Carotenoid Metabolism Research Articles

Histone deacetylase SlHDA7 impacts fruit ripening and shelf life in tomato.

Fruit ripening depends on the accurate control of ripening-related genes expression, with histone deacetylases (HDACs) playing crucial roles in transcriptional regulation. However, the functions of HDACs in fruit maturation remain largely unexplored. Here, we show that SlHDA7 acts as a suppressor of fruit ripening and functions as an H4ac HDAC in tomato. Deletion of SlHDA7 accelerated fruit ripening, while overexpression of SlHDA7 delayed the maturation process. Additionally, ethylene production and carotenoid biosynthesis significantly increased in slhda7 mutant fruits but decreased in SlHDA7-overexpressing fruits. Furthermore, SlHDA7 repress the expression of ethylene production and signaling, carotenoid metabolism, cell wall modification, and transcriptional regulation-related genes. RT-qPCR and ChIP-qPCR analyses indicated that SlHDA7 may deacetylate H4ac, leading to reduced transcript levels of ACO1, GGPPS2, Z-ISO, EXP1, and XYL1 mRNA, consequently suppressing fruit ripening. Moreover, SlHDA7 suppresses fruit ripening by targeting specific ripening-associated transcription factors (TFs) like RIN, FUL1, and ERF.E1, ultimately leading to delayed ripening and prolonged fruit shelf life. In summary, our findings indicate that SlHDA7 negatively modulates tomato fruit maturation by adjusting H4ac levels of these ripening-associated genes and key TFs.

The abscisic acid-responsive transcriptional regulatory module CsERF110–CsERF53 orchestrates citrus fruit coloration

Carotenoid biosynthesis is closely associated with abscisic acid (ABA) during the ripening process of non-climacteric fruits, but the regulatory mechanism that links ABA signaling to carotenoid metabolism remains largely unclear. Here, we identified two master regulators of ABA-mediated citrus fruit coloration, CsERF110 and CsERF53, which activate the expression of carotenoid metabolism genes (CsGGPPS, CsPSY, CsPDS, CsCRTISO, CsLCYB2, CsLCYE, CsHYD, CsZEP, and CsNCED2) to facilitate carotenoid accumulation. Further investigations showed that CsERF110 not only activates the expression of CsERF53 by binding to its promoter but also interacts with CsERF53 to form the transcriptional regulatory module CsERF110–CsERF53. We also discovered a positive feedback regulatory loop between the ABA signal and carotenoid metabolism regulated by the transcriptional regulatory module CsERF110–CsERF53. Our results reveal that the CsERF110–CsERF53 module responds to ABA signaling, thereby orchestrating citrus fruit coloration. Considering the importance of carotenoid content for citrus and many other carotenoid-rich crops, the revelation of molecular mechanisms that underlie ABA-mediated carotenoid biosynthesis in plants will facilitate the development of transgenic/gene-editing approaches, further contributing to improving the quality of citrus and other carotenoid-rich crops.

Metabolomic and Transcriptomic Analysis of Unique Floral Coloration in Osmanthus fragrans Cultivars

The floral color phenotypes of Osmanthus fragrans cultivars range from light yellow to orange yellow, with ‘Yanzhi Hong’ being the only reported cultivar with a red color. However, the underlying reason for this unique floral coloration remains unclear. The study conducted targeted metabolomics and transcriptomics analyses on the petals of ‘Yanzhi Hong’ at both initial and peak flowering stages. Candidate gene expression was validated, and expression levels of the petals of three cultivars were compared using RT-qPCR. The results revealed the presence of 27 components in the petals of ‘Yanzhi Hong’, including 5 carotenoids, 8 xanthophylls, and 14 xanthophyll esters. Notably, lycopene was detected in abundance for the first time in O. fragrans cultivars. Carotenes accounted for 78.82 ± 3.17% and 91.19 ± 1.69% of the total carotenoid content in petals during the initial and peak flowering stages, respectively, with all carotene contents increasing during the peak flowering period. β-carotene, lycopene, and γ-carotene were identified as the top three carotene components in petals during both initial and full flowering stages. The unique blush red color of ‘Yanzhi Hong’ petals could be attributed to the low content of α-carotene and the rich accumulation of lycopene. Furthermore, a total of 1550 differentially expressed genes (DEGs) were identified in petals at the peak flowering stage relative to the initial flowering stage, with 1003 genes being downregulated and 547 genes being upregulated during the full flowering stage. There are 926 differentially expressed genes (DEGs) annotated in the Gene Ontology (GO) database. Among these DEGs, those that were downregulated and upregulated during the peak flowering period showed significant enrichment in carbohydrate metabolism and oxidation–reduction processes, respectively. The Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis identified 14 structural genes associated with phenylpropanoid biosynthesis and 7 structural genes linked to carotenoid biosynthesis. Expression levels of candidate genes involved in carotenoid biosynthesis were examined in the petals of three cultivars (‘Yanzhi Hong’, ‘Liuye Jingui’, and ‘Gecheng Dangui’) at both the initial and peak flowering stages. The results indicated that the decreased expression of LYG009054 (LYCE) and LYG018651 (LYCB) in ‘Yanzhi Hong’ resulted in higher lycopene accumulation and lower α-carotene content in the petals. This study offers valuable insights into the mechanisms underlying the unique flower color phenotype of O. fragrans, proving a basis for further research on carotenoid metabolism pathways and the breeding of new cultivars with a variety of flower colors in O. fragrans.

A comprehensive physiological and -Omic analysis of trypsin-mediated protection of green pepper fruits from chilling injury

Chilling injury (CI) in green pepper fruits during low-temperature storage causes a significant decline in quality. The present study utilized physiological, transcriptomic, and metabolomic analyses to idneitfy the mechanisms by which trypsin mitigates CI in green peppers stored at 4 °C for 8 days, followed by 3 days of shelf life. Results indicated that the trypsin treatment significantly reduced electrolyte leakage and the CI index in peppers, effectively extending their shelf life and preserving postharvest quality. After 4 days of storage, comparative -omic analyses identified 2514 differentially expressed genes (DEGs) and 397 differentially abundant metabolites (DAMs) between trypsin-treated and control peppers. The trypsin treatment induced changes in sugar metabolism, modulating the expression of HK, SUS, INV, and GLGC, which affected the abundance of metabolites such as CDP-glucose and α-D-p-glucose. Trypsin also enhanced carotenoid metabolism, altering the abundance of rhodopinal glucoside, 1′-hydroxyl-γ-carotene glucoside, and farnesyl 1-PP, and influencing the expression of PDS, CRTH, CRTB, and LUT5. Notably, the trypsin treatment activated the mitogen-activated protein kinase (MAPK) pathway that plays an integral role in the signal transduction of abiotic stress. Differential expression of FLS2, ELF18, PTO, PR1, PTI5, WPKY, MEKK1, and MPK6 genes in the MAPK pathway was observed, which was correlated with CI mitigation in green peppers during cold storage. In conclusion, trypsin is an effective treatment for reducing CI in green peppers during cold storage. The present study provides valuable insights into its physiological and molecular impact on green pepper fruit.

Dietary Supplementation of β-Carotene Reveals miRNAs Involved in the Regulation of Carotenoid Metabolism in Crassostrea gigas

Dietary Supplementation of β-Carotene Reveals miRNAs Involved in the Regulation of Carotenoid Metabolism in Crassostrea gigas

Effects of gamma irradiation treatment on ROS accumulation and carotenoid metabolism in postharvest Cara Cara fruit (Citrus sinensis L. Osbeck) during storage

This study evaluated the effect of low-dose gamma irradiation (0.3–0.9 kGy) on carotenoid accumulation in Cara Cara fruit (Citrus sinensis L. Osbeck) during storage. Additionally, the irradiation-induced ROS (reactive oxygen species) response and transcriptional levels of carotenoid biosynthesis genes were investigated. Immediate irradiation caused a temporary decrease in most carotenoid levels; however, values recovered during storage and were even higher than those of the control, particularly at 0.6 kGy, especially for carotenoid precursors and carotenes. The upregulated expression of psy, zds and lcyb during majority of the storage period, coupled with the strengthened interaction among adjacent carotenoids, might contribute to the enhanced accumulation of carotenoids in irradiated fruit. A highly positive correlation was found among ROS content, total carotenoids, and upstream expression of zds and lcyb, suggesting that the enhanced carotenoid content in irradiated Cara Cara fruits might be regulated by zds and lcyb in response to ROS accumulation. Antioxidant enzymes of APX, SOD, and CAT levels were significantly correlated with ROS accumulation. In summary, gamma irradiation (0.6 kGy) elevated the levels of carotenoids and antioxidant enzymes, which were potentially modulated by ROS in response to irradiation stress.

What Makes a Mimic? Orange, Red, and Black Color Production in the Mimic Poison Frog (Ranitomeya imitator).

Aposematic organisms rely on their conspicuous appearance to signal that they are defended and unpalatable. Such phenotypes are strongly tied to survival and reproduction. Aposematic colors and patterns are highly variable; however, the genetic, biochemical, and physiological mechanisms producing this conspicuous coloration remain largely unidentified. Here, we identify genes potentially affecting color variation in two color morphs of Ranitomeya imitator: the orange-banded Sauce and the redheaded Varadero morphs. We examine gene expression in black and orange skin patches from the Sauce morph and black and red skin patches from the Varadero morph. We identified genes differentially expressed between skin patches, including those that are involved in melanin synthesis (e.g. mlana, pmel, tyrp1), iridophore development (e.g. paics, ppat, ak1), pteridine synthesis (e.g. gch1, pax3-a, xdh), and carotenoid metabolism (e.g. dgat2, rbp1, scarb2). In addition, using weighted correlation network analysis, we identified the top 50 genes with high connectivity from the most significant network associated with gene expression differences between color morphs. Of these 50 genes, 13 were known to be related to color production (gch1, gmps, gpr143, impdh1, mc1r, pax3-a, pax7, ppat, rab27a, rlbp1, tfec, trpm1, xdh).

Physiological and transcriptomic analyses provide new insights into the regulatory mechanisms of accelerated senescence of litchi fruit in response to strigolactones

Strigolactones (SLs), a class of plant hormones that are derived from carotenoid metabolism, play pivotal roles in regulating various physiological processes in plants. However, the action mode of SLs in regulating postharvest physiology of fruits is not well understood. This study aimed to explore the effect of exogenous GR24 (a synthetic analogue of SLs) on litchi senescence and its possible mechanisms based on physiological and transcriptomic analyses. The results demonstrated that GR24 treatment at 0.5 μM accelerated the development of pericarp browning and discoloration in litchi fruit during storage at ambient conditions, which was related to exacerbated oxidative stress and aggravated membrane deterioration, as indicated by increased reactive oxygen species production, membrane permeability and malondialdehyde content. Compared to those in the control fruit, lower activities of antioxidant enzyme (superoxide dismutase, catalase, glutathione reductase, ascorbate peroxidase and glutathione peroxidase) and contents of antioxidants (ascorbic acid and reduced glutathione), but higher prooxidant enzyme (peroxidase) activity were observed in GR24-treated fruit. Transcriptomic analysis revealed that GR-24 treatment downregulated the expression of genes associated with antioxidant system, pentose phosphate pathway, oxidative phosphorylation and energy metabolism, which was aligned with the physiological results. These findings provide insights into the role of SLs in regulating senescence of harvested litchi fruit.

Integrative application of metabolomics and transcriptomics provides new insights into carotenoid biosynthesis during Rosa rugosa hips ripening

Rosa rugosa, an ornamental plant with medicinal properties, and its red-colored hips are rich in bioactive compounds. However, limited research has been conducted on the accumulation of pigments in its hips and the molecular regulatory mechanism. A comprehensive analysis of carotenoid metabolites at three different stages (mature green (MG), breaker (B) and mature red (MR)) in R. rugosa hips was performed using UPLC-APCI-MS/MS. A total of 18 carotenoids, including eight carotenes and ten xanthophylls, were identified, and their different accumulation patterns were observed in distinct stages. The analysis of differentially expressed genes (DEGs) using gene ontology (GO) highlighted 28 terms. The KEGG pathway analysis revealed that enriched pathways in the biosynthesis of secondary metabolites in MG versus B. RrGGPPS1 was identified as the producer of geranylgeranyl diphosphate (GGPP) through a genetic complementation assay in Escherichia coli and in vitro enzymatic assay. Furthermore, transiently silencing the RrGGPPS1 gene in rose resulted in the reduction of carotenoids in petals. This study provides a foundation for future research on understanding the regulation and biosynthesis of carotenoid metabolism in R. rugosa hips.

CsERF003 enhanced peel coloration by promoting both chlorophyll degradation and carotenoid accumulation in citrus

Uneven coloration is a common phenomenon in citrus fruit during the ripening stage, as affects the appearance and economic value of the fruit. The elevated expression of CsERF003 during the degreening process of both lemon and satsuma mandarin peels was reported. In this research, a similar performance of CsERF003 in the pericarp coloration process was also identified by transcriptome analysis of 'Fengjie 72–1' navel orange and Lane Late navel orange. However, the regulatory mechanism of CsERF003 is not clear yet. Overexpression of CsERF003 could deepen the color of citrus callus and promote peel degreening of Newhall navel orange, which was attributed to the upregulation of genes involved in chlorophyll degradation and carotenoid synthesis. Furthermore, CsERF003 acted as an activator to promote the expression of CsLCYE, but couldn’t activate the expression of CsLCYB1 and CsLCYB2; CsERF003 could also bind to the promoter of CsSGR to activate its expression. Together, our findings shed light on the regulatory mechanism of CsERF003 in chlorophyll degradation and carotenoid accumulation, particularly in the α-branch of carotenoid metabolism. These insights offer valuable perspectives for the genetic enhancement of peel coloration in citrus.

Arbuscular mycorrhizal symbiosis allows to overcome phosphorus deficiency in soilless culture of Lactuca sativa: A phenotypic and transcriptomic analysis

Lettuce (Lactuca sativa L.) is an annual autogamous diploid plant belonging to Asteraceae and is among the top ten most profitable crops worldwide due to its nutritional value. Nevertheless, lettuce is an intensive crop with high input demand, especially fertilisers, both in soil-bound and soilless culture, with negative impact on the environment and production costs. In this context, arbuscular mycorrhizal symbioses could help to reduce the impact of fertilisers, improving plant nutrition, particularly regarding phosphorus, and contributing to growing healthier plants for human consumption. In our work, we compared lettuce plants (cv. Salinas) grown in soilless culture with optimal phosphorus concentration in the nutrient solution, with sub-optimal phosphorus nutrition and with plants grown with sub-optimal phosphorus concentration and inoculated with the fungus Funneliformis mosseae before transplanting.Higher levels of primary and secondary metabolites along with increased biomass were observed for mycorrhizal plants compared to lettuces grown with optimal and sub-optimal concentrations of phosphate. Gene expression profile was analysed in both roots and leaves, and transcriptomic values were associated with growth and biochemical parameters. Three-thousand and fifty-seven genes were differentially regulated by mycorrhizal symbiosis and 2,606 genes by optimal phosphate nutrition.Different genes related to photosynthesis, solute transport, metabolism of phytohormones, redox homeostasis, and transcriptional regulation resulted differentially regulated between culture conditions. Mycorrhizal plants also boosted the activation of genes involved in phenylpropanoids and carotenoids metabolism. In conclusion, growth, biochemical, and transcriptomic data show that symbiotic plants benefit both plant growth and leaf content of health promoting phytochemicals through genetic pathways that largely differed those activated in plants grown with optimal phosphorus supply.

Genome-wide association study reveals candidate genes critical for skin pigmentation in common carp (Cyprinus carpio) strains including koi

The differentiation and variation of body color in fish is an important component of biological evolution and phylogenetic research, and is influenced by several factors such as heredity, nutrition, physiological hormones and rearing conditions, with heredity being the most critical factor. An improved comprehension of the genetic regulation in different carp populations will facilitate future applications of precision breeding and pigment cell development-related genes editing. In this study, we used restriction site-associated DNA sequencing (2d-RAD) to determine the distribution characteristics of single nucleotide polymorphisms (SNPs) in eight common carp strains including six koi strains, i.e., Kohaku (Hb), Taisho (Dz), Showa (Zh), Golden (Hj), Matsukawabake (Sch) and Five-color (Ws), and two genetically improved breeding strains, i.e., FFRC No. 2 strain (Fr) and red FFRC strain (Hfr), and then SNP markers to resolve genetic information on the population structure and skin color formation of these strains. We found that most individuals of eight strains were clearly divided into eight clades. Genetic diversity within Fr, Sch and Ws is relatively high, while it is low within Dz, Hb and Hfr. A comparison between the populations revealed that Hfr and Ws have the highest degree of genetic differences, while Hb and Dz have the lowest. The GWAS analysis for two strategies identified several SNPs that are significantly related to skin color variation and affect melanin synthesis (ephrinb2, slc22a23, herc2, ephb2), carotenoid metabolism (oca2, bcmo1, bco2) and circadian rhythm(cipc). To summarize, our study provides some information on the genetic structure and diversity of Japanese koi and Chinese FFRC carp. Furthermore, based on the data obtained on relevant genes related to skin color differentiation and pigmentation, it can provide a theoretical basis for the subsequent integration of dominant traits and precision breeding in carps.

ZmPTOX1, a plastid terminal oxidase, contributes to redox homeostasis during seed development and germination.

Maize plastid terminal oxidase1 (ZmPTOX1) plays a pivotal role in seed development by upholding redox balance within seed plastids. This study focuses on characterizing the white kernel mutant 3735 (wk3735) mutant, which yields pale-yellow seeds characterized by heightened protein but reduced carotenoid levels, along with delayed germination compared to wild-type (WT) seeds. We successfully cloned and identified the target gene ZmPTOX1, responsible for encoding maize PTOX-a versatile plastoquinol oxidase and redox sensor located in plastid membranes. While PTOX's established role involves regulating redox states and participating in carotenoid metabolism in Arabidopsis leaves and tomato fruits, our investigation marks the first exploration of its function in storage organs lacking a photosynthetic system. Through our research, we validated the existence of plastid-localized ZmPTOX1, existing as a homomultimer, and established its interaction with ferredoxin-NADP+ oxidoreductase 1 (ZmFNR1), a crucial component of the electron transport chain (ETC). This interaction contributes to the maintenance of redox equilibrium within plastids. Our findings indicate a propensity for excessive accumulation of reactive oxygen species (ROS) in wk3735 seeds. Beyond its known role in carotenoids' antioxidant properties, ZmPTOX1 also impacts ROS homeostasis owing to its oxidizing function. Altogether, our results underscore the critical involvement of ZmPTOX1 in governing seed development and germination by preserving redox balance within the seed plastids.

Histone H3K27 demethylase SlJMJ3 modulates fruit ripening in tomato.

The histone lysine (K) demethylase 4 (KDM4/JHDM3) subfamily of jumonji domain-containing demethylases (JMJs) has been implicated in various aspects of plant development. However, their involvement in regulating the ripening of fleshy fruits remains unclear. In this study, we identified SlJMJ3, a member of the KDM4/JHDM3 family, as an H3K27me3 demethylase in tomato (Solanum lycopersicum) that plays an important role in fruit ripening regulation. Overexpression of SlJMJ3 leads to accelerated fruit ripening, whereas loss of function of SlJMJ3 delays this process. Furthermore, we determined that SlJMJ3 exerts its regulatory function by modulating the expression of multiple ripening-related genes involved in ethylene biosynthesis and response, carotenoid metabolism, cell wall modification, transcriptional control, and DNA methylation modification. SlJMJ3 binds directly to the promoters of ripening-related genes harboring the CTCTGYTY motif and activates their expression. Additionally, SlJMJ3 reduces the levels of H3K27me3 at its target genes, thereby upregulating their expression. In summary, our findings highlight the role of SlJMJ3 in the regulation of fruit ripening in tomato. By removing the methyl group from trimethylated histone H3 lysine 27 at ripening-related genes, SlJMJ3 acts as an epigenetic regulator that orchestrates the complex molecular processes underlying fruit ripening.

Astaxanthin induces plant tolerance against cadmium by reducing cadmium uptake and enhancing carotenoid metabolism for antioxidant defense in wheat (Triticum aestivum L.)

Soil cadmium (Cd) contamination poses a significant threat to global food security and the environment. Astaxanthin (AX), a potent biological antioxidant belonging to the carotenoid group, has been demonstrated to confer tolerance against diverse abiotic stresses in plants. This study investigated the potential of AX in mitigating Cd-induced damage in wheat seedlings. Morpho-physiological, ultrastructural, and biochemical analyses were conducted to evaluate the impact of AX on Cd-exposed wheat seedlings. Illumina-based gene expression profiling was employed to uncover the molecular mechanisms underlying the protective effects of AX. The addition of 100 μM AX alleviated Cd toxicity by enhancing various parameters: growth, photosynthesis, carotenoid content, and total antioxidant capacity (T-AOC), while reducing Cd accumulation, malondialdehyde (MDA), and hydrogen peroxide (H2O2) levels. RNA sequencing analysis revealed differentially expressed genes associated with Cd uptake and carotenoid metabolism, such as zinc/iron permease (ZIP), heavy metal-associated protein (HMA), 3-beta hydroxysteroid dehydrogenase/isomerase (3-beta-HSD), and thiolase. These findings suggest that AX enhances Cd tolerance in wheat seedlings by promoting the expression of detoxification and photosynthesis-related genes. This research offers valuable insights into the potential use of AX to address Cd contamination in agricultural systems, highlighting the significance of antioxidant supplementation in plant stress management.

Distinct growth patterns in seedling and tillering wheat plants suggests a developmentally restricted role of HYD2 in salt-stress response

Key messageMutants lacking functional HYD2 homoeologs showed improved seedling growth, but comparable or increased susceptibility to salt stress in tillering plants, suggesting a developmentally restricted role of HYD2 in salt response.Salinity stress threatens global food security by reducing the yield of staple crops such as wheat (Triticum ssp.). Understanding how wheat responds to salinity stress is crucial for developing climate resilient varieties. In this study, we examined the interplay between carotenoid metabolism and the response to salt (NaCl) stress, a specific form of salinity stress, in tetraploid wheat plants with mutations in carotenoid β-hydroxylase 1 (HYD1) and HYD2. Our investigation encompassed both the vulnerable seedling stage and the more developed tillering stage of wheat plant growth. Mutant combinations lacking functional HYD2 homoeologs, including hyd-A2 hyd-B2, hyd-A1 hyd-A2 hyd-B2, hyd-B1 hyd-A2 hyd-B2, and hyd-A1 hyd-B1 hyd-A2 hyd-B2, had longer first true leaves and slightly enhanced root growth during germination under salt stress compared to the segregate wild-type (control) plants. Interestingly, these mutant seedlings also showed decreased levels of neoxanthin and violaxanthin (xanthophylls derived from β-carotene) and an increase in β-carotene in roots. However, tillering hyd mutant and segregate wild-type plants generally did not differ in their height, tiller count, and biomass production under acute or prolonged salt stress, except for decreases in these parameters observed in the hyd-A1 hyd-B1 hyd-A2 hyd-B2 mutant that indicate its heightened susceptibility to salt stress. Taken together, these findings suggest a significant, yet developmentally restricted role of HYD2 homoeologs in salt-stress response in tetraploid wheat. They also show that hyd-A2 hyd-B2 mutant plants, previously demonstrated for possessing enriched nutritional (β-carotene) content, maintain an unimpaired ability to withstand salt stress.

ECR Spotlight – Rebecca Koch

ECR Spotlight is a series of interviews with early-career authors from a selection of papers published in Journal of Experimental Biology and aims to promote not only the diversity of early-career researchers (ECRs) working in experimental biology but also the huge variety of animals and physiological systems that are essential for the ‘comparative’ approach. Rebecca Koch is an author on ‘ Captivity affects mitochondrial aerobic respiration and carotenoid metabolism in the house finch (Haemorhous mexicanus)’, published in JEB. Rebecca is a postdoctoral researcher in the lab of Matthew Toomey, Department of Biological Sciences, University of Tulsa, investigating how birds communicate information during courtship, particularly through the use of coloration.

Exogenous leucine delayed the yellowing of postharvest broccoli by regulating strigolactone and abscisic acid signals based on multi-omics profiling

The yellowing of postharvest broccoli is the immediate manifestation of its quality deterioration, which can cause the loss of commodity value. This study employs a comprehensive analysis integrating transcriptomics and metabolomics to elucidate the effects and potential molecular mechanisms of exogenous leucine on pigment metabolism in postharvest broccoli stored at 10 ± 0.5 °C. Results demonstrate that leucine treatment significantly inhibited the decrease of chlorophyll content and the increase of carotenoid content. Leucine treatment also inhibited the respiration rate and maintained higher vitamin C content, total phenols content and DPPH radical scavenging activity of broccoli. Leucine treatment promoted chlorophyll biosynthesis by up-regulating UROD, PPOX, MC, CHLM, POR, DCVR, MT, and CAS expression while inhibiting chlorophyll liberation and degradation by up-regulating CABs expression and down-regulating NYC1, CLH2, PAO, and PPD expression. Additionally, exogenous leucine alleviated the damage of photosystem I, photosystem II, and photosynthetic electron transport chains in the thylakoid membrane. Furthermore, leucine treatment results in a lower transcriptional level of PDS, LCYB, crtZ, and ZEP, leading to reduced lycopene, zeaxanthin, and β-carotene content. Leucine treatment promotes the biosynthesis of carlactone, a strigolactone (SL) precursor, by up-regulating DWARF27, CCD7, and CCD8 expression. Additionally, leucine treatment down-regulated XDH expression and up-regulated CYP707A expression, inhibiting the biosynthesis and accumulation of abscisic acid (ABA). Consequently, our findings suggest that ABA and SLs may serve as crucial signaling factors in regulating chlorophyll and carotenoid metabolism in leucine-treated broccoli. This study introduces a novel method with theoretical support for delaying the yellowing process in postharvest broccoli.

Captivity affects mitochondrial aerobic respiration and carotenoid metabolism in the house finch (Haemorhous mexicanus).

In many species of animals, red carotenoid-based coloration is produced by metabolizing yellow dietary pigments, and this red ornamentation can be an honest signal of individual quality. However, the physiological basis for associations between organism function and the metabolism of red ornamental carotenoids from yellow dietary carotenoids remains uncertain. A recent hypothesis posits that carotenoid metabolism depends on mitochondrial performance, with diminished red coloration resulting from altered mitochondrial aerobic respiration. To test for an association between mitochondrial respiration and red carotenoids, we held wild-caught, molting male house finches in either small bird cages or large flight cages to create environmental challenges during the period when red ornamental coloration is produced. We predicted that small cages would present a less favorable environment than large flight cages and that captivity itself would decrease both mitochondrial performance and the abundance of red carotenoids compared with free-living birds. We found that captive-held birds circulated fewer red carotenoids, showed increased mitochondrial respiratory rates, and had lower complex II respiratory control ratios - a metric associated with mitochondrial efficiency - compared with free-living birds, though we did not detect a difference in the effects of small cages versus large cages. Among captive individuals, the birds that circulated the highest concentrations of red carotenoids had the highest mitochondrial respiratory control ratio for complex II substrate. These data support the hypothesis that the metabolism of red carotenoid pigments is linked to mitochondrial aerobic respiration in the house finch, but the mechanisms for this association remain to be established.

BnaABF3 and BnaMYB44 regulate the transcription of zeaxanthin epoxidase genes in carotenoid and abscisic acid biosynthesis.

Zeaxanthin epoxidase (ZEP) is a key enzyme that catalyzes the conversion of zeaxanthin to violaxanthin in the carotenoid and abscisic acid (ABA) biosynthesis pathways. The rapeseed (Brassica napus) genome has 4 ZEP (BnaZEP) copies that are suspected to have undergone subfunctionalization, yet the 4 genes' underlying regulatory mechanisms remain unknown. Here, we genetically confirmed the functional divergence of the gene pairs BnaA09.ZEP/BnaC09.ZEP and BnaA07.ZEP/BnaC07.ZEP, which encode enzymes with tissue-specific roles in carotenoid and ABA biosynthesis in flowers and leaves, respectively. Molecular and transgenic experiments demonstrated that each BnaZEP pair is transcriptionally regulated via ABA-responsive element-binding factor 3 s (BnaABF3s) and BnaMYB44s as common and specific regulators, respectively. BnaABF3s directly bound to the promoters of all 4 BnaZEPs and activated their transcription, with overexpression of individual BnaABF3s inducing BnaZEP expression and ABA accumulation under drought stress. Conversely, loss of BnaABF3s function resulted in lower expression of several genes functioning in carotenoid and ABA metabolism and compromised drought tolerance. BnaMYB44s specifically targeted and repressed the expression of BnaA09.ZEP/BnaC09.ZEP but not BnaA07.ZEP/BnaC07.ZEP. Overexpression of BnaA07.MYB44 resulted in increased carotenoid content and an altered carotenoid profile in petals. Additionally, RNA-seq analysis indicated that BnaMYB44s functions as a repressor in phenylpropanoid and flavonoid biosynthesis. These findings provide clear evidence for the subfunctionalization of duplicated genes and contribute to our understanding of the complex regulatory network involved in carotenoid and ABA biosynthesis in B. napus.