotenoids. In many cases, however, the amount of carotenoid administered is poorly justified, and even supposedly carotenoid-limited diets may saturate birds' systems. To quantify the relationships among the amount of carotenoids administered in experiments, levels of circulating carotenoids, and quantities of carotenoids deposited into colored ornaments, we performed a meta-analysis of 15 published studies that supplemented carotenoids to one of seven songbird species. We used allometric scaling equations to estimate the per-gram carotenoid consumption of each study's subjects, and we used meta-regression to evaluate the effects of this carotenoid dose on differences in coloration and plasma carotenoid levels between supplemented and control groups of birds. After accounting for supplementation duration and species, we observed a significant positive correlation between carotenoid intake and response of plasma carotenoid level to supplementation. The presence of supplemental carotenoids also tended to increase the expression of ornamental coloration, but the magnitude of the carotenoid dose did not significantly affect how strongly coloration changed with supplementation. Further, coloration effect sizes had no significant relationship with plasma carotenoid effect sizes. We also found significant heterogeneity in responses among studies and species, and the parameters used to measure color significantly affected response to supplementation. Our results emphasize the importance of performing dosage trials to determine what supplementation levels provide limited versus surplus carotenoids and of measuring the natural level of carotenoid intake by the study species to validate the appropriateness of supplementation levels for a particular study species and experimental design.

Influence of dual-stage sugar substitution pretreatment on drying kinetics and quality parameters of mango

The aim of this work was to evaluate the use of the dual-stage (D3S) technique as a pretreatment on mango drying kinetics and on product quality. This pretreatment consisted in two stages, in which high-calorie sugars are partially removed from fruit samples in the first stage and, in the second stage, low-calorie sugar (Stevia-derived) is incorporated to the fruit to maintain its sweetness. The drying process was conducted in a fixed bed dryer at 60 °C and air velocity of 2 m/s. Experimental data were fitted successfully using the two-term exponential model. The dried pretreated samples presented faster drying rates. Evaluation of the final product was performed by means of total phenolic content, total carotenoid content, water activity, texture, color and sensorial test. Samples subjected D3S process had lower phenolic and carotenoid contents, reduced water activity, their texture was softer, and color difference was smaller compared to untreated samples. Sensory evaluation showed pretreated sample with good acceptance.

Condition‐dependent expression of carotenoid‐ and melanin‐based plumage colour of northern flicker nestlings revealed by manipulation of brood size

Carotenoid‐based colouration in feathers is widely accepted to be a reliable signal of the health of an individual, but the condition‐dependence of melanin‐based plumage ornaments has been highly debated. Using broods that were manipulated in size, we tested whether nutritional stress during rearing affected the carotenoid pigmentation in secondary feathers and the size, shape, and symmetry of melanin spots on breast plumage of northern flickerColaptes auratusnestlings. Two measures of carotenoid colour (chroma and brightness) of secondary flight feathers did not vary according to brood size treatment, but in a larger dataset from the population, carotenoid chroma was positively associated with nestling mass. Nestlings from experimentally enlarged broods had smaller melanin spots than those from reduced broods, which is some of the first experimental evidence that melanin ornament size in growing nestlings is condition‐dependent. However, the shape and symmetry of the melanin breast spots was not associated with nestling mass. Sexual dimorphism was apparent in both types of pigmentation and future studies should investigate whether there are any trade‐offs for nestlings between investing in carotenoid colouration and melanisation and whether trade‐offs differ between the sexes.

Influence of phosphorus management on melon (Cucumis melo L.) fruit quality.

At harvest time, melon quality is related to internal and external parameters, which are very important for consumer attractiveness and marketable yield. Several agronomic factors can affect the quality of melon fruits and among them mineral availability may play a significant role. Therefore the aim of the work was to investigate the effect of phosphorus fertigation on melon fruit (Cucumis melo L.) qualitative characteristics, such as fruit size and yield, pulp colour and firmness, aroma and taste, as well as the accumulation of bioactive antioxidant compounds, namely phenols and carotenoids, and their antiradical properties. Results allowed us to extrapolate the optimal P doses to be used for melon fertigation, to achieve high yield and fruit quality characteristics. Modelling the optimal P dose allowed us to maximize yield and resulted in around 257 kg P2 O5 ha(-1) , even if the quality indices relating to carotenoid content, texture and colour of the melon flesh were not significantly different between samples fertigated with the two highest levels tested. It can be assumed that the level of 200 kg P2 O5 ha(-1) would be a good compromise between optimization of agronomic performance and melon fruit quality. © 2015 Society of Chemical Industry.

Plumage coloration, body condition and immunological status in Yellow-billed Cardinals (Paroaria capitata)

Plumage coloration deriving from carotenoid and melanin pigments can be a quality signal in birds, and can be under conspecific inspection in social interactions. For example, parasite load and immune system status can be inferred through plumage color intensity, and can influence the choice of sexual partners. Here, we evaluated two plumage ornaments in the Yellow-billed Cardinal [Paroaria capitata (d’Orbigny & Lafresnaye 1837)]: the carotenoid-based coloration of the cap and the melanin-based coloration of the bib. We evaluated whether these ornaments were related to blood parasite burden, immunological status and body condition, and whether they could reveal individual sex and age. Cardinals were mist-netted in a Brazilian wetland, and 12 individuals were infected with malaria parasites. Both carotenoid and melanin colorations were related to age, but only carotenoids reflected immunological status. Adult cardinals presented redder caps and darker bibs in comparison to juveniles, and redder caps were associated with low values of heterophil to lymphocyte ratio (H/L, indicating lower stress level). Plumage coloration did not indicate individual sex or parasite infection. Taken together, these results demonstrated that both melanin- and carotenoid-based coloration in cardinals can potentially reflect significant information for social interactions, such as individual age and experience, but apparently only carotenoid coloration is condition-dependent and could reliably indicate quality.

Tradeoff between robustness and elaboration in carotenoid networks produces cycles of avian color diversification.

BackgroundResolution of the link between micro- and macroevolution calls for comparing both processes on the same deterministic landscape, such as genomic, metabolic or fitness networks. We apply this perspective to the evolution of carotenoid pigmentation that produces spectacular diversity in avian colors and show that basic structural properties of the underlying carotenoid metabolic network are reflected in global patterns of elaboration and diversification in color displays. Birds color themselves by consuming and metabolizing several dietary carotenoids from the environment. Such fundamental dependency on the most upstream external compounds should intrinsically constrain sustained evolutionary elongation of multi-step metabolic pathways needed for color elaboration unless the metabolic network gains robustness – the ability to synthesize the same carotenoid from an additional dietary starting point.ResultsWe found that gains and losses of metabolic robustness were associated with evolutionary cycles of elaboration and stasis in expressed carotenoids in birds. Lack of metabolic robustness constrained lineage’s metabolic explorations to the immediate biochemical vicinity of their ecologically distinct dietary carotenoids, whereas gains of robustness repeatedly resulted in sustained elongation of metabolic pathways on evolutionary time scales and corresponding color elaboration.ConclusionsThe structural link between length and robustness in metabolic pathways may explain periodic convergence of phylogenetically distant and ecologically distinct species in expressed carotenoid pigmentation; account for stasis in carotenoid colors in some ecological lineages; and show how the connectivity of the underlying metabolic network provides a mechanistic link between microevolutionary elaboration and macroevolutionary diversification.ReviewersThis article was reviewed by Junhyong Kim, Eugene Koonin, and Fyodor Kondrashov. For complete reports, see the Reviewers’ reports section.Electronic supplementary materialThe online version of this article (doi:10.1186/s13062-015-0073-6) contains supplementary material, which is available to authorized users.

Process optimization based on carrot powder color characteristics

The carotenoid content indicates the processing quality of carrot powder. The carotenoid content of carrot powder was analyzed using digital image processing technology and color analysis technology, and an estimation model between the carotenoid content and color characteristics was established. The carrot was dried using different drying methods. The verification test result shows that model fitting is prominent and the test error is small and promptly improves the reference of testing for the carotenoid content of carrot powder. The processing parameters of the carrot powder with the highest carotenoid content are as follows: the carrot was frozen and thawed using the freeze drying method; the powder particle size is 80–120 mesh.