Carotenoid metabolism in plants

Blue light-induced MiBBX24 and MiBBX27 simultaneously promote peel anthocyanin and flesh carotenoid biosynthesis in mango

Blue light simultaneously enhances anthocyanin and carotenoid biosynthesis in mango (Mangifera indica L.) fruit peel and flesh, respectively, but the mechanism remains unclear. In this study, two blue light-triggered zinc-finger transcription factors, MiBBX24 and MiBBX27, that positively regulate anthocyanin and carotenoid biosynthesis in mango fruit were identified. Both MiBBXs transcriptionally activate the expression of MiMYB1, a positive regulator of anthocyanin biosynthesis. Furthermore, both MiBBXs also trigger the expression of a phytoene synthase gene (MiPSY), which is essential for carotenoid biosynthesis. Ectopic expression of MiBBX24 or MiBBX27 in Arabidopsis increased anthocyanin contents, and their positive effects on anthocyanin accumulation in mango peel were confirmed through transient overexpression and virus-induced silencing. Transient expression of MiBBX24 or MiBBX27 in tomato (Solanum lycopersicum) and mango fruit flesh increased the carotenoid content, while the virus-induced silencing of MiBBX24 or MiBBX27 in the mango fruit flesh decreased carotenoid accumulation. Overall, our study results reveal that MiBBX24 and MiBBX27 simultaneously promote the biosynthesis of anthocyanin and carotenoids biosynthesis in mango fruit peel and flesh under blue light, indicating that BBX-mediated dual effects on physiological functions contribute to mango fruit pigment accumulation. Furthermore, we herein shed new light on the simultaneous transcriptional regulatory effects of a single factor on the biosynthesis of different plant pigments.

Maize kernel nutritional quality-an old challenge for modern breeders

MAIN CONCLUSION

This article offers a comprehensive overview of the starch, protein, oil, and carotenoids content in maize kernels, while also outlining future directions for research in this area. Maize is one of the most important cereal crops globally. Maize kernels serve as a vital source of feed and food, and their nutritional quality directly impacts the dietary intake of both animals and humans. Maize kernels contain starch, protein, oil, carotenoids, and a variety of vitamins and minerals, all of which are important for maintaining life and promoting health. This review presents the current understanding of the content of starch, protein, amino acids, oil, and carotenoids in maize kernels, while also highlighting knowledge gaps that need to be addressed.

Genetic, metabolomic and transcriptomic analyses of the cotton yellow anther trait

In the fiber industry, cotton (Gossypium hirsutum L.) is an important crop. One of the most important morphology traits of plants is the color of the anthers, is closely related to pollen fertility and stress resistance. Upland cotton anthers appear white, while island cotton and many wild cotton species have yellow anthers. Carotenoids are natural pigments in plants which involved in many metabolic processes, including photosynthesis, photoprotection, photomorphogenesis, growth and development. Here, we characterized the yellow anther trait of G. hirsutum. Carotenoid and flavonoid profiles in the yellow anthers were greatly altered compared to that in the white anthers, indicating that both carotenoids and flavonoids contribute to the yellow anther phenotype. Map-based cloning identified GhYA (GH_A05G4013) encoding a phytoene synthase to be the candidate gene responsible for anther coloration. GhYA is predominantly expressed in anthers, with its expression level gradually decreasing with the development of anthers. Haplotype analysis revealed that white anthers are associated with two haplotypes, with X74 belonging to HAP1. Through evolutionary analysis, it was found that although there are many white anther Germplasm in upland cotton, the two types of white anther haplotypes were mutated from yellow anthers respectively. Comparative transcriptome analysis between the yellow anther and white anther accessions revealed differentially expressed genes related to both the carotenoid and flavonoid biosynthesis pathways, in line with the changed profiles of the two types of metabolites in yellow anthers; meanwhile, it also indicates potential cross-talk between the flavonoid and carotenoid pathways. According to the results, the PSY gene is critical for the regulation of carotenoids accumulation in cotton anthers.

Comprehensive analysis of metabolomics and transcriptomics reveals varied tepal pigmentation across Gloriosa varieties

Gloriosa L. possesses exceptional ornamental value, with its floral hues exhibiting a wide range of variations. In this study, we employed sophisticated colorimetry, Ultra Performance Liquid Chromatography-Tandem Mass Spectrometry (UPLC-MS/MS), and transcriptome sequencing to investigate the phenotypic expression of tepal colors, the composition of carotenoids and anthocyanins, and the differential gene expression in four Gloriosa varieties during their full bloom phase. Our findings revealed that the redness of the tepals, indicated by higher a* values, increased with the intensity of the red hue, while lighter colors corresponded to higher L* values. Metabolomic analysis identified 50 carotenoids and 60 anthocyanins. It was observed that carotenoids primarily influence the yellow and orange color of Gloriosa tepals, with β-carotene, lutein, and zeaxanthin being the predominant carotenoids. Anthocyanins serve as the principal coloring agents in the orange, red and purple tepals of Gloriosa. High levels and proportions of cyanidins and pelargonidins are key contributors to the formation of red and purple tepals, while high levels and proportions of peonidins also play a significant role in purple coloration. In contrast, the presence of high levels and proportions of pelargonidins alone is a crucial factor in the formation of orange tepals. Transcriptomic data unearthed 57 and 92 candidate differentially expressed genes (DEGs) belong to carotenoid and anthocyanin biosynthesis pathway, respectively, with PSY, PDS, DFR, and ANS genes considered as critical genes for the differential accumulation of pigments of Gloriosa tepals. Weighted gene co-expression network analysis (WGCNA) revealed significant co-expression patterns between 217 transcription regulatory factors (TFs) and 8 carotenoid biosynthesis genes, and between 194 TFs and 41 anthocyanin biosynthesis genes. qRT-PCR verified the expression patterns of four carotenoid biosynthesis-related genes, eight anthocyanin biosynthesis-related genes, and three transcription regulatory factors. It was found that Cluster-121969.6 (MYB) gene is specifically expressed in the tepals of the four varieties (compared to stems and leaves) and shows a high consistency with the trend of anthocyanin content changes. This research provides new insights into the mechanisms underlying the formation of diverse floral colors in Gloriosa tepals.

Deposition of sulfur by Spartina alterniflora promoted its ecological adaptability in cadmium-polluted coastal wetlands

Invasive Spartina alterniflora poses a significant threat to coastal wetland ecosystems. This study investigated the role of sulfur (S) in facilitating the invasion of S. alterniflora in cadmium (Cd)-contaminated coastal wetlands by greenhouse-control-experiment. Results demonstrate that increased S deposition significantly enhanced the formation of acid-volatile sulfur in sediments, thereby reducing the bioavailability of Cd to plants by 41%. Additionally, S supplementation improved plant nutrient uptake and stress tolerance by increasing the C/N ratio and the concentrations of essential mineral elements. These physiological and biochemical changes, including enhanced photosynthesis, increased carbohydrate storage, and improved antioxidant capacity, ultimately contributed to increased shoot and root biomass production by 15% and 31% respectively, and the competitive ability of S. alterniflora. The findings of this study highlight the critical role of S in promoting the invasion of S. alterniflora. Effective strategies can be developed to control the spread of S. alterniflora and protect coastal ecosystems.

Natural pigments: innovative extraction technologies and their potential application in health and food industries

Natural pigments, or natural colorants, are frequently utilized in the food industry due to their diverse functional and nutritional attributes. Beyond their color properties, these pigments possess several biological activities, including antioxidant, anti-inflammatory, anticancer, antibacterial, and neuroprotective effects, as well as benefits for eye health. This review aims to provide a timely overview of the potential of natural pigments in the pharmaceutical, medical, and food industries. Special emphasis is placed on emerging technologies for natural pigment extraction (thermal technologies, non-thermal technologies, and supercritical fluid extraction), their pharmacological effects, and their potential application in intelligent food packaging and as food colorants. Natural pigments show several pharmaceutical prospects. For example, delphinidin (30 µM) significantly inhibited the growth of three cancer cell lines (B16-F10, EO771, and RM1) by at least 90% after 48 h. Furthermore, as an antioxidant agent, fucoxanthin at the highest concentration (50 μg/mL) significantly increased the ratio of glutathione to glutathione disulfide (p < 0.05). In the food industry, natural pigments have been used to improve the nutritional value of food without significantly altering the sensory experience. Moreover, the use of natural pH-sensitive pigments as food freshness indicators in intelligent food packaging is a cutting-edge technological advancement. This innovation could provide useful information to consumers, increase shelf life, and assist in evaluating the quality of packaged food by observing color variations over time. However, the use of natural pigments presents certain challenges, particularly regarding their stability and higher production costs compared to synthetic pigments. This situation underscores the need for further investigation into alternative pigment sources and improved stabilization methods. The instability of these natural pigments emphasizes their tendency to degrade and change color when exposed to various external conditions, including light, oxygen, temperature fluctuations, pH levels, and interactions with other substances in the food matrix.

Assessment of the Photosynthetic Response of Potato Plants Inoculated with Rhizoctonia solani and Treated with Flesh-Colored Potato Extracts Nanoencapsulated with Solid Lipid Nanoparticles

Potato has great nutritional and economic importance in agriculture. However, Rhizoctonia solani represents a significant risk, reducing the yield and quality of potato production. Flesh-colored potato (FCP) extracts show in vitro inhibitory effects against R. solani, although environmental factors may reduce their stability. Solid lipid nanoparticles (SNLs) offer a solution by encapsulating these compounds, preventing degradation, and improving delivery, positioning solid lipid nanoparticles as a promising technology for sustainable extract application. A greenhouse potato assay at two phenological stages under R. solani inoculation was used to evaluate the photosynthetic response (photosynthetic parameters and pigments) to two doses of the nanoencapsulated extract (SNL + FCP). During inoculation and commercial fungicide application, stomatal conductance, the photosynthetic rate, and the internal CO2 concentration increased compared with those of the non-inoculated control (NT), whereas the nanoencapsulated extract maintained levels similar to those of the NT, suggesting the possible regulation of the photosynthetic defense system. In terms of photosynthetic pigments, SLN + FCP maintained chlorophyll concentrations, unlike those in inoculated plants, which significantly decreased. Component analysis revealed that a lower dose primarily increased chlorophyll B synthesis, whereas a higher dose increased chlorophyll A compared with the inoculated control. These findings suggest an improved response from SLN + FCP to commercial fungicides, particularly with respect to photosynthetic pigments. However, further research is needed, and the results indicate promising potential for the eco-friendly control of phytopathogenic fungi in agriculture.

The Potential Application of Nanocarriers in Delivering Topical Antioxidants

The imbalance in the production of reactive oxygen species (ROS) with endogenous antioxidant capacity leads to oxidative stress, which drives many disorders, especially in the skin. In such conditions, supplementing exogenous antioxidants may help the body prevent the negative effect of ROS. However, the skin, as the outermost barrier of the body, provides a perfect barricade, making the antioxidant delivery complicated. Several strategies have been developed to enhance the penetration of antioxidants through the skin, one of which is nanotechnology. This review focuses on utilizing several nanocarrier systems, including nanoemulsions, liposomes, solid lipid nanoparticles (SLNs), nanostructured lipid carriers (NLCs), and polymeric nanoparticles, for transporting antioxidants into the skin. We also reveal ROS formation in the skin and the role of antioxidant therapy, as well as the natural sources of antioxidants. Furthermore, we discuss the clinical application of topical antioxidant therapy concomitantly with the current status of using nanotechnology to deliver topical antioxidants. This review will accelerate the advancement of topical antioxidant therapy.

Bcwf regulates the white petal color in pak choi [Brassica campestris (syn. Brassica rapa) ssp. chinensis]

Flower color is important in determining the ornamental value of Brassica species. However, our knowledge about the regulation of flower color in pak choi [Brassica campestris (syn. Brassica rapa) ssp. chinensis] is limited. In this study, we investigated the molecular mechanism underlying white flower traits in pak choi by analyzing a genetic population with white and yellow flowers. Our genetic analysis revealed that the white trait is controlled by a single recessive gene called Bcwf. Through BSA-Seq and fine mapping, we identified a candidate gene, BraC02g039450.1, which is similar to Arabidopsis AtPES2 involved in carotenoid ester synthesis. Sequence analysis showed some mutations in the promoter region of Bcwf in white flowers. Tobacco transient assay confirmed that these mutations reduce the promoter's activity, leading to downregulation of Bcwf expression in white flowers. Furthermore, the silencing of Bcwf in pak choi resulted in lighter petal color and reduced carotenoid content. These findings provide new insights into the molecular regulation of white flower traits in pak choi and highlight the importance of Bcwf in petal coloring and carotenoid accumulation.

Refining polyploid breeding in sweet potato through allele dosage enhancement

Allele dosage plays a key role in the phenotypic variation of polyploids. Here we present a genome-wide variation map of hexaploid sweet potato that captures allele dosage information, constructed from deep sequencing of 294 hexaploid accessions. Genome-wide association studies identified quantitative trait loci with dosage effects on 23 agronomic traits. Our analyses reveal that sweet potato breeding has progressively increased the dosage of favourable alleles to enhance trait performance. Notably, the Mesoamerican gene pool has evolved towards higher dosages of favourable alleles at multiple loci, which have been increasingly introgressed into modern Chinese cultivars. We substantiated the breeding-driven dosage accumulation through transgenic validation of IbEXPA4, an expansin gene influencing tuberous root weight. In addition, we explored causative sequence variations that alter the expression of the Orange gene, which regulates flesh colour. Our findings illuminate the breeding history of sweet potato and establish a foundation for leveraging allele dosages in polyploid breeding practices.

Recent updates of carotenoid encapsulation by spray-drying technique

Carotenoids are compounds sensitive to environmental factors such as light, heat, and oxygen, which can result in the loss of their properties due to isomerisation and oxidation. To overcome this problem, spray drying encapsulation has been widely used as a method to protect and stabilise carotenoids in different wall materials. This article summarises the findings and research on spray drying encapsulation of carotenoids over the past 15 years, with an emphasis on the importance of controlling the operational conditions of the drying process and the association of different wall materials (proteins and polysaccharides), promising to increase encapsulation efficiency and stabilise carotenoids, with perspectives and trends in applications. The use of spray drying for carotenoid microencapsulation can open up new opportunities for controlled delivery of beneficial compounds. Based on the study, it is expected to provide information for researchers, professionals, and companies interested in the development of functional food products.

Integrative Targeted Metabolomics and Transcriptomics Reveal the Mechanism of Leaf Coloration in Impatiens hawkeri 'Sakimp005'

One of the most important characteristics of ornamental plants is leaf color, which enhances the color of plant landscapes and attracts pollinators for reproduction. The leaves of Impatiens hawkeri 'Sakimp005' are initially green, then the middle part appears yellow, then gradually become white, while the edge remains green. In the study, leaves of I. hawkeri 'Sakimp005', in four developmental stages (S1-G, S2-C, S3-C, and S4-C), were selected for the determination of pigment content, chromaticity values, integrative metabolomics, and transcriptomics analyses. The carotenoid content of leaves varied significantly and regularly at four stages, and the colorimetric values corroborated the phenotypic observations. The results of integrative metabolomics and transcriptomics analysis show that the accumulation of two carotenoids (lutein and zeaxanthin), to different degrees in the leaves of I. hawkeri 'Sakimp005' at four stages, led to the vary yellowing phenomenon. We speculated that the carotenoid biosynthesis (containing two branches: α-branch and β-branch) in leaves by IhLUT1 and IhLUT5 in the α-branch and IhBCH2 genes in the β-branch differed. These findings provide a molecular basis for Impatiens plants' leaf color breeding and improve the knowledge of the leaf color mechanism.

Light Spectral-Ranged Specific Metabolisms of Plant Pigments

Chlorophyll is the primary pigment responsible for capturing light energy during photosynthesis, while carotenoids assist in light absorption and provide photoprotection by dissipating excess energy. Both pigments are essential for plant growth and development, playing distinct and complementary roles in maintaining photosynthetic efficiency and protecting plants from oxidative stress. Because of their function in photosynthesis and photoprotection, chlorophyll and carotenoid accumulation are strongly associated with light conditions, especially blue and red lights, which play key roles in regulating their metabolisms. Despite advancements in understanding pigment metabolism, there remains a limited comprehensive overview of how various parts of the light spectrum influence these pathways throughout the entire process. The effects of other spectral ranges of light, such as green light, far-red light, and UV, are not yet fully understood. This review aims to synthesize recent findings about the regulatory network of chlorophyll and carotenoid pathways under different light spectral bands, emphasizing the interplay between light-regulated transcription factors and genes involved in their biosynthesis and degradation.

Red peel regulator 1 links ethylene response factor 25 and β-citraurin biosynthetic genes to regulate ethylene-induced peel reddening in citrus

The reddish apocarotenoid β-citraurin, produced by CAROTENOID CLEAVAGE DIOXYGENASE 4b (CsCCD4b), is responsible for peel reddening in citrus (Citrus spp.). Ethylene induces the characteristic red color of citrus peel, but the underlying molecular mechanism remains largely unclear. Here, we identified red peel regulator 1 (CsRP1), a trihelix transcriptional activator that regulates ethylene-induced peel reddening by directly binding to a key V-myb avian myeloblastosis viral oncogene homolog (MYB)-binding site in the CsCCD4b promoter, thus activating its transcription. Furthermore, 2 drought-responsive cis-elements in the CsRP1 promoter are bound by the ethylene response factor ethylene response factor 25 (CsERF25). We reconstructed the CsERF25-CsRP1-CsCCD4b transcriptional regulatory cascade through transient expression of CsERF25 and CsRP1 in citrus peel and via stable transformation of citrus calli. In this cascade, CsERF25 expression was induced by ethylene to activate CsRP1 expression, and then, CsRP1 directly induced CsCCD4b transcription to catalyze β-citraurin biosynthesis. CsRP1 and CsERF25 also bound to the promoters of other carotenogenic genes and induced their transcription, thereby promoting β-citraurin accumulation. Collectively, our findings reveal a complex regulatory network modulating ethylene-induced citrus peel reddening and provide innovative strategies for improving the nutritional and esthetic values of citrus and other fruit crops.

Expression profiles of microRNA-mRNA and their potential impact on anthocyanin accumulation in purple petals of Brassica napus

Rapeseed (Brassica napus L.) possesses substantial economic value as an oil, vegetable, and forage crop, while also exhibiting notable ornamental characteristics. Recent advances in flower colour breeding have significantly enhanced the visual appeal of rapeseed, with anthocyanins identified as the primary contributor to the development of red, purple, and pink flowers. However, the mechanisms underlying the synthesis and regulation of anthocyanins during petal coloration in rapeseed are still poorly understood. This research combined miRNA and mRNA expression data from four different color phases, along with degradome analysis, to discover important miRNA-mRNA modules responsible for controlling the accumulation of anthocyanin in purple-flowered rapeseed. In the process of petal development, a grand sum of 247 miRNAs (including 223 known and 24 novel miRNAs) were effectively detected, with 64 of them displaying differential expression patterns. Degradome sequencing was used to conduct a comprehensive analysis of 152 targets for the differential expression miRNAs. Out of these, 108 miRNA-mRNA modules exhibit contrasting expression patterns. Some miRNAs and their corresponding targets have additionally been discovered, potentially playing a role in governing the buildup of anthocyanin in purple-flowered rapeseed. The regulatory modules miR156-SPL9 and miR828-PAP2 composed of miR156b and miR828 and their targets may play a key role in this process. The results offer a thorough analysis of miRNAs linked to the regulation of anthocyanin in B. napus, offering valuable understanding into the regulatory processes that govern miRNA-mediated anthocyanin production in Brassica crops.

Rapid investigation of the alteration in biochemical profile of maize seedlings treated with aluminium oxide nanoparticles using spectroscopic techniques

The present study demonstrates the applicability of non-destructive and rapid spectroscopic techniques, specifically laser-induced fluorescence, ultraviolet-visible, and confocal micro-Raman spectroscopy, as non-invasive, eco-friendly, and robust multi-compound analytical methods for assessing biochemical changes in maize seedling leaves resulting from the treatment of aluminium oxide nanoparticles. The recorded fluorescence spectrum of the leaves shows that the treatment of different concentration of aluminium oxide nanoparticles decreases the chlorophyll content as observed by the increase in fluorescence emission intensity ratio (FIR = I685/I734). The analysis of ultraviolet-visible absorption measurements reveals that the amount of chlorophyll a, chlorophyll b, total chlorophyll and carotenoid decrease for treated plants with respect to untreated seedlings. Likewise, the analysis of the acquired Raman spectrum depicts that the treatment of different concentration of aluminium oxide nanoparticles exhibits toxic effect on the maize plants and reduces the level of biochemicals like cellulose, carbohydrates, carotenoid, lignin, proteins, pectin and aliphatics compared to untreated seedlings. The results obtained in the present study indicate that the effects of the treatment of different concentration of the aluminium oxide nanoparticles on maize seedlings can be estimated at an early stage, rapidly and cost effectively using spectroscopic techniques.

The Mitochondrial Blueprint: Unlocking Secondary Metabolite Production

Mitochondrial metabolism plays a pivotal role in regulating the synthesis of secondary metabolites, which are crucial for the survival and adaptation of organisms. These metabolites are synthesized during specific growth stages or in response to environmental stress, reflecting the organism's ability to adapt to changing conditions. Mitochondria, while primarily known for their role in energy production, directly regulate secondary metabolite biosynthesis by providing essential precursor molecules, energy, and reducing equivalents necessary for metabolic reactions. Furthermore, they indirectly influence secondary metabolism through intricate signaling pathways, including reactive oxygen species (ROS), metabolites, and redox signaling, which modulate various metabolic processes. This review explores recent advances in understanding the molecular mechanisms governing mitochondrial metabolism and their regulatory roles in secondary metabolite biosynthesis, which highlights the involvement of transcription factors, small RNAs, and post-translational mitochondrial modifications in shaping these processes. By integrating current insights, it aims to inspire future research into mitochondrial regulatory mechanisms in Arabidopsis thaliana, Solanum tuberosum, Nicotiana tabacum, and others that may enhance their secondary metabolite production. A deeper understanding of the roles of mitochondria in secondary metabolism could contribute to the development of new approaches in biotechnology applications.

Chemical Diversity of Mediterranean Seagrasses Volatilome

BACKGROUND/OBJECTIVES

Biogenic volatile organic compounds (BVOCs), extensively studied in terrestrial plants with global emissions around 1 PgC yr-1, are also produced by marine organisms. However, benthic species, especially seagrasses, are understudied despite their global distribution (177,000-600,000 km2). This study aims to examine BVOC emissions from key Mediterranean seagrass species (Cymodocea nodosa, Posidonia oceanica, Zostera noltei, and Zostera marina) in marine and coastal lagoon environments.

METHODS

BVOCs were collected using headspace solid-phase microextraction (HS-SPME) using divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) fibers and analyzed by gas chromatography-mass spectrometry (GC-MS).

RESULTS

An important chemical diversity was found with a total of 92 volatile compounds (61 for Z. noltei, 59 for C. nodosa, 55 for P. oceanica, and 51 for Z. marina), from different biosynthetic pathways (e.g., terpenoids, benzenoids, and fatty acid derivatives) and with several types of chemical functions (e.g., alkanes, esters, aldehydes, and ketones) or heteroatoms (e.g., sulfur). No differences in chemical richness or diversity of compounds were observed between species. The four species shared 29 compounds enabling us to establish a specific chemical footprint for Mediterranean marine plants, including compounds like benzaldehyde, benzeneacetaldehyde, 8-heptadecene, heneicosane, heptadecane, nonadecane, octadecane, pentadecane, tetradecane, and tridecanal. PLS-DA and Heatmap show that the four species presented significantly different chemical profiles. The major compounds per species in relative abundance were isopropyl myristate for C. nodosa (25.6%), DMS for P. oceanica (39.3%), pentadecane for Z. marina (42.9%), and heptadecane for Z. noltei (46%).

CONCLUSIONS

These results highlight the potential of BVOCs' emission from seagrass ecosystems and reveal species-specific chemical markers.

The Expression Profile of Genes Related to Carotenoid Biosynthesis in Pepper Under Abiotic Stress Reveals a Positive Correlation with Plant Tolerance

In light of the increasingly adverse environmental conditions and the concomitant challenges to the survival of important crops, there is a pressing need to enhance the resilience of pepper seedlings to extreme weather. Carotenoid plays an important role in plants' resistance to abiotic stress. Nevertheless, the relationship between carotenoid biosynthesis and sweet pepper seedlings' resistance to different abiotic stresses remains uncertain. In this study, the carotenoid content in abiotic-stressed sweet pepper seedling roots was determined, revealing that carotenoid content was extremely significantly elevated by more than 16-fold under salt stress, followed by drought stress (8-fold), and slightly elevated by only about 1-fold under waterlogging stress. After that, serine/threonine-protein phosphatase 2A (PP2A) was found to be the suitable reference gene (RG) in sweet pepper seedling roots under different abiotic stresses by using RT-qPCR and RefFinder analysis. Subsequently, using PP2A as the RG, RT-qPCR analysis showed that the expression level of most genes associated with carotenoid biosynthesis was extremely significantly up-regulated in sweet pepper seedlings under salt and drought stress. Specifically, violoxanthin deepoxidase (VDE) was significantly up-regulated by more than 481- and 36-fold under salt and drought stress, respectively; lycopene epsilon cyclase (LCYE) was significantly up-regulated by more than 840- and 23-fold under salt and drought stress, respectively. This study contributes to a more comprehensive understanding of the carotenoid biosynthesis pathway serving as a major source of retrograde signals in pepper subjected to different abiotic stresses.

Phyto-nutraceutical promise of Brassica vegetables in post-genomic era: a comprehensive review

MAIN CONCLUSION

Brassica vegetables are one of the possible solutions to tackle the emerging human diseases and malnutrition due to their rich content of phyto-nutraceutaical compounds. The genomics enabled tools have facilitated the elucidation of molecular regulation, mapping of genes/QTLs governing nutraceutical compounds, and development of nutrient-rich Brassica vegetables. The enriched food products or foods as whole termed as functional foods are intended to provide health benefits. The 2500 year old Hippocratic phrase 'let thy food be thy medicine and thy medicine be thy food' remained in anonymity due to lack of sufficient evidence. However, today, we are facing reappraisal of healthy nutritious functional foods in battling diseases. In this context, the Brassica vegetables represent the most extensively investigated class of functional foods. An optimal consumption of Brassica vegetables is associated with lowering the risks of several types of cancer, chronic diseases, cardiovascular disease, and help in autism. In the post-genomic era, the integration of genetic and neoteric omics tools like transcriptomics, metabolomics, and proteomics have illuminated the downstream genetic mechanisms governing functional food value of Brassica vegetables. In this review, we have summarized in brief the phyto-nutraceutical profile and their functionality in Brassica vegetables. This review also highlights the progress made in identification of candidate genes/QTLs for accumulation of bioactive compounds in Brassica vegetables. We summarize the molecular regulation of major phytochemicals and breeding triumphs in delivering multifunctional Brassica vegetables.

Identifying molecular targets for modulating carotenoid accumulation in rice grains

Carotenoids are potential antioxidants offering extensive human health benefits including protection against chronic diseases. Augmenting the supply of health-benefiting compounds/metabolites through dietary supplements is the most sustainable way for a healthy life. Our study compares the traditional rice cultivar Kavuni and the white rice variety ASD 16. RNA-Seq analysis was carried out in the maturing panicles of Kavuni, which are enriched with antioxidants such as the therapeutic carotenoid lutein, polyphenols, and anthocyanins, along with "ASD 16", a popularly eaten white rice variety, to elucidate the molecular networks regulating accumulation of health benefiting compounds. Systematic analysis of transcriptome data identified preferential up-regulation of carotenoid precursors (OsDXS, OsGGPS) and key carotenoid biosynthetic genes (OsPSY1, OsZ-ISO) in the maturing grains of Kavuni. Our study also identified enhanced expression of OsLYC-E, OsCYP97A, and OsCYP97C transcripts involved in the alpha-carotenoid biosynthetic pathway and thereby leading to elevated lutein content in the grains of Kavuni. Kavuni grains showed preferential down-regulation of negative regulators of carotenoid metabolism viz., AP2 and HY5 and preferential up-regulation of positive modulators of carotenoid metabolism viz., Orange, OsDjB7, and OsSET29, thus creating a favorable molecular framework for carotenoid accumulation. Our study has unearthed valuable gene control points for precise manipulation of carotenoid profiles through CRISPR-based gene editing in rice grains. Perturbation of carotenoid biosynthesis holds unprecedented potential for the rapid development of the next generation of 'Golden rice'.

Characterization of lycopene β-cyclase from Dunaliella bardawil for enhanced β-carotene production and salt tolerance

Dunaliella can accumulate more β-carotene (10 % or even more of the dry weight of cells) than any other species. Lycopene β-cyclase (LcyB) is the key enzyme in the catalysis of lycopene to β-carotene. In the present research, we used Escherichia coli BL21 (DE3) as host to construct two different types of engineering bacteria, one expressing the D. bardawil LcyB and the other expressing the orthologue Erwinia uredovora crtY. The catalytic ability of LcyB and CrtY were evaluated by comparing the β-carotene yields of the two E. coli BL21(DE3) strains, whose salt tolerance was simultaneously compared by cultivated them under different NaCl concentrations (1 %, 2 %, and 4 %). We also interfered with the LcyB gene to investigate the effect of LcyB in D. bardawil. Results displayed that the β-carotene yield of the LcyB-transformant significantly increased by about 48 % compared with the crtY-transformant. Additionally, LcyB was verified to be able to enhance the salt tolerance of E. coli BL21 (DE3). It is concluded that D. bardawil LcyB not only has better catalytic ability but also is able to confer salt tolerance to cells. Interfering D. bardawil LcyB induced the low expression of LcyB and the changes of growth and carotenoids metabolism in D. bardawil.

Novel Insights into Pigment Composition and Molecular Mechanisms Governing Flower Coloration in Rose Cultivars Exhibiting Diverse Petal Hues

The pigmentation of various components leads to different colors of roses. However, the intricate molecular machinery and metabolic pathways underlying rose pigmentation remain largely unexplored. In this study, we determined that pink and black-red petals contain abundant anthocyanins, reaching concentrations of 800 μg/g and 1400 μg/g, respectively, significantly surpassing those in white and yellow petals. We identified 22 key anthocyanin components, predominantly cyanidin, pelargonidin, delphinidin, peonidin, and petunidin, which were preferentially enriched in pink and black-red petals. Additionally, we confirmed the presence of five carotenoid species-lutein, zeaxanthin, ζ-carotene, α-carotene, and β-carotene-with zeaxanthin and carotenoids notably accumulating in yellow petals at significantly higher levels compared with other colors. Furthermore, RNA-seq and qRT-PCR analyses revealed the association between pigment accumulation and the expression patterns of genes involved in anthocyanin and carotenoid biosynthesis pathways. Through promoter core element prediction and transcriptional metabolic co-expression analyses, we found that the MYB transcription factor likely positively modulates the expressions of key biosynthetic genes such as CHS, F3'H, and DFR, while the NAC transcription factor enhances the transcriptional activities of PSY, ZISO, and LYCB. Overall, this study explores the components of flower color, unravels the synthesis of anthocyanins and carotenoids, identifies regulatory factors, and highlights the prospects of rose breeding.

Integrated metabolome and transcriptome analysis provides clues to fruit color formation of yellow, orange, and red bell pepper

Fruit color is a crucial trait for bell pepper. To investigate the mechanism of color formation, three bell pepper lines with different color (yellow, orange and red) were used as materials to conduct comprehensive targeted metabolomic and transcriptomic analyses. During the process of fruit development, 54 carotenoids metabolites were discovered, exhibiting unique accumulation patterns and notable variety specificity. The types and content of carotenoids in orange fruit (OM) were notably greater compared to the other two varieties. Red pigment (capsanthin and capsorubin) was specifically enriched in red fruit (RM), and yellow pigment (lutein and zeaxanthin) is the highest in yellow fruit (YM) and OM. Five modules positively correlated with carotenoid accumulation and one negative module was determined by weighted gene co-expression network analysis (WGCNA). Additionally, transcription factors (TFs) and hub genes related to carotenoid synthesis were predicted. By elucidating the regulation of 7 key carotenoid metabolites by 14 critical genes and 5 key TFs, we constructed a comprehensive carotenoid biosynthesis metabolic network that comprehensively explains the pigment changes observed in green and mature pepper fruit. Overall, the results not only provide important insights into carotenoid synthesis pathway, but also lay a solid base for revealing the mechanism of bell pepper color transformation.

Current and future perspectives for enhancing our understanding of the evolution of plant metabolism

The special issue 'The evolution of plant metabolism' has brought together original research, reviews and opinions that cover various aspects from the full breath of plant metabolism including its interaction with the environment including other species. Here, we briefly summarize these efforts and attempts to extract a consensus opinion of the best manner in which to tackle this subject both now and in the future. This article is part of the theme issue 'The evolution of plant metabolism'.

Conserved carotenoid pigmentation in reproductive organs of Charophyceae

Sexual reproduction in Charophyceae abounds in complex traits. Their gametangia develop as intricate structures, with oogonia spirally surrounded by envelope cells and richly pigmented antheridia. The red-probably protectant-pigmentation of antheridia is conserved across Charophyceae. Chara tomentosa is, however, unique in exhibiting this pigmentation and also in vegetative tissue. Here, we investigated the two sympatric species, C. tomentosa and Chara baltica, and compared their molecular chassis for pigmentation. Using reversed phase C30 high performance liquid chromatography (RP-C30-HPLC), we uncover that the major pigments are β-carotene, δ-carotene and γ-carotene; using headspace solid-phase microextraction coupled to gas chromatography equipped with a mass spectrometer (HS-SPME-GC-MS), we pinpoint that the unusually large carotenoid pool in C. tomentosa gives rise to diverse volatile apocarotenoids, including abundant 6-methyl-5-hepten-2-one. Based on transcriptome analyses, we uncover signatures of the unique biology of Charophycaee and genes for pigment production, including monocyclized carotenoids. The rich carotenoid pool probably serves as a substrate for diverse carotenoid-derived metabolites, signified not only by (i) the volatile apocarotenoids we detected but (ii) the high expression of a gene coding for a cytochrome P450 enzyme related to land plant proteins involved in the biosynthesis of carotenoid-derived hormones. Overall, our data shed light on a key protection strategy of sexual reproduction in the widespread group of macroalgae. The genetic underpinnings of this are shared across hundreds of millions of years of plant and algal evolution. This article is part of the theme issue 'The evolution of plant metabolism'.

Carotenoid composition and sequestration in cassava (Manihot esculentum Crantz) roots

Cassava (Manihot esculentum Crantz) is a staple food source for many developing countries. Its edible roots are high in starch but lack micronutrients such as β-carotene. In the present study, analysis of pedigree breeding populations has led to the identification of cassava accessions with enhanced β-carotene contents up to 40 μg/g DW. This represents 0.2% of the Recommended Daily Allowance (RDA) for vitamin A. The β-branch of the carotenoid pathway predominates in cassava roots, with dominant levels of β-carotene followed by other minor epoxides of β-ring derived carotenoids. Metabolomic analysis revealed that steady state levels of intermediary metabolism were not altered by the formation of carotenoids, similar to starch and carbohydrate levels. Apocarotenoids appeared to be independent of their carotenoid precursors. Lipidomic analysis provided evidence of a significant positive correlation between carotenoid and lipid content, in particular plastid specific galactolipids. Proteomic analysis of isolated amyloplasts identified the majority of proteins associated with translation and carbohydrate/starch biosynthesis (e.g. glucose-1-phosphate adenylyltransferase). No carotenoid related proteins were detected even in the highest carotenoid containing lines. Carotenoids were associated with fractions typically annotated as plastoglobuli and plastid membranes (particularly the envelope). Proteomic analysis confirmed these structures apart from plastoglobuli, thus potentially amyloplast structures may not contain classical plastoglobuli structures.

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.

Decoding the Impact of a Bacterial Strain of Micrococcus luteus on Arabidopsis Growth and Stress Tolerance

Microbes produce various bioactive metabolites that can influence plant growth and stress tolerance. In this study, a plant growth-promoting rhizobacterium (PGPR), strain S14, was identified as Micrococcus luteus (designated as MlS14) using de novo whole-genome assembly. The MlS14 genome revealed major gene clusters for the synthesis of indole-3-acetic acid (IAA), terpenoids, and carotenoids. MlS14 produced significant amounts of IAA, and its volatile organic compounds (VOCs), specifically terpenoids, exhibited antifungal activity, suppressing the growth of pathogenic fungi. The presence of yellow pigment in the bacterial colony indicated carotenoid production. Treatment with MlS14 activated the expression of β-glucuronidase (GUS) driven by a promoter containing auxin-responsive elements. The application of MlS14 reshaped the root architecture of Arabidopsis seedlings, causing shorter primary roots, increased lateral root growth, and longer, denser root hairs; these characteristics are typically controlled by elevated exogenous IAA levels. MlS14 positively regulated seedling growth by enhancing photosynthesis, activating antioxidant enzymes, and promoting the production of secondary metabolites with reactive oxygen species (ROS) scavenging activity. Pretreatment with MlS14 reduced H2O2 and malondialdehyde (MDA) levels in seedlings under drought and heat stress, resulting in greater fresh weight during the post-stress period. Additionally, exposure to MlS14 stabilized chlorophyll content and growth rate in seedlings under salt stress. MlS14 transcriptionally upregulated genes involved in antioxidant defense and photosynthesis. Furthermore, genes linked to various hormone signaling pathways, such as abscisic acid (ABA), auxin, jasmonic acid (JA), and salicylic acid (SA), displayed increased expression levels, with those involved in ABA synthesis, using carotenoids as precursors, being the most highly induced. Furthermore, MlS14 treatment increased the expression of several transcription factors associated with stress responses, with DREB2A showing the highest level of induction. In conclusion, MlS14 played significant roles in promoting plant growth and stress tolerance. Metabolites such as IAA and carotenoids may function as positive regulators of plant metabolism and hormone signaling pathways essential for growth and adaptation to abiotic stress.

Multi-omics analysis provides insights into the mechanism underlying fruit color formation in Capsicum

Fruit color is a crucial attribute of fruit quality in peppers (Capsicum spp.). However, few studies have focused on the mechanism of color formation in immature pepper fruits. In this study, the light-yellow color observed in immature CSJ009 fruits compared to CSJ010 could be attributed to decreased chlorophyll and carotenoid pigments. Through integrated analysis of the transcriptome and metabolome of CSJ009 and CSJ010, we identified 23,930 differentially expressed genes (DEGs) and 345 differentially accumulated metabolites (DAMs). Furthermore, integrated analysis revealed a strong correlation between the HCT-like gene and metabolite MWS0178 (chlorogenic acid). Paraffin section assay revealed that the epidermal cells of immature CSJ010 fruits exhibited a more compact arrangement with significantly greater length than those of CSJ009. Quantitative determination of carotenoids showed that lutein emerged as the predominant carotenoid in immature pepper fruits. Additionally, missense mutation of LCYB2 is likely to lead to a decrease in β-carotene content in immature CSJ009 fruits, whereas CCS may directly catalyze the conversion of lycopene to β-carotene in mature fruits. The null mutation in CCS promoted the biosynthesis of β,ϵ-branch carotenoids leading to lutein being the most abundant carotenoid found in orange CSJ010 fruits. These findings provide important insights into the mechanism underlying color formation in pepper fruits and establish a foundation for the further exploration of color-related genes.

Mild osmotic stress offers photoprotection in Chlamydomonas reinhardtii under high light

The exposure of autotrophs to high light intensities significantly impacts their photosynthetic performance. When combined with unpredictable climate changes, the lethality of these effects is exacerbated and, often surpassing the organisms' threshold for tolerance. In this regard, our study centres on examining the mitigating effects of mild osmotic stress induced by 2% Polyethylene Glycol (PEG) in conjunction with high-light conditions, using Chlamydomonas reinhardtii as a model system. Cells were cultivated under low PEG-induced osmotic stress at various light intensities, and their responses were analyzed through biochemical and biophysical approaches. Remarkably, cells grown under lower PEG concentrations exhibited superior growth, increased biomass, and enhanced photosynthetic efficiency under high light compared to non-PEG-treated cells. Surprisingly, their non-photochemical quenching (NPQ) levels were lower, indicating the operation of a distinct photoprotective mechanism in PEG-grown samples. The PEG-grown cells demonstrated higher chlorophyll content but lower carotenoid content, supporting the NPQ data. Circular dichroism analysis suggested that the macro-organization of super-complexes was minimally disrupted in PEG-grown samples, even under high light. This was further supported by Blue native PAGE, which showed greater stability of the super-complexes in PEG-grown cells, implying heightened stability in pigment-protein interactions. Immunoblot analysis revealed minimal differences in core reaction center proteins between PEG-grown and non-PEG cells. Notably, this protective mechanism was absent in the cell wall-deficient mutant CC503. We propose that the partial photoprotection observed is attributed to the PEG shielding the cell wall. This result holds promise for enhancing algal biomass production under natural environmental conditions influenced by fluctuating light intensity.

DcMYB62, a transcription factor from carrot, enhanced cadmium tolerance of Arabidopsis by inducing the accumulation of carotenoids and hydrogen sulfide

Cadmium (Cd) is a significant heavy metal contaminant within the environment, carrying a notable level of toxicity that presents a substantial hazard to both plant and human. Carrot (Daucus carota), a significant root vegetable crop globally, have evolved multiple transcriptional regulatory mechanisms to cope with Cd stress, with a crucial involvement of the myeloblastosis (MYB) transcription factor. In this study, the DcMYB62 gene encoding 288 amino acids, localized in the nucleus and demonstrated transcription activation property, was isolated from carrot (cv. 'Kuroda'). There was a positive relationship observed between the levels of DcMYB62 expression and the accumulation patterns of carotenoids in two distinct carrot cultivars. Further investigation revealed that the expression of DcMYB62 improved Cd tolerance of Arabidopsis by increasing seed germination rate, root length, and overall survival rate. The levels of carotenoids in DcMYB62 transgenic Arabidopsis surpassed those in wild type, accompanied by elevated expression levels of 15-cis-phytoene desaturase, zeta-carotene desaturase, and carotenoid isomerase. Meanwhile, the heterologous expression of DcMYB62 promoted the biosynthesis of abscisic acid (ABA) and hydrogen sulfide (H2S), which in turn suppressed the formation of hydrogen peroxide and superoxide anion, while also stimulating stomatal closure. Furthermore, the heterologous expression of DcMYB62 increased the transcription of genes associated with heavy metal resistance in Arabidopsis, notably nicotianamine synthase. Overall, this study contributes to understanding how DcMYB62 promote Cd stress resistance of plants by regulating the biosynthesis pathways of carotenoids, ABA, and H2S, which offers valuable insights into the regulatory mechanism connecting DcMYBs with Cd stress response of carrot.

Overexpressing CsPSY1 Gene of Tea Plant, Encoding a Phytoene Synthase, Improves α-Carotene and β-Carotene Contents in Carrot

Tea plants (Camellia sinensis (L.) O. Kuntze) belong to Theaceae family, in the section Thea. Tea plants are widely distributed in subtropical and tropical regions in the word. α-carotene and β-carotene in the tea leaves belong to carotenoids, which are associated with the aroma and color of the tea. Phytoene synthase (PSY) is a rate-limiting enzyme in carotenoids biosynthesis. We identified three CsPSY genes in 'Shuchazao', named CsPSY1, CsPSY2, and CsPSY3. Structural analysis of three CsPSY genes showed that CsPSY1 had a longer intro structure. The cis-acting elements of CsPSYs promoter were mainly associated with light-responsiveness, abiotic stress-responsiveness, and hormone-responsiveness. CsPSY1 exhibited expression in all tissues of the tea plants, whereas CsPSY2 and CsPSY3 were trace expression levels in all tissues. The positive expression of CsPSY1 under hormonal and abiotic stresses suggested its role in plant development and defense responses. The amino acid sequence of CsPSY1 was highly conserved in eight tea cultivars. The recombinant vector pCAMBIA1301-CsPSY1 was constructed to stabilize the overexpression of CsPSY1 in carrot. The contents of α-carotene and β-carotene in transgenic carrot callus were significantly increased. This study provides a foundational basis for further research on the function of CsPSYs and carotenoids accumulation in tea plants.

Examining Carotenoid Metabolism Regulation and Its Role in Flower Color Variation in Brassica rapa L

Carotenoids are vital organic pigments that determine the color of flowers, roots, and fruits in plants, imparting them yellow, orange, and red hues. This study comprehensively analyzes carotenoid accumulation in different tissues of the Brassica rapa mutant "YB1", which exhibits altered flower and root colors. Integrating physiological and biochemical assessments, transcriptome profiling, and quantitative metabolomics, we examined carotenoid accumulation in the flowers, roots, stems, and seeds of YB1 throughout its growth and development. The results indicated that carotenoids continued to accumulate in the roots and stems of YBI, especially in its cortex, throughout plant growth and development; however, the carotenoid levels in the petals decreased with progression of the flowering stage. In total, 54 carotenoid compounds were identified across tissues, with 30 being unique metabolites. Their levels correlated with the expression pattern of 22 differentially expressed genes related to carotenoid biosynthesis and degradation. Tissue-specific genes, including CCD8 and NCED in flowers and ZEP in the roots and stems, were identified as key regulators of color variations in different plant parts. Additionally, we identified genes in the seeds that regulated the conversion of carotenoids to abscisic acid. In conclusion, this study offers valuable insights into the regulation of carotenoid metabolism in B. rapa, which can guide the selection and breeding of carotenoid-rich varieties.

Efficient control of root-knot nematodes by expressing Bt nematicidal proteins in root leucoplasts

Root-knot nematodes (RKNs) are plant pests that infect the roots of host plants. Bacillus thuringiensis (Bt) nematicidal proteins exhibited toxicity to nematodes. However, the application of nematicidal proteins for plant protection is hampered by the lack of effective delivery systems in transgenic plants. In this study, we discovered the accumulation of leucoplasts (root plastids) in galls and RKN-induced giant cells. RKN infection causes the degradation of leucoplasts into small vesicle-like structures, which are responsible for delivering proteins to RKNs, as observed through confocal microscopy and immunoelectron microscopy. We showed that different-sized proteins from leucoplasts could be taken up by Meloidogyne incognita female. To further explore the potential applications of leucoplasts, we introduced the Bt crystal protein Cry5Ba2 into tobacco and tomato leucoplasts by fusing it with a transit peptide. The transgenic plants showed significant resistance to RKNs. Intriguingly, RKN females preferentially took up Cry5Ba2 protein when delivered through plastids rather than the cytosol. The decrease in progeny was positively correlated with the delivery efficiency of the nematicidal protein. In conclusion, this study offers new insights into the feeding behavior of RKNs and their ability to ingest leucoplast proteins, and demonstrates that root leucoplasts can be used for delivering nematicidal proteins, thereby offering a promising approach for nematode control.

Integrated Metabolomics and Transcriptomics Analyses Reveal the Regulatory Mechanisms of Anthocyanin and Carotenoid Accumulation in the Peel of Coffea arabica

The color of coffee fruits is influenced by several factors, including cultivar, ripening stage, and metabolite composition. However, the metabolic accumulation of pigments and the molecular mechanisms underlying peel coloration during the ripening process of Coffea arabica L. remain relatively understudied. In this study, UPLC-MS/MS-based metabolomics and RNA sequencing (RNA-seq)-based transcriptomics were integrated to investigate the accumulation of anthocyanins and carotenoids in the peel of Coffea arabica at different ripening stages: green peel (GP), green-yellow peel (GYRP), red peel (RP), and red-purple peel (RPP). This integration aimed at elucidating the molecular mechanisms associated with these changes. A total of ten anthocyanins, six carotenoids, and thirty-five xanthophylls were identified throughout the ripening process. The results demonstrated a gradual decrease in the total carotenoid content in the peel with fruit maturation, while anthocyanin content increased significantly. Notably, the accumulation of specific anthocyanins was closely associated with the transition of peel colors from green to red. Integrated metabolomics and transcriptomics analyses identified the GYRP stage as critical for this color transition. A weighted gene co-expression network analysis (WGCNA) revealed that enzyme-coding genes such as 3AT, BZ1, and lcyE, along with transcription factors including MYB, NAC, and bHLH, which interact with PHD and SET TR, may regulate the biosynthesis of anthocyanins and carotenoids, thereby influencing peel pigmentation. These findings provide valuable insights into the molecular mechanisms underlying the accumulation of anthocyanins and carotenoids in Coffea arabica peel during fruit maturation.

Chlorophyll a acts as a natural photosensitizer to drive nitrate reduction in nonphotosynthetic microorganisms

With the death and decomposition of widely distributed photosynthetic organisms, free natural pigments are often detected in surface water, sediment and soil. Whether free pigments can act as photosensitizers to drive biophotoelectrochemical metabolism in nonphotosynthetic microorganisms has not been reported. In this work, we provide direct evidence for the photoelectrophic relationship between extracellular chlorophyll a (Chl a) and nonphotosynthetic microorganisms. The results show that 10 μg of Chl a can produce significant photoelectrons (∼0.34 A/cm2) upon irradiation to drive nitrate reduction in Shewanella oneidensis. Chl a undergoes structural changes during the photoelectric process, thus the ability of Chl a to generate a photocurrent decreases gradually with increasing illumination time. These changes are greater in the presence of microorganisms than in the absence of microorganisms. Photoelectron transport from Chl a to S. oneidensis occurs through a direct pathway involving the cytochromes MtrA, MtrB, MtrC and CymA but not through an indirect pathway involving riboflavin. These findings reveal a novel photoelectrotrophic linkage between natural photosynthetic pigments and nonphototrophic microorganisms, which has important implications for the biogeochemical cycle of nitrogen in various natural environments where Chl a is distributed.

A novel C2H2-type zinc-finger transcription factor, CitZAT4, regulates ethylene-induced orange coloration in Satsuma mandarin flavedo (Citrus unshiu Marc.)

Ethylene treatment promotes orange coloration in the flavedo of Satsuma mandarin (Citrus unshiu Marc.) fruit, but the corresponding regulatory mechanism is still largely unknown. In this study, we identified a C2H2-type zinc-finger transcription factor, CitZAT4, the expression of which was markedly induced by ethylene. CitZAT4 directly binds to the CitPSY promoter and activates its expression, thereby promoting carotenoid biosynthesis. Transient expression in Satsuma mandarin fruit and stable transformation of citrus calli showed that overexpressing of CitZAT4 inhibited CitLCYE expression, thus inhibiting α-branch yellow carotenoid (lutein) biosynthesis. CitZAT4 overexpression also enhanced the transcript levels of CitLCYB, CitHYD, and CitNCED2, promoting β-branch orange carotenoid accumulation. Molecular biochemical assays, including yeast one-hybrid (Y1H), electrophoretic mobility shift (EMSA), chromatin immunoprecipitation quantitative polymerase chain reaction (ChIP-qPCR), and luciferase (LUC) assays, demonstrated that CitZAT4 directly binds to the promoters of its target genes and regulates their expression. An ethylene response factor, CitERF061, which is induced by ethylene signaling, was found to directly bound to the CitZAT4 promoter and induced its expression, thus positively regulating CitZAT4-mediated orange coloration in citrus fruit. Together, our findings reveal that a CitZAT4-mediated transcriptional cascade is driven by ethylene via CitERF061, linking ethylene signaling to carotenoid metabolism in promoting orange coloration in the flavedo of Satsuma mandarin fruit. The molecular regulatory mechanism revealed here represents a significant step toward developing strategies for improving the quality and economic efficiency of citrus crops.

Unbalanced Expression of Structural Genes in Carotenoid Pathway Contributes to the Flower Color Formation of the Osmanthus Cultivar 'Yanzhi Hong'

Carotenoids are important natural pigments that are responsible for the fruit and flower colors of many plants. The composition and content of carotenoid can greatly influence the color phenotype of plants. However, the regulatory mechanism underling the divergent behaviors of carotenoid accumulation, especially in flower, remains unclear. In this study, a new cultivar Osmanthus fragrans 'Yanzhi Hong' was used to study the regulation of carotenoid pigmentation in flower. Liquid chromatograph-mass spectrometer (LC-MS) analysis showed that β-carotene, phytoene, lycopene, γ-carotene, and lutein were the top five pigments enriched in the petals of 'Yanzhi Hong'. Through transcriptome analysis, we found that the expression of the structural genes in carotenoid pathway was imbalanced: most of the structural genes responsible for lycopene biosynthesis were highly expressed throughout the flower developmental stages, while those for lycopene metabolism kept at a relatively lower level. The downregulation of LYCE, especially at the late developmental stages, suppressed the conversion from lycopene to α-carotene but promoted the accumulation of β-carotene, which had great effect on the carotenoid composition of 'Yanzhi Hong'. Ethylene response factor (ERF), WRKY, basic helix-loop-helix (bHLH), v-myb avian myeloblastosis viral oncogene homolog (MYB), N-Acetylcysteine (NAC), auxin response factor (ARF), and other transcription factors (TFs) have participated in the flower color regulation of 'Yanzhi Hong', which formed co-expression networks with the structural genes and functioned in multiple links of the carotenoid pathway. The results suggested that the cyclization of lycopene is a key link in determining flower color. The modification of the related TFs will break the expression balance between the upstream and downstream genes and greatly influence the carotenoid profile in flowers, which can be further used for creating colorful plant germplasms.

Biosynthesis and Extraction of Chlorophyll, Carotenoids, Anthocyanins, and Betalaine In Vivo and In Vitro

As natural bioactive compounds, plant pigments play crucial roles not only in plant phenotype, growth, development, and adaptation to stress but also hold unique value in biotechnology, healthcare, and industrial applications. There is growing interest in the biosynthesis and acquisition of plant pigments. Thus, this paper explores emerging extraction methods of natural pigments and elucidates the biosynthesis pathways of four key plant pigments, chlorophylls, carotenoids, anthocyanins, and betalaine in vivo and in vitro. We comprehensively discuss the application of solvent, supercritical fluid [extraction], ultrasonic, and microwave-assisted extraction techniques, as well as introducing key enzymes, precursors, and synthetic pathways involved in pigment synthesis. δ-Aminolevulinic acid represents a pivotal initiating enzyme for chlorophyll synthesis, whereas isopentenylpyrophosphate, (IPP) and dimethylallyl pyrophosphate, (DMAPP) are closely associated with carotenoid biosynthesis. Phenylalanine and tyrosine are critical substances for anthocyanin and betalaine synthesis, respectively. Hence, crucial genes such as chlI, crtB, PGT8, CYP76AD1, and BvDODA can be employed for heterologous biosynthesis in vitro to meet the demand for increased plant pigment amount. As a pivotal determinant of plant coloration, an in-depth exploration into the high-quality acquisition of plant pigments can provide a basis for developing superior pigments and offer new insights into increasing pigment yield.

Extreme halophilic Archaea: Halobacterium salinarum carotenoids characterization and antioxidant properties

Important marine microorganisms are resources of renewable energy that may face global population growth and needs. The application of biomass metabolites, such as carotenoids and their derivatives, may solve some agro-food health problems. Herein, a new halophilic Archaea Halobacterium salinarum producing carotenoid was screened from a Tunisian solar Saltworks (Sfax). The identification of the carotenoid pigments was carried out using HPLC-MS/MS. The predominant pigments produced by this Halobacterium were bacterioruberin and its derivatives and the carotenoids production was found to be of 21.51 mg/mL. Moreover, the data revealed that the carotenoids extract exhibited a high antioxidant activity across four oxidizing assays. The present results suggested that carotenoids extracted from halophilic Archaea are interesting sources of natural antioxidants for future innovative applications in agro-food, cosmetic and health fields.

Metabolomic Analysis of Carotenoids Biosynthesis by Sphingopyxis sp. USTB-05

Carotenoids belonging to the class of tetraterpenoids have extensive applications in medicine, food, nutrition, cosmetics, and feed. Among them, lutein and zeaxanthin can prevent macular degeneration in the elderly, which is very important for protecting vision. Here, we introduce the first metabolomic analysis of Sphingopyxis sp. USTB-05, aiming to shed light on the biosynthesis of carotenoids. Sphingopyxis sp. USTB-05 has the complete methylerythritol 4-phosphate (MEP) pathway and carotenoid biosynthesis pathway, especially involved in the bioconversion of zeaxanthin, violaxanthin, and astaxanthin. Metabolomic profiling identified seven carotenes and six xanthophylls synthesized by Sphingopyxis sp. USTB-05. Zeaxanthin, in particular, was found to be the most abundant, with a content of 37.1 µg/g dry cells. Collectively, the results presented herein greatly enhance our understanding of Sphingopyxis sp. USTB-05 in carotenoids biosynthesis, and thus further accelerate its fundamental molecular investigations and biotechnological applications.

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.

De novo domestication: what about the weeds?

Most high-yielding crops are susceptible to abiotic and biotic stresses, making them particularly vulnerable to the potential effects of climate change. A possible alternative is to accelerate the domestication of wild plants that are already tolerant to harsh conditions and to increase their yields by methods such as gene editing. We foresee that crops' wild progenitors could potentially compete with the resulting de novo domesticated plants, reducing yields. To improve the recognition of weeds, we propose using gene editing techniques to introduce traits into de novo domesticated crops that will allow for visual recognition of the crops by weeding robots that have been trained by machine learning.

Unlocking nature's secrets: The pivotal role of WRKY transcription factors in plant flowering and fruit development

The WRKY transcription factor family is a key player in the regulatory mechanisms of flowering plants, significantly influencing both their biotic and abiotic response systems as well as being vital to numerous physiological and biological functions. Over the past two decades, the functionality of WRKY proteins has been the subject of extensive research in over 50 plant species, with a strong focus on their roles in responding to various stresses. Despite this extensive research, there remains a notable gap in comprehensive studies aimed at understanding how specific WRKY genes directly influence the timing of flowering and fruit development. This review offers an up-to-date look at WRKY family genes and provides insights into the key genes of WRKY to control flowering, enhance fruit ripening and secondary metabolism synthesis, and maintain fruit quality of various plants, including annuals, perennials, medicinal, and crop plants. The WRKY transcription factors serve as critical regulators within the transcriptional regulatory network, playing a crucial role in the precise enhancement of flowering processes. It is also involved in the up-regulation of fruit ripening was strongly demonstrated by combined transcriptomics and metabolomic investigation. Therefore, we speculated that the WRKY family is known to be a key regulator of flowering and fruiting in plants. This detailed insight will enable the identification of the series of molecular occurrences featuring WRKY proteins throughout the stages of flowering and fruiting.

Adaptive strategies to drought stress in grasses of the poaceae family under climate change: Physiological, genetic and molecular perspectives: A review

Drought stress is one of the most critical abiotic factors which negatively impacts on growth, productivity, and survival of plants. Grass species have an important role in the sustainable intensification of cropping systems. This review focus on the specific drought tolerance characteristics in grass species and application of prevalent classical and molecular methods for genetic improvement of them to drought stress. Generally, grass species adapt to drought stress by utilizing more than one strategy including of changes in the root growth, photosynthetic pigments, activation of antioxidant enzymes, and accumulation of compatible osmolytes. They also have other specific characteristics consisted of summer dormancy, drought recovery, and persistence, which lead to drought adaptation after prolonged drought. Studies on different grasses, indicated that most of above mentioned traits usually have positive correlation with drought tolerance. Also, high heritability has been reported for most of them in different grasses. Therefore, an effective index might be considering in identification of drought tolerance genotypes. Recently, high-throughput imaging phenotyping and advanced molecular techniques such as genotyping-by-sequencing (GBS), RNA sequencing, genome-wide association study, and genome editing help conventional breeding methods to increase the accuracy, selection efficiency, genetic gains, and speed of breeding programs for developing drought tolerant cultivars.

Linkage and association mapping in multi-parental populations reveal the genetic basis of carotenoid variation in maize kernels

Carotenoids are indispensable to plants and critical components of the human diet. The carotenoid metabolic pathway is conserved across plant species, but our understanding of the genetic basis of carotenoid variation remains limited for the seeds of most cereal crops. To address this issue, we systematically performed linkage and association mapping for eight carotenoid traits using six recombinant inbred line (RIL) populations. Single linkage mapping (SLM) and joint linkage mapping (JLM) identified 77 unique additive QTLs and 104 pairs of epistatic QTLs. Among these QTLs, we identified 22 overlapping hotspots of additive and epistatic loci, highlighting the important contributions of some QTLs to carotenoid levels through additive or epistatic mechanisms. A genome-wide association study based on all RILs detected 244 candidate genes significantly associated with carotenoid traits, 23 of which were annotated as carotenoid pathway genes. Effect comparisons suggested that a small number of loci linked to pathway genes have substantial effects on carotenoid variation in our tested populations, but many loci not associated with pathway genes also make important contributions to carotenoid variation. We identified ZmPTOX as the causal gene for a QTL hotspot (Q10/JLM10/GWAS019); this gene encodes a putative plastid terminal oxidase that produces plastoquinone-9 used by two enzymes in the carotenoid pathway. Natural variants in the promoter and second exon of ZmPTOX were found to alter carotenoid levels. This comprehensive assessment of the genetic mechanisms underlying carotenoid variation establishes a foundation for rewiring carotenoid metabolism and accumulation for efficient carotenoid biofortification.

A transcriptional cascade involving BBX22 and HY5 finely regulates both plant height and fruit pigmentation in citrus

Dwarfing is a pivotal agronomic trait affecting both yield and quality. Citrus species exhibit substantial variation in plant height, among which internode length is a core element. However, the molecular mechanism governing internode elongation remains unclear. Here, we unveiled that the transcriptional cascade consisting of B-BOX DOMAIN PROTEIN 22 (BBX22) and ELONGATED HYPOCOTYL 5 (HY5) finely tunes plant height and internode elongation in citrus. Loss-of-function mutations of BBX22 in an early-flowering citrus (Citrus hindsii "SJG") promoted internode elongation and reduced pigment accumulation, whereas ectopic expression of BBX22 in SJG, sweet orange (C. sinensis), pomelo (C. maxima) or heterologous expression of BBX22 in tomato (Solanum lycopersicum) significantly decreased internode length. Furthermore, exogenous application of gibberellin A3 (GA3) rescued the shortened internode and dwarf phenotype caused by BBX22 overexpression. Additional experiments revealed that BBX22 played a dual role in regulation internode elongation and pigmentation in citrus. On the one hand, it directly bound to and activated the expression of HY5, GA metabolism gene (GA2 OXIDASE 8, GA2ox8), carotenoid biosynthesis gene (PHYTOENE SYNTHASE 1, PSY1) and anthocyanin regulatory gene (Ruby1, a MYB DOMAIN PROTEIN). On the other hand, it acted as a cofactor of HY5, enhancing the ability of HY5 to regulate target genes expression. Together, our results reveal the critical role of the transcriptional cascade consisting of BBX22 and HY5 in controlling internode elongation and pigment accumulation in citrus. Unraveling the crosstalk regulatory mechanism between internode elongation and fruit pigmentation provides key genes for breeding of novel types with both dwarf and health-beneficial fortification in citrus.

Functionality of Reactive Oxygen Species (ROS) in Plants: Toxicity and Control in Poaceae Crops Exposed to Abiotic Stress

Agriculture and changing environmental conditions are closely related, as weather changes could adversely affect living organisms or regions of crop cultivation. Changing environmental conditions trigger different abiotic stresses, which ultimately cause the accumulation of reactive oxygen species (ROS) in plants. Common ROS production sites are the chloroplast, endoplasmic reticulum, plasma membrane, mitochondria, peroxisomes, etc. The imbalance in ROS production and ROS detoxification in plant cells leads to oxidative damage to biomolecules such as lipids, nucleic acids, and proteins. At low concentrations, ROS initiates signaling events related to development and adaptations to abiotic stress in plants by inducing signal transduction pathways. In plants, a stress signal is perceived by various receptors that induce a signal transduction pathway that activates numerous signaling networks, which disrupt gene expression, impair the diversity of kinase/phosphatase signaling cascades that manage the stress response in the plant, and result in changes in physiological responses under various stresses. ROS production also regulates ABA-dependent and ABA-independent pathways to mitigate drought stress. This review focuses on the common subcellular location of manufacturing, complex signaling mechanisms, and networks of ROS, with an emphasis on cellular effects and enzymatic and non-enzymatic antioxidant scavenging mechanisms of ROS in Poaceae crops against drought stress and how the manipulation of ROS regulates stress tolerance in plants. Understanding ROS systems in plants could help to create innovative strategies to evolve paths of cell protection against the negative effects of excessive ROS in attempts to improve crop productivity in adverse environments.

Jasmonic Acid and Salicylic Acid improved resistance against Spodoptera frugiperda Infestation in maize by modulating growth and regulating redox homeostasis

Exploring host plant resistance and elevating plant defense mechanisms through the application of exogenous elicitors stands as a promising strategy for integrated pest management. The fall armyworm, a pernicious menace to grain crops in tropical and subtropical regions, stands as a formidable threat due to its capacity for devastation and a wide-ranging spectrum of host plants. There is no literature regarding artificially induced resistance in maize against fall armyworm (Spodoptera frugiperda) by exogenous application of phytohormones. The present investigation was performed to evaluate the role of jasmonic acid (JA) and salicylic acid (SA) on two maize hybrids namely FH-1046 and YH-1898 against fall armyworm. Results showed that plant height, biomass and lengths, fresh and dry weight of root shoot which decreased with armyworm infestation improved with phytohormonal application. JA treatment resulted in a higher increase in all attributes as compared to SA treatment. Improvement in relative water contents, photosynthetic pigments and pronounced levels of phenol and proline accumulation were observed in infested plants after JA treatment. Infested plants recovered from oxidative stress as JA application activated and increased the antioxidant enzyme activity of superoxide dismutase, peroxidase and polyphenol oxidase activity in both FH-1046 and YH-1898 . The oxidative stress reduction in infested plants after JA treatment was also evident from a fair decrease in MDA and H2O2 in both varieties. The SA and JA mediated genes expression was studied and it was found that in FH1046 maize cultivar, JA dependent genes, particularly marker genes PR1 and Lox5 were highly expressed along with TPS10 and BBT12. Whereas SPI, WRKY28, ICS and PAL were shown to be activated upon SA application. Evidently, both JA and SA elicited a robust defensive response within the maize plants against the voracious S. frugiperda, which in consequence exerted a discernible influence over the pest's developmental trajectory and physiological dynamics. A decrease in detoxification enzyme activity of the insects was observed after feeding on treated plants. Moreover, it was recorded that the survival and weight gain of FAW feeding on phytohormone treated maize plants also decelerated. In conclusion, FH-1046 was found to be more tolerant than YH-1898 against fall armyworm infestation and 1 mM JA was more effective than 1 mM SA for alleviation of fall armyworm stress. Therefore, it was inferred that phytohormones regulated redox homeostasis to circumvent oxidative damage and mediate essential metabolic events in maize under stress. To our current understanding, this study is the very first presentation of induced resistance in maize against S. frugiperda with the phytohormonal application (JA and SA).