Flesh Pigmentation Research Articles

Effect of natural carotenoids obtained from Haematococcus pluvialis, Paracoccus carotinifaciens, and Phaffia rhodozyma on flesh pigmentation and related biochemical mechanisms in Atlantic salmon (Salmo salar L.)

The present study highlights the efficiency of natural carotenoid sources (Haematococcus pluvialis, Phaffia rhodozyma, and Paracoccus carotinifaciens) in terms of Atlantic salmon pigmentation, lipid profile, oxidation status (glutathione (GSH)/glutathione disulfide (GSSG)) ratio, and genomic stress markers (nrf2.1, keap1b1, hsp70, and h2q8 genes) during an 88-day feeding trial. As controls, fish fed synthetic astaxanthin was used. Four experimental diets with equal nutritional composition, except for the pigment source, were tested in an experimental design of 12 tanks and 372 fish (n = 3 × 31 per feed, start weight of 149 ± 27.5 g).Astaxanthin from H. pluvialis, P. rhodozyma, and P. carotinifaciens were found to be as efficient as synthetic astaxanthin in terms of visual perception, oxidation status and lipid peroxidation as there were no significant differences (p > 0.05) in a* value, GSH/GSSG ratio, or lipid profile between the different groups. Additionally, there were no significant differences in the gene expression of nrf2.1, keap1b1, or hsp70 in the NQC or the PC. Fish fed P. rhodozyma showed the most favorable results as it had the numerically highest a* and C* values and the lowest L* value. Moreover, no significant difference in total muscle astaxanthin concentration was observed between the fish fed P. rhodozyma and those fed synthetic astaxanthin. However, the fish fed synthetic astaxanthin had a significantly higher concentration of total flesh astaxanthin than those fed H. pluvialis and P. carotinifaciens.The results conclude that naturally produced astaxanthin has a significant potential in Atlantic salmon pigmentation. However, further research on slaughter-ready salmon is essential to prove the concept.

A comparative analysis of the volatile profiles in the pulp of red-fleshed and standard orange varieties during fruit maturation

Kirkwood Navel and Ruby Valencia red-fleshed sweet oranges accumulate high concentrations of the carotenes phytoene, phytofluene and lycopene in the pulp. In order to gain insight into the parameters that influence fruit quality in these varieties, a comparative analysis of volatile organic compounds (VOCs) in the pulp of Kirkwood Navel and Ruby Valencia red-fleshed sweet oranges and their standard blond counterparts, Navel and Valencia, was performed during fruit development and ripening. A total of 95 VOCs were identified by HS-SPME/GC–MS during the ripening process. The observed differences in VOCs between red-fleshed and blond oranges were more closely related to the fruit ripening stage than to the genotype. However, two distinctive common features were identified in both red-fleshed oranges compared to their respective standard varieties. These were lower levels of sesquiterpenes and higher levels of the norisoprenoids 6-methyl-5-hepten-2-one and geranylacetone. These findings indicate that altered carotenoid metabolism in red-fleshed oranges not only affects flesh pigmentation but also leads to changes in specific VOCs that may influence flavor perception.

Transcriptomic and Metabolic Analysis Reveals Genes and Pathways Associated with Flesh Pigmentation in Potato (Solanum tuberosum) Tubers.

Anthocyanins, flavonoid pigments, are responsible for the purple and red hues in potato tubers. This study analyzed tubers from four potato cultivars-red RR, purple HJG, yellow QS9, and white JZS8-to elucidate the genetic mechanisms underlying tuber pigmentation. Our transcriptomic analysis identified over 2400 differentially expressed genes between these varieties. Notably, genes within the flavonoid biosynthesis pathway were enriched in HJG and RR compared to the non-pigmented JZS8, correlating with their higher levels of anthocyanin precursors and related substances. Hierarchical clustering revealed inverse expression patterns for the key genes involved in anthocyanin metabolism between pigmented and non-pigmented varieties. Among these, several MYB transcription factors displayed strong co-expression with anthocyanin biosynthetic genes, suggesting a regulatory role. Specifically, the expression of 16 MYB genes was validated using qRT-PCR to be markedly higher in pigmented HJG and RR versus JZS8, suggesting that these MYB genes might be involved in tuber pigmentation. This study comprehensively analyzed the transcriptome of diverse potato cultivars, highlighting specific genes and metabolic pathways involved in tuber pigmentation. These findings provide potential molecular targets for breeding programs focused on enhancing tuber color.

EjWRKY6 Is Involved in the ABA-Induced Carotenoid Biosynthesis in Loquat Fruit during Ripening.

The yellow-fleshed loquat is abundant in carotenoids, which determine the fruit's color, provide vitamin A, and offer anti-inflammatory and anti-cancer health benefits. In this research, the impact of abscisic acid (ABA), a plant hormone, on carotenoid metabolism and flesh pigmentation in ripening loquat fruits was determined. Results revealed that ABA treatment enhanced the overall content of carotenoids in loquat fruit, including major components like β-cryptoxanthin, lutein, and β-carotene, linked to the upregulation of most genes in the carotenoid biosynthesis pathway. Furthermore, a transcription factor, EjWRKY6, whose expression was induced by ABA, was identified and was thought to play a role in ABA-induced carotenoid acceleration. Transient overexpression of EjWRKY6 in Nicotiana benthamiana and stable genetic transformation in Nicotiana tabacum with EjWRKY6 indicated that both carotenoid production and genes related to carotenoid biosynthesis could be upregulated in transgenic plants. A dual-luciferase assay proposed a probable transcriptional control between EjWRKY6 and promoters of genes associated with carotenoid production. To sum up, pre-harvest ABA application could lead to carotenoid biosynthesis in loquat fruit through the EjWRKY6-induced carotenoid biosynthesis pathway.

Northern shrimp (Pandalus borealis) protein hydrolyzate and oil promote flesh pigmentation and growth in post-smolt Atlantic salmon (Salmo salar)

ABSTRACT This study investigated the use of alternative ingredients obtained from Pandalus borealis by-products on flesh pigmentation and growth in post-smolt Salmo salar (initial weight of ~ 300 g). Four experimental diets were fed to fish in triplicate tanks for 16 weeks: a control diet and three other diets containing either synthetic astaxanthin, shrimp hydrolyzate, or shrimp oil. Fish that were fed the shrimp hydrolyzate diet exhibited higher red hue (based on L*a*b* data) when compared to fish fed the two other pigmented diets and had higher final weight. In addition, shrimp oil was found to be as efficient as artificial astaxanthin to increase the intensity of flesh pigmentation in Atlantic salmon. The shrimp hydrolyzate tested in our study provides an excellent source of astaxanthin and protein for Atlantic salmon. Likewise, shrimp oil could also constitute a natural source of astaxanthin and oil to this species.

Improved Flesh Pigmentation of Rainbow Trout (Oncorhynchus mykiss) by Feeding Z-Isomer-Rich Astaxanthin Derived from Natural Origin.

The use of Paracoccus carotinifaciens-derived natural astaxanthin as an alternative to synthetic astaxanthin has attracted considerable attention from the aquaculture industry. Furthermore, to enhance the bioavailability of astaxanthin, its "Z-isomerization" has been actively studied in recent years. This study investigated the effects of feeding a diet containing astaxanthin rich in the all-E- or Z-isomers derived from P. carotinifaciens on the pigmentation and astaxanthin concentration in rainbow trout (Oncorhynchus mykiss) flesh. Z-Isomer-rich astaxanthin was prepared from the P. carotinifaciens-derived all-E-isomer by thermal treatment in fish oil, and the prepared all-E-isomer-rich astaxanthin diet (E-AST-D; total Z-isomerratio = 9.1%) and Z-isomer-rich astaxanthin diet (Z-AST-D; total Z-isomer ratio of astaxanthin = 56.6%) were fed to rainbow trout for 8 weeks. The feeding of Z-AST-D resulted in greater pigmentation and astaxanthin accumulation efficiency in the flesh than those fed E-AST-D. Specifically, when E-AST-D was fed to rainbow trout, the SalmoFan score and astaxanthin concentration of the flesh were 22.1±1.4 and 1.36±0.71 μg/g wet weight, respectively, whereas when Z-AST-D was fed, their values were 26.0±2.5 and 5.33±1.82 μg/g wet weight, respectively. These results suggest that P. carotinifaciens-derived astaxanthin Z- isomers prepared by thermal isomerization are more bioavailable to rainbow trout than the all-E-isomer.

SmuMYB113 is the determinant of fruit color in pepino (Solanum muricatum).

Pepino (Solanum muricatum) is an herbaceous crop phylogenetically related to tomato and potato. Pepino fruit vary in color, size and shape, and are eaten fresh. In this study, we use pepino as a fruit model to understand the transcriptional regulatory mechanisms controlling fruit quality. To identify the key genes involved in anthocyanin biosynthesis in pepino, two genotypes were studied that contrasted in foliar and fruit pigmentation. Anthocyanin profiles were analyzed, as well as the expression of genes that encode enzymes for anthocyanin biosynthesis and transcriptional regulators using both RNA-seq and quantitative PCR. The differential expression of the transcription factor genes R2R3 MYB SmuMYB113 and R3MYB SmuATV suggested their association with purple skin and foliage phenotype. Functional analysis of these genes in both tobacco and pepino showed that SmuMYB113 activates anthocyanins, while SmuATV suppresses anthocyanin accumulation. However, despite elevated expression in all tissues, SmuMYB113 does not significantly elevate flesh pigmentation, suggesting a strong repressive background in fruit flesh tissue. These results will aid understanding of the differential regulation controlling fruit quality aspects between skin and flesh in other fruiting species.

Citrus Fruit Pigments

Citrus fruits enjoy popularity among consumers due to their enjoyable flavor, health-beneficial properties, and nutritional value. The peel and flesh pigmentation of different citrus species and cultivars ranges from green, to yellow, orange, pink and red. Pigmentation is influenced by genetics, environmental conditions, and tree management. Mature fruit of edible citrus are diverse in size, flavor, and peel and flesh color. The external color of citrus fruits is one of their most important quality characteristics, but the internal pigments also play a significant role in determining their health benefits. The edible part of citrus fruits, including sweet orange, mandarin, pummelo, grapefruit, lime, and lemon, has distinct attributes and pigments.

Multiomics Analysis Reveals the Chemical and Genetic Bases of Pigmented Potato Tuber.

Anthocyanins and carotenoids determine the diversity of potato tuber flesh pigmentation; here, the underlying chemical and genetic bases were elucidated by multiomics analyses. A total of 31 anthocyanins and 30 carotenoids were quantified in five differently pigmented tubers. Cyanidin and pelargonidin derivatives determined the redness, while malvidin, petunidin, and delphinidin derivatives contributed to purpleness. Violaxanthin derivatives determined the light-yellow color, while zeaxanthin and antheraxanthin derivatives further enhanced the deep-yellow deposition. Integrated transcriptome and proteome analyses identified that F3'5'H highly enhanced anthocyanin biosynthesis in purple flesh and was responsible for metabolic divergence between red and purple samples. BCH2 significantly enhanced carotenoid biosynthesis in yellow samples and along with ZEP, NCED1, and CCD1 genes determined metabolic divergence between light and deep-yellow samples. The weighted correlation network analysis constructed a regulatory network revealing the central role of AN1 in regulating anthocyanin biosynthesis, and 10 new transcription factors related to anthocyanin and carotenoid metabolism regulation were identified. Our findings provide targeted genes controlling tuber pigmentation, which will be meaningful for the genetic manipulation of tuber quality improvement.

Analysis of carotenoids and fatty acid compositions in Atlantic salmon exposed to elevated temperatures and displaying flesh color loss.

Tasmanian-farmed Atlantic salmon populations exhibit starvation followed by a reduced growth rate alongside reduced flesh pigmentation in response to elevated summer temperatures, which at times can exceed their optimum threshold. Here we investigated fatty acids and carotenoids of Atlantic salmon displaying three different flesh color phenotypes, using metabolomic and chemical analyses of lipids and pigments in six key tissues. Astaxanthin is mainly responsible for flesh pigmentation, while canthaxanthin is associated with carotenoid catabolism in the liver, as our findings indicate. Reduced flesh pigmentation correlated with lower levels of carotenoids across all tested tissues and clear evidence of a correlation between carotenoid and fatty acid levels in all detected fatty acid classes was observed. The reduced growth performance and flesh pigmentation are most likely due to the impact of varying levels of starvation on fatty acids and carotenoid profiles supporting the link between carotenoids and fatty acid metabolic processes.

Comparison on inclusion of potent and expired Astaxanthin in the diet of ANH7 African catfish Clarias gariepinus fingerlings for skin and flesh pigmentation

Background and Objective: The aim of this study seeks to Compare the effects of Inclusion levels of Potent and Expired Astaxanthin in the Diet of African catfish Clarias gariepinus Fingerlings for Skin and Flesh Pigmentation. Materials and Methods: A 120 fingerlings Clarias gariepinus was used which was procured from a reputable farm in Jos, Plateau State, Nigeria. They were then taken to the Hydrobiology and Fisheries Laboratory of the University of Jos, Nigeria and allowed to acclimatize for three weeks before the feeding started. The experiment involved the use of 19 fibre glass tanks having average capacity of 95 litres. It was run under the flow-through system at 100 ml/min in order to avoid pollution. Results: After a feeding period of eight weeks, increasing the level of astaxanthin (potent and expired) in the feed of Clarias gariepinus fingerlings from 100 (T1) to 150 (T2) to 200g/kg (T3), the concentration of carotene in the skin increased significantly (p < 0.05) between the treatments except for the control. The effect of pigmentation was given in the skin and flesh of Clarias gariepinus fingerlings fed both potent and expired astaxanthin, except that, the potent astaxanthin gave higher effect of pigmentation on both skin and flesh than the expired astaxanthin. Conclusion: It was however, found that, the concentration of astaxanthin in the skin was higher than that in the flesh under every treatment for both potent and expired astaxanthin.

Histological and transcriptomic analysis of muscular atrophy associated with depleted flesh pigmentation in Atlantic salmon (Salmo salar) exposed to elevated seawater temperatures

Tasmania is experiencing increasing seawater temperatures during the summer period which often leads to thermal stress-induced starvation events in farmed Atlantic salmon, with consequent flesh pigment depletion. Our previous transcriptomic studies found a link between flesh pigmentation and the expression of genes regulating lipid metabolism accompanied by feeding behavior in the hindgut. However, the impact of prolonged exposure to elevated water temperature on muscle structural integrity and molecular mechanisms in muscle underlying pigment variation has not been elucidated to date. In this study, we investigated the effect of prolonged exposure to elevated water temperature on the farmed salmon flesh pigmentation and structural integrity, using muscle histological and transcriptomic analysis. On April 2019, after the end of the summer, two muscle regions of the fish fillet, front dorsal and back central (usually the most and least affected by depletion, respectively), were sampled from fifteen fish (weighing approximately 2 kg and belonging to the same commercial population split in two cages). The fish represented three flesh color intensity groups (n = 5 fish per group) categorized according to general level of pigmentation and presence of banding (i.e. difference in color between the two regions of interest) as follows: high red color-no banding (HN), high red color-banded (HB) and Pale fish. Histological analysis showed a distinction between the flesh color intensity phenotypes in both muscle regions. Muscle fibers in the HB fish were partly degraded, while they were atrophied and smaller in size in Pale fish compared to HN fish. In the Pale fish, interstitial spaces between muscle fibers were also enlarged. Transcriptomic analysis showed that in the front dorsal region of the HN fish, genes encoding collagens, calcium ion binding and metabolic processes were upregulated while genes related to lipid and fatty acid metabolism were downregulated when compared to HB fish. When comparing the back central region of the three phenotypes, actin alpha skeletal muscle and myosin genes were upregulated in the HN and HB fish, while tropomyosin genes were upregulated in the Pale fish. Also, genes encoding heat shock proteins were upregulated in the HN fish, while genes involving lipid metabolism and proteolysis were upregulated in the Pale fish. Starvation, likely caused by thermal stress during prolonged periods of elevated summer water temperatures, negatively affects energy metabolism to different extents, leading to localized or almost complete flesh color depletion in farmed Atlantic salmon. Based on our results, we conclude that thermal stress is responsible not only for flesh discoloration but also for loss of muscle integrity, which likely plays a key role in pigment depletion.

Integrative analysis of metabolome and transcriptome reveals a dynamic regulatory network of potato tuber pigmentation

Potatoes consist of flavonoids that provide health benefits for human consumers. To learn more about how potato tuber flavonoid accumulation and flesh pigmentation are controlled, we analyzed the transcriptomic and metabolomic profile of potato tubers from three colored potato clones at three developmental phases using an integrated approach. From the 72 flavonoids identified in pigmented flesh, differential abundance was noted for anthocyanins, flavonols, and flavones. Weighted gene co-expression network analysis further allowed modules and candidate genes that positively or negatively regulate flavonoid biosynthesis to be identified. Furthermore, an R2R3-MYB repressor StMYB3 and an R3-MYB repressor StMYBATV involved in the modulation of anthocyanin biosynthesis during tuber development were identified. Both StMYB3 and StMYBATV could interact with the cofactor StbHLH1 and repress anthocyanin biosynthesis. Our results indicate a feedback regulatory mechanism of a coordinated MYB activator-repressor network on fine-tuning of potato tuber pigmentation during tuber development.

Molecular Mechanism Involved in Carotenoid Metabolism in Post-Smolt Atlantic Salmon: Astaxanthin Metabolism During Flesh Pigmentation and Its Antioxidant Properties

A better understanding of carotenoid dynamics (transport, absorption, metabolism, and deposition) is essential to develop a better strategy to improve astaxanthin (Ax) retention in muscle of Atlantic salmon. To achieve that, a comparison of post-smolt salmon with (+ Ax) or without (- Ax) dietary Ax supplementation was established based on a transcriptomic approach targeting pyloric, hepatic, and muscular tissues. Results in post-smolts showed that the pyloric caeca transcriptome is more sensitive to dietary Ax supplementation compared to the other tissues. Key genes sensitive to Ax supplementation could be identified, such as cd36 in pylorus, agr2 in liver, or fbp1 in muscle. The most modulated genes in pylorus were related to absorption but also metabolism of Ax. Additionally, genes linked to upstream regulation of the ferroptosis pathway were significantly modulated in liver, evoking the involvement of Ax as an antioxidant in this process. Finally, the muscle seemed to be less impacted by dietary Ax supplementation, except for genes related to actin remodelling and glucose homeostasis. In conclusion, the transcriptome data generated from this study showed that Ax dynamics in Atlantic salmon is characterized by a high metabolism during absorption at pyloric caeca level. In liver, a link with a potential of ferroptosis process appears likely via cellular lipid peroxidation. Our data provide insights into a better understanding of molecular mechanisms involved in dietary Ax supplementation, as well as its beneficial effects in preventing oxidative stress and related inflammation in muscle.

Deploying new generation sequencing for the study of flesh color depletion in Atlantic Salmon (Salmo salar)

BackgroundThe flesh pigmentation of farmed Atlantic salmon is formed by accumulation of carotenoids derived from commercial diets. In the salmon gastrointestinal system, the hindgut is considered critical in the processes of carotenoids uptake and metabolism. In Tasmania, flesh color depletion can noticeably affect farmed Atlantic salmon at different levels of severity following extremely hot summers. In this study, RNA sequencing (RNA-Seq) was performed to investigate the reduction in flesh pigmentation. Library preparation is a key step that significantly impacts the effectiveness of RNA sequencing (RNA-Seq) experiments. Besides the commonly used whole transcript RNA-Seq method, the 3’ mRNA-Seq method is being applied widely, owing to its reduced cost, enabling more repeats to be sequenced at the expense of lower resolution. Therefore, the output of the Illumina TruSeq kit (whole transcript RNA-Seq) and the Lexogen QuantSeq kit (3’ mRNA-Seq) was analyzed to identify genes in the Atlantic salmon hindgut that are differentially expressed (DEGs) between two flesh color phenotypes.ResultsIn both methods, DEGs between the two color phenotypes were associated with metal ion transport, oxidation-reduction processes, and immune responses. We also found DEGs related to lipid metabolism in the QuantSeq method. In the TruSeq method, a missense mutation was detected in DEGs in different flesh color traits. The number of DEGs found in the TruSeq libraries was much higher than the QuantSeq; however, the trend of DEGs in both library methods was similar and validated by qPCR.ConclusionsFlesh coloration in Atlantic salmon is related to lipid metabolism in which apolipoproteins, serum albumin and fatty acid-binding protein genes are hypothesized to be linked to the absorption, transport and deposition of carotenoids. Our findings suggest that Grp could inhibit the feeding behavior of low color-banded fish, resulting in the dietary carotenoid shortage. Several SNPs in genes involving in carotenoid-binding cholesterol and oxidative stress were detected in both flesh color phenotypes. Regarding the choice of the library preparation method, the selection criteria depend on the research design and purpose. The 3’ mRNA-Seq method is ideal for targeted identification of highly expressed genes, while the whole RNA-Seq method is recommended for identification of unknown genes, enabling the identification of splice variants and trait-associated SNPs, as we have found for duox2 and duoxa1.

Determination of Biochemical Composition in Peach (Prunus persica L. Batsch) Accessions Characterized by Different Flesh Color and Textural Typologies.

The rising interest in beneficial health properties of polyphenol compounds in fruit initiated this investigation about biochemical composition in peach mesocarp/exocarp. Biochemical evaluation of phenolic compounds and ascorbic acid were quantified through high-performance liquid chromatography (HPLC) in relation to three flesh colors (white, yellow and red) and four flesh typologies (melting, non-melting, slow softening and stony hard) within six commercial cultivars and eight breeding selections of peach/nectarine in 2007. While in 2008, quality and sensorial analyses were conducted on only three commercial cultivars (‘Big Top’, ‘Springcrest’ and ‘Ghiaccio 1’). The red flesh selection demonstrated the highest levels of phenolic compounds (in mesocarp/exocarp) and ascorbic acid. Total phenolic concentration was approximately three-fold higher in the exocarp than the mesocarp across all accessions. Breeding selections generally reported higher levels of phenolics than commercial cultivars. Flesh textural typologies justified firmness differences at harvest, but minimally addressed variations in quality and phenolic compounds. Flesh pigmentation explained variation in the biochemical composition, with the red flesh accession characterized by an abundancy of phenolic compounds and a high potential for elevated antioxidant activity. Sensorial analyses ranked the cultivar with high soluble solids concentration:titratable acidity (SSC:TA) and reduced firmness the highest overall. Red flesh is a highly desirable trait for breeding programs aiming to improve consumption of peaches selected for nutraceutical properties.

Atlantic Salmon (Salmo salar L., 1758) Gut Microbiota Profile Correlates with Flesh Pigmentation: Cause or Effect?

In Tasmania (Australia), during the marine phase, it has been observed that flesh pigmentation significantly drops in summer, possibly due to high water temperatures (> 20°C). Although this deleterious effect of summer temperatures has been ascertained, there is a lack of knowledge of the actual mechanisms behind the impaired uptake and/or loss of pigments in Atlantic salmon in a challenging environment. Since the microbial community in the fish intestine significantly changes in relation to the variations of water temperature, this study was conducted to assess how the gut microbiota profile also correlates with the flesh color during temperature fluctuation. We sampled 68 fish at three time points covering the end of summer to winter at a marine farm in Tasmania, Australia. Flesh color was examined in two ways: the average color throughout and the evenness of the color between different areas of the fillet. Using 16S rRNA sequencing of the v3-v4 region, we determined that water temperature corresponded to changes in the gut microbiome both with alpha diversity (Kruskal-Wallis tests P = 0.05) and beta diversity indices (PERMANOVA P = 0.001). Also, there was a significant correlation between the microbiota and the color of the fillet (PERMANOVA P = 0.016). There was a high abundance of Pseudoalteromonadaceae, Enterobacteriaceae, Microbacteriaceae, and Vibrionaceae in the pale individuals. Conversely, carotenoid-synthesizing bacteria families (Bacillaceae, Mycoplasmataceae, Pseudomonas, Phyllobacteriaceae, and Comamonadaceae) were found in higher abundance in individuals with darker flesh color.

Effect of Black Mulberry (Morus nigra) Powder on Growth Performance, Biochemical Parameters, Blood Carotenoid Concentration, and Fillet Color of Rainbow Trout

Abstract The degree of flesh pigmentation is one of the most important quality criteria dictating the fish market value. It is well known that fish, like other animals, cannot synthesize their own coloring pigments de novo, and must obtain these pigments from their diet. In this study, four levels of black mulberry (Morus nigra) juice powder (BMP) as a natural pigment source were incorporated into a basal diet at concentrations of 0, 0.25, 0.5, and 0.75% and fed to rainbow trout weighing 100±5 g for 8 weeks in triplicate. At the end of the feeding trial, the effect of BMP on growth performance, blood biochemical parameters and fillet color was examined. Fish fed BMP showed significant enhancements in weight gain (WG), specific growth (SGR), food conversion ratio (FCR), and survival rates (SR) (P<0.05). SGR, WG and SR values were increased significantly following dietary supplementation with BMP in a dose dependent manner with the highest values in fish fed 0.75%, while the FCR was decreased (P<0.05). Body crude protein, lipid, and moisture contents were increased significantly in fish fed BMP (P<0.05). Dietary BMP has significantly decreased the levels of blood ALT, AST, and glucose (P>0.05). While the blood carotenoid concentration was increased in fish fed 0.5% BMP compared to other treated groups. Fish fed BMP showed increased fillet yellowness (b*) and redness (a*), while the fillet lightness (L*) was decreased when compared to the control (P<0.05). In conclusion, diets supplemented with BMP increased the growth performance, muscle pigmentation, and health status of rainbow trout.

Carbon starvation reduces carbohydrate and anthocyanin accumulation in red-fleshed fruit via trehalose 6-phosphate and MYB27.

Kiwifruit (Actinidia spp.) is a recently domesticated fruit crop with several novel-coloured cultivars being developed. Achieving uniform fruit flesh pigmentation in red genotypes is challenging. To investigate the cause of colour variation between fruits, we focused on a red-fleshed Actinidia chinensis var. chinensis genotype. It was hypothesized that carbohydrate supply could be responsible for this variation. Early in fruit development, we imposed high or low (carbon starvation) carbohydrate supplies treatments; carbohydrate import or redistribution was controlled by applying a girdle at the shoot base. Carbon starvation affected fruit development as well as anthocyanin and carbohydrate metabolite concentrations, including the signalling molecule trehalose 6-phosphate. RNA-Seq analysis showed down-regulation of both gene-encoding enzymes in the anthocyanin and carbohydrate biosynthetic pathways. The catalytic trehalose 6-phosphate synthase gene TPS1.1a was down-regulated, whereas putative regulatory TPS7 and TPS11 were strongly up-regulated. Unexpectedly, under carbon starvation MYB10, the anthocyanin pathway regulatory activator was slightly up-regulated, whereas MYB27 was also up-regulated and acts as a repressor. To link these two metabolic pathways, we propose a model where trehalose 6-phosphate and the active repressor MYB27 are involved in sensing the carbon starvation status. This signals the plant to save resources and reduce the production of anthocyanin in fruits.

Transcriptomic and metabolomic profiling provide novel insights into fruit development and flesh coloration in Prunus mira Koehne, a special wild peach species

BackgroundFlesh color is one of the most important traits for the commercial value of peach fruit. To unravel the underlying regulatory network in Prunus mira, we performed an integrated analysis of the transcriptome and metabolome of 3 fruit types with various flesh pigmentations (milk-white, yellow and blood) at 3 developmental stages (pit-hardening, cell enlargement and fruit ripening).ResultsTranscriptome analysis showed that an intense transcriptional adjustment is required for the transition from the pit-hardening to the cell enlargement stage. In contrast, few genes were differentially expressed (DEGs) from the cell enlargement to the fruit ripening stage and importantly, the 3 fruits displayed diverse transcriptional activities, indicating that difference in fruit flesh pigmentations mainly occurred during the ripening stage. We further investigated the DEGs between pairs of fruit types during the ripening stage and identified 563 DEGs representing the ‘core transcriptome’ associated with major differentiations between the 3 fruit types, including flesh pigmentation. Meanwhile, we analyzed the metabolome, particularly, at the ripening stage and uncovered 40 differential metabolites (‘core metabolome’) between the 3 fruit types including 5 anthocyanins, which may be the key molecules associated with flesh coloration. Finally, we constructed the regulatory network depicting the interactions between anthocyanins and important transcripts involved in fruit flesh coloration.ConclusionsThe major metabolites and transcripts involved in fruit flesh coloration in P. mira were unraveled in this study providing valuable information which will undoubtedly assist in breeding towards improved fruit quality in peach.