Regulation Of Carotenoid Accumulation Research Articles

Involvement of Transcription Factors and Regulatory Proteins in the Regulation of Carotenoid Accumulation in Plants and Algae.

Carotenoids are essential for photosynthesis and photoprotection in photosynthetic organisms, which are widely used in food coloring, feed additives, nutraceuticals, cosmetics, and pharmaceuticals. Carotenoid biofortification in crop plants or algae has been considered as a sustainable strategy to improve human nutrition and health. However, the regulatory mechanisms of carotenoid accumulation are still not systematic and particularly scarce in algae. This article focuses on the regulatory mechanisms of carotenoid accumulation in plants and algae through regulatory factors (transcription factors and regulatory proteins), demonstrating the complexity of homeostasis regulation of carotenoids, mainly including transcriptional regulation as the primary mechanism, subsequent post-translational regulation, and cross-linking with other metabolic processes. Different organs of plants and different plant/algal species usually have specific regulatory mechanisms for the biosynthesis, storage, and degradation of carotenoids in response to the environmental and developmental signals. In plants and algae, regulators such as MYB, bHLH, MADS, bZIP, AP2/ERF, WRKY, and orange proteins can be involved in the regulation of carotenoid metabolism. And many more regulators, regulatory networks, and mechanisms need to be explored. Our paper will provide a basis for multitarget or multipathway engineering for carotenoid biofortification in plants and algae.

Ethylene promotes carotenoid accumulation in peach pulp after harvest

The effects of exogenous ethylene and ethylene antagonist (1-methylcyclopropene, 1-MCP) on carotenoid metabolism in the flesh of peach fruit after harvest were investigated. The results revealed that ethylene treatment increased the content of total carotenoids together with the major carotenoid compositions including lutein, β-carotene, β-cryptoxanthin and zeaxanthin and thus promoted fruit coloration during storage of peach fruit, whereas 1-MCP treatment had an opposite effect. Moreover, ethylene also accelerated endogenous ethylene production rate and fruit softening in peaches during storage, which was inhibited by 1-MCP treatment. Gene expression analysis showed that the transcript levels of three carotenoid synthetic genes (PpPSY, PpZDS and PpCHYB) and two transcription factors (PpERF2 and PpNAC71) in peach pulp were increased by ethylene treatment and decreased by 1-MCP treatment as compared with the controls, while the expression of PpMADS1 transcription factor exhibited opposite responses to these two treatments. These results suggest ethylene is involved in the regulation of carotenoid accumulation and fruit coloration in postharvest peaches.

Temperature regulation of carotenoid accumulation in the petals of sweet osmanthus via modulating expression of carotenoid biosynthesis and degradation genes

BackgroundTemperature is involved in the regulation of carotenoid accumulation in many plants. The floral color of sweet osmanthus (Osmanthus fragrans Lour.) which is mainly contributed by carotenoid content, is affected by temperature in autumn. However, the mechanism remains unknown. Here, to reveal how temperature regulates the floral color of sweet osmanthus, potted sweet osmanthus ‘Jinqiu Gui’ were treated by different temperatures (15 °C, 19 °C or 32 °C). The floral color, carotenoid content, and the expression level of carotenoid-related genes in petals of sweet osmanthus ‘Jinqiu Gui’ under different temperature treatments were investigated.ResultsCompared to the control (19 °C), high temperature (32 °C) changed the floral color from yellow to yellowish-white with higher lightness (L*) value and lower redness (a*) value, while low temperature (15 °C) turned the floral color from yellow to pale orange with decreased L* value and increased a* value. Total carotenoid content and the content of individual carotenoids (α-carotene, β-carotene, α-cryptoxanthin, β-cryptoxanthin, lutein and zeaxanthin) were inhibited by high temperature, but were enhanced by low temperature. Lower carotenoid accumulation under high temperature was probably attributed to transcriptional down-regulation of the biosynthesis gene OfPSY1, OfZ-ISO1 and OfLCYB1, and up-regulation of degradation genes OfNCED3, OfCCD1-1, OfCCD1-2, and OfCCD4-1. Up-regulation of OfLCYB1, and down-regulation of OfNCED3 and OfCCD4-1 were predicted to be involved in low-temperature-regulated carotenoid accumulation. Luciferase assays showed that the promoter activity of OfLCYB1 was activated by low temperature, and repressed by high temperature. However, the promoter activity of OfCCD4-1 was repressed by low temperature, and activated by high temperature.ConclusionsOur study revealed that high temperature suppressed the floral coloration by repressing the expression of carotenoid biosynthesis genes, and activating the expression of carotenoid degradation genes. However, the relative low temperature had opposite effects on floral coloration and carotenoid biosynthesis in sweet osmanthus. These results will help reveal the regulatory mechanism of temperature on carotenoid accumulation in the petals of sweet osmanthus.

Cloning and characterization ofRARs andRXRs from noble scallopChlamys nobilis, a bivalve rich in carotenoids

The noble scallop Chlamys nobilis that rich in carotenoids is one of the most popular scallop species for aquaculture. Very little is known whether bivalve SRB-like-3 gene expression is regulated by retinoic acid receptor (RAR) and/or retinoic X receptor (RXR). In this study, the full-length cDNA of RAR and RXR genes of C. nobilis was cloned and characterized for the first time, and then, the tissue differential expression of RAR and RXR mRNA in polymorphic C. nobilis was assessed. The roles of RAR and RXR in carotenoid accumulation in C. nobilis were assessed by manipulating the carotenoid content in tissues of C. nobilis via inhibiting the expression of SRB-like-3 gene. The results revealed that two isoforms of RAR (cnRARa (1958 bp/434 aa) and cnRARb (1901 bp/415 aa)) and four RXR isoforms (cnRXRa (1353-bp/450 aa), cnRXRb (1341-bp/446 aa), cnRXRc (1298-bp/436 aa) and cnRXRd (1286-bp/432 aa)) were cloned and characterized from C. nobilis. The reduction of carotenoid content caused by inhibition of SRB-like-3 gene induced the up-regulation of RAR and RXR genes, suggesting that RAR and RXR genes may play a role in the regulation of carotenoid accumulation in haemolymph of C. nobilis. The findings of this study provide important clues for the regulation mechanism of total carotenoid accumulation in C. nobilis.

A single amino acid change at position 96 (Arg to His) of the sweetpotato Orange protein leads to carotenoid overaccumulation.

IbOr-R96H resulted in carotenoid overaccumulation and enhanced abiotic stress tolerance in transgenic sweetpotato calli. The Orange (Or) protein is involved in the regulation of carotenoid accumulation and tolerance to various environmental stresses. Sweetpotato IbOr, with strong holdase chaperone activity, protects a key enzyme, phytoene synthase (PSY), in the carotenoid biosynthetic pathway and stabilizes a photosynthetic component, oxygen-evolving enhancer protein 2-1 (PsbP), under heat and oxidative stresses in plants. Previous studies of various plant species demonstrated that a single-nucleotide polymorphism (SNP) from Arg to His in Or protein promote a high level of carotenoid accumulation. Here, we showed that the substitution of a single amino acid at position 96 (Arg to His) of wild-type IbOr (referred to as IbOr-R96H) dramatically increases carotenoid accumulation. Sweetpotato calli overexpressing IbOr-WT or IbOr-Ins exhibited 1.8- or 4.3-fold higher carotenoid contents than those of the white-fleshed sweetpotato Yulmi (Ym) calli, and IbOr-R96H overexpression substantially increased carotenoid accumulation by up to 23-fold in sweetpotato calli. In particular, IbOr-R96H transgenic calli contained 88.4-fold higher levels of β-carotene than those in Ym calli. Expression levels of carotenogenesis-related genes were significantly increased in IbOr-R96H transgenic calli. Interestingly, transgenic calli overexpressing IbOr-R96H showed increased tolerance to salt and heat stresses, with similar levels of malondialdehyde to those in calli expressing IbOr-WT or IbOr-Ins. These results suggested that IbOr-R96H is a useful target for the generation of efficient industrial plants, including sweetpotato, to cope with growing food demand and climate change by enabling sustainable agriculture on marginal lands.

Alteration of flower colour in Ipomoea nil through CRISPR/Cas9-mediated mutagenesis of carotenoid cleavage dioxygenase 4.

Japanese morning glory, Ipomoea nil, exhibits a variety of flower colours, except yellow, reflecting the accumulation of only trace amounts of carotenoids in the petals. In a previous study, we attributed this effect to the low expression levels of carotenogenic genes in the petals, but there may be other contributing factors. In the present study, we investigated the possible involvement of carotenoid cleavage dioxygenase (CCD), which cleaves specific double bonds of the polyene chains of carotenoids, in the regulation of carotenoid accumulation in the petals of I. nil. Using bioinformatics analysis, seven InCCD genes were identified in the I. nil genome. Sequencing and expression analyses indicated potential involvement of InCCD4 in carotenoid degradation in the petals. Successful knockout of InCCD4 using the CRISPR/Cas9 system in the white-flowered cultivar I. nil cv. AK77 caused the white petals to turn pale yellow. The total amount of carotenoids in the petals of ccd4 plants was increased 20-fold relative to non-transgenic plants. This result indicates that in the petals of I. nil, not only low carotenogenic gene expression but also carotenoid degradation leads to extremely low levels of carotenoids.

A focus on the regulation of carotenoid accumulation in carrot root

Carotenoids are important plant metabolites considered as beneficial for human health. Provided by fruits and vegetables, they are supposed to be implicated in preventing several chronic diseases. In plants, carotenoids play multiple roles as antioxidant molecules. In light-exposed organs, they also act as photosynthesis accessory pigments and pollinator or disseminator attractors. However, in underground organs, like tuber or root, their role is not clearly understood. Carrot is one of the most important sources of dietary carotenoids due to high content in root. Moreover, the large genetic diversity of this species makes it a suitable model to study carotenogenesis. This diversity results in a differential accumulation of carotenoids: mostly β-carotene, α-carotene, lycopene and lutein, leading to various root colors. Although the carotenoid biosynthetic pathway is well-characterized, basic knowledge of carotenogenesis regulation in roots is still lacking. It is generally considered that carotenoid biosynthesis may be controlled at distinct levels: allelic polymorphism, transcriptional regulation, chromoplast differentiation and root development. Previous works have been conducted to elucidate how those different regulation scales impact carotenoid accumulation in carrots. For instance, single nucleotide polymorphisms detected in carotenoid biosynthesis genes like PSY are correlated with root color. However, little is known about the other types of regulation in carrot. In relation with these intracellular mechanisms, external factors may affect carotenoid accumulation as demonstrated for other plant secondary metabolites. This presentation is an overview of the current knowledge about the regulation of carotenoid accumulation in carrot root and the remaining questions to be addressed.

Correlations of carotenoid content and transcript abundances for fibrillin and carotenogenic enzymes in Capsicum annum fruit pericarp

The fruits of Capsicum spp. are especially rich sites for carotenoid synthesis and accumulation, with cultivar-specific carotenoid accumulation profiles. Differences in chromoplast structure as well as carotenoid biosynthesis are correlated with distinct carotenoid accumulations and fruit color. In the present study, the inheritance of chromoplast shape, carotenoid accumulation profiles, and transcript levels of four genes were measured. Comparisons of these traits were conducted using fruit from contrasting variants, Costeño Amarillo versus Costeño Red, and from F1 hybrids; crosses between parental lines with novel versions of these traits. Intermediate chromoplast shapes were observed in the F1, but no association between specific carotenoid accumulation and chromoplast shape was detected. Increased total carotenoid content was associated with increased β-carotene and violaxanthin content. Transcript levels for phytoene synthase (Psy) and β-carotene hydroxylase (CrtZ-2) were positively correlated with increased levels of specific carotenoids. No correlation was detected between transcript levels of capsanthin/capsorubin synthase (Ccs) and carotenoid composition or chromoplast shape. Transcript levels of fibrillin, were differentially correlated with specific carotenoids, negatively correlated with accumulation of capsanthin, and positively correlated with violaxanthin. The regulation of carotenoid accumulation in chromoplasts in Capsicum fruit continues to be a complex process with multiple steps for control.

Modification of Carotenoid Levels by Abscission Agents and Expression of Carotenoid Biosynthetic Genes in ‘Valencia’ Sweet Orange

The effect of 5-chloro-3-methyl-4-nitro-1H-pyrazole (CMNP) and ethephon on peel color, flavedo carotenoid gene expression, and carotenoid accumulation was investigated in mature 'Valencia' orange ( Citrus sinensis L. Osbeck) fruit flavedo at three maturation stages. Abscission agent application altered peel color. CMNP was more effective than ethephon in promoting green-to-red (a) and blue-to-yellow (b) color at the middle and late maturation stages and total carotenoid changes at all maturation stages. Altered flow of carotenoid precursors during maturation due to abscission agents was suggested by changes in phytoene desaturase (Pds) and ζ-carotene desaturase (Zds) gene expression. However, each abscission agent affected downstream expression differentially. Ethephon application increased β-carotene hydroxilase (β-Chx) transcript accumulation 12-fold as maturation advanced from the early to middle and late stages. CMNP markedly increased β- and ε-lycopene cyclase (Lcy) transcript accumulation 45- and 15-fold, respectively, at midmaturation. Patterns of carotenoid accumulation in flavedo were supported in part by gene expression changes. CMNP caused greater accumulation of total flavedo carotenoids at all maturation stages when compared with ethephon or controls. In general, CMNP treatment increased total red carotenoids more than ethephon or the control but decreased total yellow carotenoids at each maturation stage. In control fruit flavedo, total red carotenoids increased and yellow carotenoids decreased as maturation progressed. Trends in total red carotenoids during maturation were consistent with measured a values. Changes in carotenoid accumulation and expression patterns in flavedo suggest that regulation of carotenoid accumulation is under transcriptional, translational, and post-translational control.

Regulation of carotenoid accumulation in plants

Abstract Carotenoids are plant secondary metabolites with a range of beneficial physiological, health and industrial traits. In this review, we summarize the carotenoid biosynthesis pathway and provide an update on research into its regulation in plants. We discuss some factors that determine the steady-state levels of carotenoids in different plant organs and tissues. These factors include the flux through the biosynthesis pathway, and how certain steps represent rate-limiting (bottlenecks), that were exploited in the metabolic engineering of carotenoids. In addition, we discuss carotenoid catabolism, storage and sequestration, and transcriptional and epigenetic regulation as factors affecting the rate of carotenoid accumulation.

Regulation of carotenoid accumulation and the expression of carotenoid metabolic genes in citrus juice sacs in vitro

In the present study, to investigate the mechanisms regulating carotenoid accumulation in citrus, a culture system was set up in vitro with juice sacs of three citrus varieties, Satsuma mandarin (Citrus unshiu Marc.), Valencia orange (Citrus sinensis Osbeck), and Lisbon lemon (Citrus limon Burm.f.). The juice sacs of all the three varieties enlarged gradually with carotenoid accumulation. The changing patterns of carotenoid content and the expression of carotenoid metabolic genes in juice sacs in vitro were similar to those ripening on trees in the three varieties. Using this system, the changes in the carotenoid content and the expression of carotenoid metabolic genes in response to environmental stimuli were investigated. The results showed that carotenoid accumulation was induced by blue light treatment, but was not affected by red light treatment in the three varieties. Different regulation of CitPSY expression, which was up-regulated by blue light while unaffected by red light, led to different changes in carotenoid content in response to these two treatments in Satsuma mandarin and Valencia orange. In all three varieties, increases in carotenoid content were observed with sucrose and mannitol treatments. However, the accumulation of carotenoid in the two treatments was regulated by distinct mechanisms at the transcriptional level. With abscisic acid (ABA) treatment, the expression of the genes investigated in this study was up-regulated in Satsuma mandarin and Lisbon lemon, indicating that ABA induced its own biosynthesis at the transcriptional level. This feedback regulation of ABA led to decreases in carotenoid content. With gibberellin (GA) treatment, carotenoid content was significantly decreased in the three varieties. Changes in the expression of genes related to carotenoid metabolism varied among the three varieties in response to GA treatment. These results provided insights into improving carotenoid content and composition in citrus during fruit maturation.