Mechanism Of Color Change Research Articles

Integrative transcriptome and whole-genome bisulfite sequencing analyses of a temperature-sensitive albino tea plant cultivar.

Green tea made from albino buds and leaves has a strong umami taste and aroma. The cultivar 'Zhonghuang 2' (ZH2, Camellia sinensis) is a natural mutant with young shoots that are yellow in spring and green or yellow-green in summer. However, the mechanism of leaf color change remains unclear. Here, we found that young shoots of ZH2 were yellow at low temperature (LT) and green at high temperature (HT), indicating that ZH2 is a temperature-sensitive cultivar. Transmission electron microscopy analysis showed that the grana in the chloroplasts of young shoots grown at LT were poorly stacked, which caused a lack of photoreactions and chlorophyll. RNA-seq results showed 1279 genes differentially expressed in the young shoots grown at LT compared with those at HT, including genes related to cytochrome synthesis, chloroplast development, photosynthesis, and DNA methylation. A whole-genome bisulfite sequencing assay revealed that the dynamics of DNA methylation levels in the CG, CHG, and CHH contexts decreased under LT, and the change was most obvious in the CHH context. Furthermore, 72 genes showed significant changes in both expression and DNA methylation levels, and most of them were related to cytochrome synthesis, chloroplast development, photosynthesis, transcription factors, and signaling pathways. These results demonstrate that DNA methylation is involved in the LT-regulated albino processes of ZH2. Changes in DNA methylation levels were associated with changes in gene expression levels, affecting the structure and function of chloroplasts, which may have a phenotypic impact on shoot and leaf color.

Comparative Transcriptome and Metabolome Profiling Reveal Mechanisms of Red Leaf Color Fading in Populus × euramericana cv. 'Zhonghuahongye'.

Anthocyanins are among the flavonoids that serve as the principal pigments affecting the color of plants. During leaf growth, the leaf color of 'Zhonghuahongye' gradually changes from copper-brown to yellow-green. At present, the mechanism of color change at different stages has not yet been discovered. To find this, we compared the color phenotype, metabolome, and transcriptome of the three leaf stages. The results showed that the anthocyanin content of leaves decreased by 62.5% and the chlorophyll content increased by 204.35%, 69.23%, 155.56% and 60%, respectively. Differential metabolites and genes were enriched in the pathway related to the synthesis of 'Zhonghuahongye' flavonoids and anthocyanins and to the biosynthesis of secondary metabolites. Furthermore, 273 flavonoid metabolites were detected, with a total of eight classes. DFR, FLS and ANS downstream of anthocyanin synthesis may be the key structural genes in reducing anthocyanin synthesis and accumulation in the green leaf of 'Zhonghuahongye'. The results of multi-omics analysis showed that the formation of color was primarily affected by anthocyanin regulation and its related synthesis-affected genes. This study preliminarily analyzed the green regression gene and metabolic changes in 'Zhonghuahongye' red leaves and constitutes a reference for the molecular breeding of 'Zhonghuahongye' red leaves.

Mechanisms for leaf color changes in Osmanthus fragrans ‘Ziyan Gongzhu’ using physiology, transcriptomics and metabolomics

BackgroundColor-leaved O. fragrans is a variety of Osmanthus fragrans, which has both the fragrance of Osmanthus and the color of color-leaved plants. However, the molecular mechanism of color change of color-leaved O. fragrans is not clear. In this study, we analyzed the regulatory mechanism of four different color leaves of ‘Ziyan Gongzhu’ through physiological, transcriptome and metabolome levels.ResultsFirstly, we measured the leaf pigments content and leaf chromatic parameters for correlation analysis, indicating a significant correlation between them. Overall, the content of chlorophyll a + b is low and the content of anthocyanin is high in T1 and T2 leaves, along with low expression of chlorophyll synthesis genes (HEMA, CHLG, and CAO, etc.) and high expression of anthocyanin synthesis genes (F3H, F3’H, DFR and ANS, etc.), resulting purple red and light purple in T1 and T2 leaves, respectively. It was also found that the pigment closely related to the color leaves of ‘Ziyan Gongzhu’ was cyanidin. The content anthocyanins, may be regulated by two putative MYB activators (OfMYB3 and OfMYB4) and two putative MYB repressors (OfMYB1 and OfMYB2). In contrast, the content of chlorophyll a + b is high and the content of anthocyanin is low in T3 and T4 leaves, along with high expression of chlorophyll synthesis genes and low expression of anthocyanin synthesis genes, resulting yellow green and dark green in T3 and T4 leaves, respectively. And abnormal chloroplast development affects chlorophyll content in T1, T2, and T3 leaves. Although the content of carotenoids first dropped in T2 leaves, it then rapidly accumulated in T4 leaves, in sync with the increase in the expression of genes related to carotenoid biosynthesis (ZDS, LHYB, and ZEP, for example). Analysis of photosynthetic, carbohydrate and hormone-related differentially abundant metabolites (DAMs) and DEGs found that they may participate in the regulation of leaf color change of ‘Ziyan Gongzhu’ by affecting pigment synthesis.ConclusionOur results pave the way for a comprehensive knowledge of the regulatory processes governing leaf color in ‘Ziyan Gongzhu’ and identify possible genes for application regarding molecular colored-leaf cultivar breeding.

Metabolomic and microbiomic insights into color changes during the sweating process in Dipsacus asper.

Sweating is one of the most important primary processing methods of Chinese medicinal materials. Dipsacus asper is a typical representative of sweating treatment that is recommended by the Chinese Pharmacopoeia. The color change of the fracture surface of the root is the prominent feature of sweating treatment. However, few studies have focused on the mechanism of color change during sweating treatment. In this study, widely targeted metabolomics and ITS high-throughput sequencing technologies were applied to detect metabolites and microbial structure and diversity in the root of D. asper during sweating treatment. A total of 667 metabolites, including 36 downregulated and 78 upregulated metabolites, were identified in D. asper following sweating treatment. The significantly differential metabolites were divided into 12 classes, including terpenoids and phenolic acids. Moreover, all the differential terpenoids were upregulated and 20 phenolic acids showed a significant change after sweating treatment. In addition, microbial community diversity and richness increased following sweating treatment. The composition of microbial communities revealed that the relative abundances of Ascomycota and Basidiomycota significantly changed after sweating treatment. Correlation analysis revealed that Ascomycota (Fusarium sp., Macrophomina sp., Ilyonectria sp., Memnoniella sp., Penicillium sp., Cyphellophora sp., Neocosmospora sp., unclassified_f_Nectriaceae, and unclassified_o_Saccharomycetales) and Basidiomycota (Armillaria sp.) were associated with the content of terpenoids (6-deoxycatalpol and laciniatoside III) and phenolic acids (3-(4-hydroxyphenyl)-propionic acid, ethyl caffeate, 4-O-glucosyl-4-hydroxybenzoic acid, 2-acetyl-3-hydroxyphenyl-1-O-glucoside, 4-O-glucosyl-3,4-dihydroxybenzyl alcohol, 3-O-feruloylquinic acid, 3,4-O-dicaffeoylquinic acid methyl ester, O-anisic acid, and coniferyl alcohol). We speculate that the Ascomycota and Basidiomycota affect the content of terpenoids and phenolic acids, resulting in color change during sweating treatment in D. asper. This study provides a foundation for analyzing the mechanism involved in the processing of Chinese medicinal materials.

The non-enzymatic browning of pine bark during thermal treatment: Color and chemical changes, color kinetics and insights into mechanisms

Thermal treatment is an essential modification method for agroforestry biomass, and it causes the most intuitive change in agroforestry biomass, a color change. But there is still a lack of color change mechanism due to the complexity of the thermal behavior. In this work, Masson pine bark was thermally treated at 80–200 °C for 3–9 h. The monosaccharide compositions of untreated pine bark and the content of cellulose, hemicellulose, lignin, total phenolic, and total sugar during thermal treatment were determined to investigate the substrates and pathways triggering non-enzymatic browning reactions. UPLC-HESI-MS/MS, TG, SEM, FTIR, XRD, and color analysis were performed to track the association between chemical changes, color changes and pyrolysis properties. The results showed that the colorimetric parameters L*, a*, and b* values decreased with temperature and time, while ΔE* values increased. The color changes in L*, a*, and b* values were well described by the combined color kinetic model, with corresponding zero-order activation energies of 8.06 kJ/mol, 2.79 kJ/mol, and 3.5 kJ/mol and first-order activation energies of 11.45 kJ/mol, 18.55 kJ/mol, and 18.66 kJ/mol, respectively. And the predictive ability of the combined color kinetic model and the reliability of kinetic parameters was verified at an extended temperature of 220 °C. Furthermore, chemical changes confirmed that the formation of colored compounds (such as 5-hydroxymethylfurfural, furfural, and (+)-Procyanidin B2) by the non-enzymatic browning reactions and the degradation of the colored polymers existed in thermal treatment. Together, insights into the non-enzymatic browning reaction mechanisms and color kinetics provided a scientific basis for controlling color quality and valorized application of agroforestry wastes.

Integrated Transcriptome and Biochemical Analysis Provides New Insights into the Leaf Color Change in Acer fabri

Acer fabri is a widely distributed ornamental tree with colorful leaves and high ornamental value. Its young leaves change from red to red and green until turning fully green. To understand the mechanism of leaf color change, transcriptome sequencing and pigment content determination were performed in three stages during the leaf color change of A. fabri. In total, 53,550 genes, including 838 transcription factors (TFs), were identified by transcriptome sequencing. In addition, the results of orthogonal partial least squares-discriminant analysis (OPLS-DA) of three pigments in the three stages of leaf color development suggested that carotenoids played a major role in the process of leaf color change from red to red-green, whereas anthocyanins played an important role in the process of leaf color change from red to green. Based on weighted gene co-expression network analysis (WGCNA), Af0034384 (HSFB2A), Af0051627 (NMT1), and Af0052541 (THY-1) were selected as hub genes from characteristic modules with significant correlation between carotenoids and anthocyanins. The results of gene network regulation maps and real-time fluorescence quantitative PCR (qRT-PCR) showed that Af0010511 (NAC100) upregulated the expression of Af0034384 (HSFB2A), leading to an increase in carotenoid content and the gradual greening of leaves during the transition from red to green. However, during the transition from red to green leaves, Af0033232 (NAC83) and Af0049421 (WRKY24) downregulated the expression of Af0051627 (NMT1) and Af0052541 (THY-1), respectively, leading to a decrease in anthocyanin content and the complete greening of leaves. These results could provide new ideas for studying the molecular mechanism of leaf color change in A. fabri and other species.

Study on the color-changing mechanism and law of visual formaldehyde sensing system based on hyperbranched polyamines

This study focuses on addressing the limitations associated with most chemical derivatization methods commonly used for formaldehyde detection. These methods often suffer from prolonged derivative times (≥30 min) and complex procedures, which hinder their ability to meet the requirements of real-time and accurate sensing. In this research, a novel formaldehyde indicator system based on hyperbranched polyamine molecule was developed, and its mechanism and principles of color change were investigated. The findings revealed that hyperbranched polyamine molecule effectively reacts with formaldehyde, leading to a reduction in electron cloud density in the amine group N and subsequently causing a decrease in pH value. This reaction enables the visualization of formaldehyde detection through changes in the indicator spectrum. Moreover, the spectral variation pattern exhibits a strong linear correlation with the formaldehyde concentration when the PAMAM concentration is optimized. The detection limit of this method was determined to be 1.8 ppm. Notably, the reaction between PAMAM and formaldehyde is almost instantaneous, the color change is insensitive to temperature, and the method demonstrates high selectivity. Overall, this research contributes to the advancement of real-time formaldehyde monitoring technology and provides insights for future developments in this field.

Research progress in conductive polymer-based electrochromic fabrics

Conductive polymer-based electrochromic fabrics show promising applications in new intelligent displays, flexible smart wearables, and military camouflage, thanks to their flexibility, light weight, high degree of controllability, and wide range of color change. However, despite these advantages, electrochromic textiles that rely on conductive polymers face several limitations, such as discomfort during use, instability in structure, and issues with the continuous production technology of electrochromic fibers. These factors hinder their further development. To address these limitations and promote the industrialization of conductive polymer-based electrochromic fabrics, this paper provides a comprehensive analysis that covers various aspects of electrochromic devices, including device structure, color-change mechanisms, electrochromic materials, application of electrochromic textiles, and the advantages and disadvantages of commonly used conductive polymers in electrochromic fabrics. By exploring these aspects, a better understanding of the structure and performance of conductive polymer-based electrochromic fabrics can be achieved, leading to a more effective promotion of their industrialization. Moreover, progress in the research of conductive polymer-based electrochromic fabrics is systematically reviewed from the structural design perspective, both domestically and internationally. Finally, the challenges that conductive polymer-based electrochromic fabrics currently face are discussed, and their future development trends are presented.

Synergistic luminescence effect and high-pressure optical properties of CsPbBr2Cl@EuMOFs nanocomposites.

Metal-organic frameworks (MOFs) are a class of highly porous materials that have garnered significant attention in the field of optoelectronics due to their exceptional properties. In this study, CsPbBr2Cl@EuMOFs nanocomposites were synthesized using a two-step method. The fluorescence evolution of the CsPbBr2Cl@EuMOFs was investigated under high pressure, revealing a synergistic luminescence effect between CsPbBr2Cl and Eu3+. The study found that the synergistic luminescence of CsPbBr2Cl@EuMOFs remains stable even under high pressure, and there is no energy transfer among different luminous centers. These findings provide a meaningful case for future research on nanocomposites with multiple luminescent centers. Additionally, CsPbBr2Cl@EuMOFs exhibit a sensitive color-changing mechanism under high pressure, making them a promising candidate for pressure calibration via the color change of the MOF materials.

The phased chromosome-scale genome of yellowhorn sheds light on the mechanism of petal color change

Yellowhorn (Xanthoceras sorbifolium), especially its varieties, is the red petal yellowhorn (X. sorbifolium var. purpurea), an important tree species with great ornamental value, and its flower petals change color throughout the flowering period. In this study, we mainly focused on the mechanism of the petal color change with transcriptomics and metabolomics data. A phased chromosome-scale assembly of the red petal yellowhorn genome was generated using the PacBio high-fidelity reads, Illumina short reads, and Phase genomics Proximo Hi-C data. The final de novo assembly yielded 533.67 Mb with a contig N50 of 5.42 Mb, and 27 501 protein-coding genes were predicted. Notably, an alternate haplotig assembly was also obtained. Furthermore, a variation database for the alleles within the genome was constructed. Subsequently, the expression pattern of flower pigmentation-related genes and allelic expression imbalance events were investigated. Apart from 6 genes involved in the anthocyanin biosynthesis pathway regulated by the activation of 15 MYB-bHLH-WD40s, the increased expression of senescence-related gene 1 (SRG1) and 2-oxoglutarate-dependent dioxygenase (DIOX5) might also result in decreasing content of lutein and increasing abundance of (E/Z)-phytoene, cyanidin-3-O-rutinoside, and cyanidin-3-O-sambubioside. These changes in genes and metabolites were most likely related to the petal color change in red petal yellowhorn. This phased chromosome-scale genome assembly provides more accurate genomic information for future molecular breeding and facilitates allele function studies of the red petal yellowhorn.

Ontogenetic color change in the tail of blue-tailed skinks (Plestodion elegans).

Ontogenetic color change in animals is an interesting evolution-related phenomenon that has been studied by evolutionary biologists for decades. However, obtaining quantitative and continuous color measurements throughout the life cycle of animals is a challenge. To understand the rhythm of change in tail color and sexual dichromatism, we used a spectrometer to measure the tail color of blue-tailed skink (Plestiodon elegans) from birth to sexual maturity. Lab color space was selected due to its simplicity, fastness, and accuracy and depends on the visual sense of the observer for measuring the tail color of skinks. A strong relationship was observed between color indexes (values of L*, a*, b*) and growth time of skink. The luminance of tail color decreased from juveniles to adults in both sexes. Moreover, we observed differences in color rhythms between the sexes, which may be influenced by different behavioral strategies used by them. This study provides continuous measurements of change in tail color in skinks from juveniles to adults and offers insights into their sex-based differences. While this study does not provide direct evidence to explain the potential factors that drive dichromatism between the sexes of lizards, our finding could serve as a reference for future studies exploring possible mechanisms of ontogenetic color change in reptiles.

FsHemF is involved in the formation of yellow Forsythia leaves by regulating chlorophyll synthesis in response to light intensity

The leaves of Forsythia koreana ‘Suwon Gold’ are yellow under natural light condition and can revert to green when the light intensity is reduced. To understand the molecular mechanism of leaf color changes in response to light intensity, we compared the chlorophyll content and precursor content between yellow- and green-leaf Forsythia under shade and light-recovery conditions. We identified the conversion of coproporphyrin III (Coprogen III) to protoporphyrin IX (Proto IX) as the primary rate-limiting step of chlorophyll biosynthesis in yellow-leaf Forsythia. Further analysis of the activity of the enzymes that catalyze this step and the expression pattern of the chlorophyll biosynthesis-related genes under different light intensities revealed that the negatively regulated expression of FsHemF by light intensity was the major cause affecting the leaf color change in response to light intensity in yellow-leaf Forsythia. To further understand the cause of differential expression pattern of FsHemF in yellow- and green-leaf lines, we compared the coding sequence and promoter sequence of FsHemF between yellow- and green-leaf Forsythia. We found that one G-box light-responsive cis-element was absent in the promoter region of green-leaf lines. To investigate the functional role of FsHemF, we performed virus-induced gene silencing (VIGS) of FsHemF in green-leaf Forsythia, which leads to yellowing leaf veins, decreased chlorophyll b content, and inhibition of chlorophyll biosynthesis. The results will assist in elucidating the mechanism of yellow-leaf Forsythia in response to light intensity.

Metabolome analysis reveals flavonoid changes during the leaf color transition in Populus × euramericana 'Zhonghuahongye'.

To investigate the mechanism of leaf color change at different stages in Populus × euramericana 'Zhonghuahongye' ('Zhonghong' poplar). Leaf color phenotypes were determined and a metabolomic analysis was performed on leaves at three stages (R1, R2 and R3). The a*, C* and chromatic light values of the leaves decreased by 108.91%, 52.08% and 113.34%, while the brightness L values and chromatic b* values gradually increased by 36.01% and 13.94%, respectively. In the differential metabolite assay, 81 differentially expressed metabolites were detected in the R1 vs. R3 comparison, 45 were detected in the R1 vs. R2 comparison, and 75 were detected in the R2 vs. R3 comparison. Ten metabolites showed significant differences in all comparisons, which were mostly flavonoid metabolites. The metabolites that were upregulated in the three periods were cyanidin 3,5-O-diglucoside, delphinidin, and gallocatechin, with flavonoid metabolites accounting for the largest proportion and malvidin 3- O-galactoside as the primary downregulated metabolite. The color shift of red leaves from a bright purplish red to a brownish green was associated with the downregulation of malvidin 3-O-glucoside, cyanidin, naringenin, and dihydromyricetin. Here, we analyzed the expression of flavonoid metabolites in the leaves of 'Zhonghong' poplar at three stages and identified key metabolites closely related to leaf color change, providing an important genetic basis for the genetic improvement of this cultivar.

Combined whole transcriptome analysis and physical-chemical reveals the leaf color change mechanism of Ulmus pumila under heat stress

Ulmus pulima ‘ZhonghuaJinye’ (JY-elm) is a new variety of Ulmus genus with high landscape ecological benefits and golden leaves. However, the leaf color of JY-elm is significantly influenced by temperature, which changed from golden to white (albino) gradually under heat stress. Therefore, the present study explores the mechanism of JY-elm leaf color changes under high-temperature stress conditions. The photosynthetic pigment contents and related enzyme activities decreased significantly, leaf color changed from green to white, and the arrangement of palisade tissue was loose enough to disappear with abnormal thylakoid structures and fewer grana lamellae in JY-elm leaves under high-temperature stress. The photosynthetic parameters of JY-elm, Pn, Tr, and Cs decreased significantly with the increasing temperature, which caused plants to almost lose photosynthetic capacity. Further, the whole RNA-Seq profile was used to establish the ceRNA network, and the photosynthesis and chlorophyll metabolism pathways and related key regulated genes responses to heat stress were identified in this network. The results indicated that JY-elm leaf bleaching is irreversible damage at 37 °C, while plants are in a phase of resistance to high temperatures at 29 °C. This may be related to the damage to the chloroplast structure of elm under high temperature stress. This study revealed the mechanism of leaf color variation and response to heat stress in elm, and the established ceRNA network provided a basis for further research in the future.

Transcriptome Analysis Reveals the Central Role of the Transcription Factor MYB in Regulating Anthocyanin Accumulation in Economic Grape Species (Vitis vinifera)

To cultivate different grape varieties according to market needs, it is necessary to study the regulation mechanism of color changes in different development stages of grapes. In this study, RNA-sequencing (RNA-Seq) technology was used to compare and analyze the transcriptome data of four grape varieties at the same development stage. Among the annotated differential genes, the anthocyanin synthesis pathway in the flavonoid pathway was mainly studied. Further RT-qPCR analysis of key enzyme genes, in the flavonoid synthesis pathway of the anthocyanin metabolism pathway, showed that the MYB transcription factor family had binding sites at the start of the four enzyme genes. The relative expression of the MYB transcription factor and enzyme gene in the transcriptome data was verified by reverse transcription polymerase chain reaction. Subcellular localization and gene function verification of the transcription factor MYB2 confirmed its regulatory role in anthocyanins.

Optimal allyl isothiocyanate concentration on Botrytis cinerea during the postharvest storage of blackberries and mechanism of blackberry color changes at high concentration of allyl isothiocyanate

Botrytis cinerea is one of the most important postharvest pathogens causing economical loss in blackberry. To control B. cinerea effectively with safe agent, optimal allyl isothiocyanate (AITC) concentration was determined. Freshly harvested blackberries were placed in a plastic container and treated with AITC at 0, 0.5, 1, 2, 5, and 10 μL L-1 for 12 h at 4 °C, and then stored for 14 d at 4 °C and 80 % relative humidity. The B. cinerea incidence of AITC-treated blackberry samples after storage was lower than that of the control. Treatment with AITC at concentrations ≥ 5 μL L-1 resulted in a decrease in the total anthocyanin and phenolic contents, antioxidant activity, and surface color. The sucrose, glucose, and fructose levels decreased after treatment with 10 μL L-1 AITC, suggesting changed energy metabolism. Higher AITC concentrations (5 and 10 μL L-1) resulted in decreased levels of monogalactosyldiacylglycerol, digalactosyldiacylglycerol, and sulfoquinovosyldiacylglycerol. By contrast, lysophosphatidylethanolamine (LPE) and lysophosphatidylcholine (LPC) increased in the fruit treated with 5 and 10 μL L-1 AITC, indicating cell membranes damage related phospolipids. In summary, 2 μL L-1 AITC was the optimal concentration for blackberry treatment to reduce B. cinerea contamination and extend the fruit shelf-life. In addition, red color of blackberry correlated with LPC and phatidylcholine, which can serve good indicator of reduced cell membrane integrity. This is the first report of metabolomics-based study on controlling B. cinerea during blackberry postharvest storage using AITC.

Role of delphinidin-3-glucoside in the sepal blue color change among Hydrangea macrophylla cultivars

The sepals of Hydrangea macrophylla (H. macrophylla) are famous for their color changes under different cultivation conditions. Despite the structure of the blue complex in blue sepals has been confirmed by chemical and biological studies on hydrangea, the mechanism of sepal color change is still not completely understood. In fact, not all cultivars with pink–red sepal color have blue sepals in acidic soils with Al ions. To determine the key factors affecting the bluing capability of sepal color in H. macrophylla, nine cultivars with different bluing capability of sepal color were tested to investigate the effect of the contents of aluminum, copigments and anthocyanins in sepals on the change in sepal color in this research. The results showed that delphinidin-3-glucoside directly determines the content of the blue complexes in sepals. Moreover, the proportion of delphinidin-3-glucoside among all anthocyanins in sepals was a key factor determining the bluing capability of sepal color in H. macrophylla. Based on the further research, it was concluded that the bluing capability of sepal color was positively correlated with the proportion of delphinidin-3-glucoside among all the anthocyanins in sepals, which was positively regulated by the transcription ratio of F3’5’H to F3’H in all the tested cultivars. This study provides useful data for cultivation, breeding, and further research on the molecular mechanism of the bluing capability of sepal color in H. macrophylla.

Integrative Analysis of Metabolome and Transcriptome Reveals the Mechanism of Color Formation in Yellow-Fleshed Kiwifruit.

During the development of yellow-fleshed kiwifruit (Actinidia chinensis), the flesh appeared light pink at the initial stage, the pink faded at the fastest growth stage, and gradually changed into green. At the maturity stage, it showed bright yellow. In order to analyze the mechanism of flesh color change at the metabolic and gene transcription level, the relationship between color and changes of metabolites and key enzyme genes was studied. In this study, five time points (20 d, 58 d, 97 d, 136 d, and 175 d) of yellow-fleshed kiwifruit were used for flavonoid metabolites detection and transcriptome, and four time points (20 d, 97 d, 136 d, and 175 d) were used for targeted detection of carotenoids. Through the analysis of the content changes of flavonoid metabolites, it was found that the accumulation of pelargonidin and cyanidin and their respective anthocyanin derivatives was related to the pink flesh of young fruit, but not to delphinidin and its derivative anthocyanins. A total of 140 flavonoid compounds were detected in the flesh, among which anthocyanin and 76% of the flavonoid compounds had the highest content at 20 d, and began to decrease significantly at 58 d until 175 d, resulting in the pale-pink fading of the flesh. At the mature stage of fruit development (175 d), the degradation of chlorophyll and the increase of carotenoids jointly led to the change of flesh color from green to yellow, in addition to chlorophyll degradation. In kiwifruit flesh, 10 carotenoids were detected, with none of them being linear carotenoids. During the whole development process of kiwifruit, the content of β-carotene was always higher than that of α-carotene. In addition, β-cryptoxanthin was the most-accumulated pigment in the kiwifruit at 175 d. Through transcriptome analysis of kiwifruit flesh, seven key transcription factors for flavonoid biosynthesis and ten key transcription factors for carotenoid synthesis were screened. This study was the first to analyze the effect of flavonoid accumulation on the pink color of yellow-fleshed kiwifruit. The high proportion of β-cryptoxanthin in yellow-fleshed kiwifruit was preliminarily found. This provides information on metabolite accumulation for further revealing the pink color of yellow-fleshed kiwifruit, and also provides a new direction for the study of carotenoid biosynthesis and regulation in yellow-fleshed kiwifruit.

Regulatory mechanisms and metabolic changes of miRNA during leaf color change in the bud mutation branches of Acer pictum subsp. mono.

Acer pictum subsp. mono is a colorful tree species with considerable ornamental and economic value. However, little is known about the metabolism and regulatory mechanism of leaf color change in A. p. subsp. mono. To reveal the molecular mechanism of leaf color change in A. p. subsp. mono, the present study examined the bud mutation branches and compared the metabolites of the red leaves (AR) of the bud mutation branches of A. p. subsp. mono with those of the green leaves (AG) of the wild-type branches. It was found that the chlorophyll and carotenoids content of the red leaves decreased significantly, while anthocyanins, and various antioxidant enzymes increased significantly compared with the green leaves. The glycosides cyanidin, pelargonidin, malvidin, petunidin, delphinidin, and peonidin were detected in AR by liquid chromatography-mass spectrometry. The cyanidin glycosides increased, and cyanidin 3-O-glycoside was significantly upregulated. We analyzed the transcriptome and small RNA of A. p. subsp. mono leaves and detected 4061 differentially expressed mRNAs and 116 differentially expressed miRNAs. Through miRNA-mRNA association analysis, five differentially expressed modules were found; one miRNA targeted three genes, and four miRNAs targeted a single gene. Among them, miR160b, miR6300, and miR396g were found to be the key miRNAs regulating stable anthocyanin accumulation in A. p. subsp. mono leaves. By revealing the physiological response of leaf color change and the molecular regulatory mechanism of the miRNA, this study provides new insight into the molecular regulatory mechanism of leaf color change, thereby offering a foundation for future studies.

Ultra-performance liquid chromatography-quadrupole time-of-flight mass spectrometry-based metabolomics to clarify the mechanism of color change of saffron floral bio-residues.

Saffron floral bio-residues (SFB) are a valuable natural source of antioxidants and dyes that can contribute to the development of new food products and cosmetic products. Color change was usually observed during SFB storage, which may result in quality degradation of SFB or even cause potential hazard to human health. In order to clarify the mechanism of color change of SFB sample, the chemical differences among SFB samples stored under different conditions were analyzed using ultra-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry and chemometrics methods, from which differential flavonols and anthocyanins were screened and their kinetic variations during sample storage summarized. In addition, the color change of the SFB sample was digitalized using an electronic eye (E-eye), which was found to be related to the content of delphinidin-3,5-di-O-glucoside (DDG). Moreover, the degradation kinetic parameters of DDG under different storage conditions were studied. In conclusion, the variation of kaempferol-, isorhamnetin-, and quercetin-type flavonol, and delphinidin- and petunidin-type anthocyanin resulted in the color change of SFB sample, and anthocyanin was found more unstable than flavonol. PRACTICAL APPLICATION: Saffron floral bio-residues (SFB) are popular natural sources of antioxidants and colorants that can be used in food and cosmetic products. Color change usually occurs during SFB storage period. Clarifying the mechanism of the color change of SFB will help us to ensure the quality of SFB.