Fruit Color Research Articles

Agronomic, Biochemical, and Physiological Responses to Magnesium (Mg) Application in Tomato (Solanum lycopersicum L.) under Greenhouse Conditions

Magnesium fertilization positively impacts various physiological processes in plants, leading to increased yield and fruit quality. In the present study, we determined the effects of the foliar application of magnesium on the yield, fruit quality, fruit biochemical content, and enzyme activity of tomato plants. The study was performed in a plastic greenhouse. The study evaluated magnesium sulfate application through drip irrigation at a single dose of 0.005 kg m2 and foliar application at rates of 0%, 0.25%, 0.5%, and 0.75%. As a consequence, the highest average fruit weight was obtained with the foliar application of 0.50% Mg. In terms of the fruit color’s a* value, the best results were again obtained with the application of 0.50% Mg. Mg applications proportionally increased the leaf chlorophyll content. Similarly, the highest leaf Mg content, the leaf relative water content, the fruits’ malic acid content, and the best fruit juice pH value were determined with the application of 0.75%. On the other hand, the application of 0.25% Mg produced the best results on the leaves’ K, Ca, and Na content, as well as in the fruits’ ascorbic acid content. Significant differences were not found in terms of the effects of the treatments on antioxidant activity, total protein amount, and enzyme activity. The application of 0.50% Mg contributed to the fruit color; 0.75% Mg application contributed to the chlorophyll, pH, and malic acid content; and the application of 0.25% Mg contributed to an increase in ascorbic acid. In conclusion, for greenhouse tomato production, a foliar application of 0.50% Mg is recommended to achieve larger, red-colored fruits. A 0.75% Mg application is suggested for increasing the chlorophyll content, lowering fruit juice pH, and enhancing malic acid content in fruits. A 0.25% Mg application is recommended to increase ascorbic acid content in fruits.

Genome-Wide Identification and Expression Analysis of GST Genes during Light-Induced Anthocyanin Biosynthesis in Mango (Mangifera indica L.).

Anthocyanins are important secondary metabolites contributing to the red coloration of fruits, the biosynthesis of which is significantly affected by light. Glutathione S-transferases (GSTs) play critical roles in the transport of anthocyanins from the cytosol to the vacuole. Despite their importance, GST genes in mango have not been extensively characterized. In this study, 62 mango GST genes were identified and further divided into six subfamilies. MiGSTs displayed high similarity in their exon/intron structure and motif and domain composition within the same subfamilies. The mango genome harbored eleven pairs of segmental gene duplications and ten sets of tandemly duplicated genes. Orthologous analysis identified twenty-nine, seven, thirty-four, and nineteen pairs of orthologous genes among mango MiGST genes and their counterparts in Arabidopsis, rice, citrus, and bayberry, respectively. Tissue-specific expression profiling highlighted tissue-specific expression patterns for MiGST genes. RNA-seq and qPCR analyses revealed elevated expression levels of seven MiGSTs including MiDHAR1, MiGSTU7, MiGSTU13, MiGSTU21, MiGSTF3, MiGSTF8, and MiGSTF9 during light-induced anthocyanin accumulation in mango. This study establishes a comprehensive genetic framework of MiGSTs in mango fruit and their potential roles in regulating anthocyanin accumulation, which is helpful in developing GST-derived molecular markers and speeding up the process of breeding new red-colored mango cultivars.

The underlying molecular mechanisms of hormonal regulation of fruit color in fruit-bearing plants.

Fruit color is a key feature of fruit quality, primarily influenced by anthocyanin or carotenoid accumulation or chlorophyll degradation. Adapting the pigment content is crucial to improve the fruit's nutritional and commercial value. Genetic factors along with other environmental components (i.e., light, temperature, nutrition, etc.) regulate fruit coloration. The fruit coloration process is influenced by plant hormones, which alsoplay a vital role in various physiological and biochemical metabolic processes. Additionally, phytohormones play a role in the regulation of a highly conserved transcription factor complex, called MBW (MYB-bHLH-WD40). The MBW complex, which consists of myeloblastosis (MYB), basic helix-loop-helix (bHLH), and WD40 repeat (WDR) proteins, coordinates the expression of downstream structural genes associated with anthocyanin formation. In fruit production, the application of plant hormones may be important for promoting coloration. However, concerns such as improper concentration or application time must be addressed. This article explores the molecular processes underlying pigment formation and how they are influenced by various plant hormones. The ABA, jasmonate, and brassinosteroid increase anthocyanin and carotenoid formation, but ethylene, auxin, cytokinin, and gibberellin have positive as well as negative effects on anthocyanin formation. This article establishes the necessary groundwork for future studies into the molecular mechanisms of plant hormones regulating fruit color, ultimately aiding in their effective and scientific application towards fruit coloration.

Morphological Diversity of F1 Ornamental Chili Generation from Single Cross Hybridization

Ornamental chilli (Capsicum annuum L.) belongs to the Solanaceae family and is highly popular for its aesthetic value. Ornamental chilli plants are edible, with attractive plant architecture and fruit shapes, as well as varying levels of spiciness. The most preferred traits in ornamental chilli plants include compact size (suitable for potted plants), diverse and unique fruit shapes and colors, and upright fruit orientation. This study aims to investigate the morphological diversity in the F1 generation resulting from a single cross-hybridization between two ornamental chilli varieties, namely the Medusa Pepper, known for its compact growth habit, and the Black Pearl Pepper, characterized by purple-coloured fruits and leaves. Analysis of the qualitative data shows that the F1 generation shares a high degree of morphological similarity with the female parent, Black Pearl Pepper, with a similarity value exceeding 75%, while it exhibits no significant resemblance to the male parent, Medusa Pepper, with a similarity value of 0%. The F1 generation from the single cross demonstrates limited morphological variation, with all observed traits being largely influenced by dominant characteristics, including fruit color, plant habit, and leaf color.

Characterization of Litchi Genotypes Based on Flowering and Fruit Characters

Twenty genotypes of litchi were selected from three district of Uttar Pradesh viz., Khushinagar, Gorakhpur and Deoria, and assessed based on traits related to fruit and flowering during 2023 and 2024 with following three replications. The flower disc colour was light yellow for all genotypes. Shahi took the longest (26 days) to flower, while GG-2 took the lowest (20.75 days). Panicle length ranged from a minimum of 38.95 cm in genotype DP-2 to a maximum of 48.20 cm in genotype KD-2. Panicles with maximum width of 30.34 cm and a minimum width of 19.98 cm were produced by the genotype KS-1 and GC-2, respectively. Eleven genotypes showed red colour, whereas nine genotypes showed the colour of crimson fruit. The genotype DP-2 (11.84) had the fewest fruits per cluster, whereas genotype DB-2 (14.03) had the most fruits per cluster. Fruit lengths varied, with GC-1 having the longest at 38.44 mm and DP-2 having the shortest at 34.26 mm. With a fruit diameter of 33.13 mm, the genotype GC-1 displayed the highest size, while DP-2 displayed the smallest (30.11 mm). Fruit weight varied with DB-2 having the highest weight (23.38 g) and DP-2 having the lowest (20.52 g). Genotype DP-2 had the lowest aril weight (13.43 g) and GP-2 had the greatest aril weight (15.28 g). Total soluble solids (TSS) varied by genotype; genotype KT-1 displayed the highest TSS (19.99 °Brix) and genotype DT-2 the lowest (18.40 °Brix). Based on a quick review of the data, China (0.51 %) had the highest titratable acidity, and KS-1 (0.34 %) had the lowest. The longest seeds (23.66 mm) were found in fruit of genotype GP-2, whilst the shortest seeds (21.17 mm) were found in genotype DP-2. Analogously, genotype DT-1 exhibited the smallest seed breadth, measuring 11.94 mm, whereas genotype DB-2 demonstrated the biggest seed breadth, measuring 13.88 mm. Genotypes GC-1 had the lowest seed weights (3.24 and 3240 g), while DB-2 and DP-1 had the highest seed and test weights (4.15 and 4150 g). The genotype DB-2 produced big fruit with more number of fruit per cluster. This genotype can be promoted for further evaluation.

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.

A Flowering Morphological Investigation, Fruit Fatty Acids, and Mineral Elements Dynamic Changes of Idesia polycarpa Maxim.

Idesia polycarpa Maxim is a high-value species of fruit oil with edible, abundant linoleic acid and polyphenols. Idesia polycarpa is described as a dioecious species, and the flowers are male; female and bisexual flowers are produced on separate plants. In order to explore the flower types of Idesia polycarpa, the morphology of its flowers and inflorescence were investigated in this study. The flower and inflorescence types, the diameter, and the flowering sequencing in male and female inflorescence were determined. We also detected the length, width, and fresh weight of leaves, shoots, and female inflorescence, as well as the length and fresh weight of the petiole during the development. Additionally, we compared the length, width, the length/width ratio, and the flowering density between 5- and 7-year-old female trees. The phenological period observation of Idesia polycarpa showed that the development process can be roughly divided into 12 stages, including bud burst, leaf expansion, inflorescence growth, initial flowering, full flowering, flower decline, initial fruiting, fruit enlargement, fruit color change, fruit ripening, post-ripening of fruit, and leaf fall periods. Furthermore, four elites' fruit determined the oil content and the composition of fatty acid content during the development. The dynamic of fatty acids contents, the palrnitic acid, palmitoleic acid, stearic acid, oleic acid, and linolenic acid contents were detected during the fruit development of four elites. Moreover, the mineral elements content of fruit of four elites during development were determined. The patterns of vegetative and reproductive growth in young dioecious trees of Idesia polycarpa provided the theoretical basis for artificial pruning and training.

Anti-Inflammatory and Anticancer Effects of Anthocyanins in In Vitro and In Vivo Studies.

Anthocyanins, a class of flavonoid compounds responsible for the vibrant colors of many fruits and vegetables, have received considerable attention in recent years due to their potential health benefits. This review, focusing on evidence from both in vitro and in vivo studies, provides a comprehensive overview of the current state of knowledge regarding the health-promoting properties of anthocyanins. The chemical structure and diversity of anthocyanins, their bioavailability, and their mechanisms of action at the cellular and molecular level are examined. Research on the antioxidant, anti-inflammatory, anticancer, and neuroprotective effects of anthocyanins is critically reviewed. Special emphasis is placed on the role of anthocyanins in the prevention and treatment of chronic diseases such as cardiovascular diseases, diabetes, and neurodegenerative diseases. This review also discusses the challenges of translating in vitro findings to in vivo and highlights the importance of considering dose, bioavailability, and metabolism when assessing the therapeutic potential of anthocyanins. This review concludes with the identification of gaps in current research and suggestions for future directions for anthocyanin studies, including the need for more long-term clinical trials and investigations into potential synergistic effects with other phytochemicals. This comprehensive analysis highlights the promising role of anthocyanins in promoting human health and provides valuable insights for researchers, health professionals, and the nutraceutical industry. This study provides new insights, as it comprehensively investigates the dual anti-inflammatory and anticancer effects of anthocyanins in both in vitro and in vivo models. By uncovering the biological properties of anthocyanins from a variety of natural sources, this research not only expands our knowledge of the action of these compounds at the cellular level, but also enhances their clinical relevance through in vivo validation. Furthermore, the innovative use of anthocyanins may lead to important advances in their therapeutic application in the future.

Study on Maturity Indices and Effect of Growing Substrates on Seed Germination of Litsea glutinosa

Aim: Litsea glutinosa is a multipurpose, fast-growing tree widely exploited due to its multipurpose utilisation. Species reported low seed viability, hence generally propagated through vegetative methods. We studied the maturity indices of fruits and seeds to determine the optimal collection stage. Studied the effect of different growing substrates and Gibberellic acid (GA3) treatment on the germination percent (GP), mean germination time (MGT), germination value (GV), peak value (PV), and germination index (GI). Study Design: Study was conducted at Forest Tree Seed Laboratory, ICFRE-FRI. The change in fruit colour from green, dark brown purple, and dark blue stages was compared with the seed parameters, germination percent, mean germination time, germination value, etc. to obtain the most suitable stage for fruit and seed maturity. Seed germination experiment was conducted in Complete Randomized Design with four replications of 25 seeds for each treatment. Seeds were sown directly on different germination substrates, such as filter paper, sand, and vermiculite, without treatment and also with 0.05% GA3 pretreatment. Seeds were kept in the seed germinator at 25±1ºC with a 24-hour photoperiod and high relative humidity (RH > 90%). Results: The highest germination rate was observed in vermiculite with GA3 soaking . i.e., 80±3.26%, followed by vermiculite 68±8.64%. The lowest germination percent of 5±4.08% was observed in seeds plated on filter paper with GA3 soaking. No germination was recorded in the seeds plated on the filter paper. Conclusion: Most suitable germination medium to maximise the germination of L. glutinosa seed is vermiculite. Furthermore, the pretreatment of seeds in GA3 (0.05%) for 24 hours and sowing in vermiculite improves overall performance with respect to GP, MGT, GV, PV, and GI. In the context of maturity indices, the dark blue stage with a moisture content of around 50% is the right stage for the collection of seeds of the species. This stage is characterised by high GP, GV, and low MGT values as compared to other growth stages.

A telomere‐to‐telomere haplotype‐resolved genome of white‐fruited strawberry reveals the complexity of fruit colour formation of cultivated strawberry

A telomere‐to‐telomere haplotype‐resolved genome of white‐fruited strawberry reveals the complexity of fruit colour formation of cultivated strawberry

Influence of Combined Supplemental Lighting and Nutrient Solution Concentration on Fruit Production and Quality of Cherry Tomato

We conducted an analysis on the combined effects of two light conditions (L1: greenhouse natural lighting; L2: greenhouse natural lighting plus supplemental lighting (SL)) and three nutrient solution concentrations (EC, NS1: 3.2 dS/m; NS2: 3.7 dS/m; NS3: 4.2 dS/m) on the growth, fruit production, and quality of two cherry tomato cultivars with different fruit coloring (‘Baiyu’ and ‘Qianxi’). The plants subjected to NS2 exhibited enhanced growth, photosynthetic parameters, and fruit production. The utilization of SL further enhanced stem diameter, leaf number, and single fruit weight, resulting in higher fruit weight per plant in ‘Baiyu’, which was not observed in ‘Qianxi’. The growth, fruit size, and fruit weight of both cultivars cultivated under NS3 conditions were suppressed, while these fruits exhibited elevated levels of total soluble solids (TSS), soluble sugars, vitamin C, polyphenols, fructose, glucose, sucrose, citric acid, and carotenoids. These levels were further enhanced by SL treatment. The improvement of fruit quality through the application of SL was found to be cultivar and EC dependent. In ‘Baiyu’, SL at NS1 significantly enhanced the accumulation of fruit water, minerals (N, P, K, Ca, and Mg), TSS, vitamin C, fructose, sucrose, and carotenoids. However, this effect was not observed in ‘Qianxi’. The combination of SL and EC 4.2 dS/m (NS3) generally contributes to the enhancement of fruit quality, while SL and EC 3.7 dS/m can ensure consistent fruit production. The yellowish-white fruit cultivar exhibited higher levels of soluble sugars, vitamin C, and polyphenols under L2NS3 conditions compared to the red fruit cultivar, whereas the carotenoid content showed an opposite trend. The findings are anticipated to establish a theoretical foundation for the consistent annual cultivation of cherry tomatoes in protected horticultural settings.

Mapping and transcriptomic profiling reveal that the KNAT6 gene is involved in the dark green peel colour of mature pumpkin fruit (Cucurbita maxima L.).

We identified a 580bp deletion of CmaKNAT6 coding region influences peel colour of mature Cucurbita maxima fruit. Peel colour is an important agronomic characteristic affecting commodity quality in Cucurbit plants. Genetic mapping of fruit peel colour promotes molecular breeding and provides an important basis for understanding the regulatory mechanism in Cucurbit plants. In the present study, the Cucurbita maxima inbred line '9-6' which has a grey peel colour and 'U3-3-44' which has a dark green peel colour in the mature fruit stage, were used as plant materials. At 5-40days after pollination (DAP), the contents of chlorophyll a, chlorophyll b, total chlorophyll and carotenoids in the 'U3-3-44' peels were significantly greater than those in the '9-6' peels. In the epicarp of the '9-6' mature fruit, the presence of nonpigmented cell layers and few chloroplasts in each cell in the pigmented layers were observed. Six generations derived by crossing '9-6' and 'U3-3-44' were constructed, and the dark green peel was found to be controlled by a single dominant locus, which was named CmaMg (mature green peel). Through bulked-segregant analysis sequencing (BSA-seq) and insertion-deletion (InDel) markers, CmaMg was mapped to a region of approximately 449.51kb on chromosome 11 using 177 F2 individuals. Additionally, 1703 F2 plants were used for fine mapping to compress the candidate interval to a region of 32.34kb. Five coding genes were in this region, and CmaCh11G000900 was identified as a promising candidate gene according to the reported function, sequence alignment, and expression analyses. CmaCh11G000900 (CmaKNAT6) encodes the homeobox protein knotted-1-like 6 and contains 4 conserved domains. CmaKNAT6 of '9-6' had a 580bp deletion, leading to premature transcriptional termination. The expression of CmaKNAT6 tended to increase sharply during the early fruit development stage but decrease gradually during the late period of fruit development. Allelic diversity analysis of pumpkin germplasm resources indicated that the 580bp deletion in the of CmaKNAT6 coding region was associated with peel colour. Subcellular localization analysis indicated that CmaKNAT6 is a nuclear protein. Transcriptomic analysis of the inbred lines '9-6' and 'U3-3-44' indicated that genes involved in chlorophyll biosynthesis were more enriched in 'U3-3-44' than in '9-6'. Additionally, the expression of transcription factor genes that positively regulate chlorophyll synthesis and light signal transduction pathways was upregulated in 'U3-3-44'. These results lay a foundation for further studies on the genetic mechanism underlying peel colour and for optimizing peel colour-based breeding strategies for C. maxima.

CONVECTIVE DRYING OF CHOKEBERRY CV. “VIKING” AND MODELING OF DRYING KINETICS

In this study, the effects of drying air temperatures (50, 60, 70, and 80°C) and velocities (0.5, 0.8, and 1.2 m/s) on chokeberry quality during convective drying were evaluated. The drying time decreased significantly with increasing drying air temperatures and velocities, from 2265 minutes at 50°C to 195 minutes at 80°C, and from 360 minutes at 0.5 m/s to 240 minutes at 1.2 m/s at 70°C. Higher drying air temperatures and velocities also enhanced the fruit color quality. The best antioxidant activity, anthocyanin, and phenolic content were achieved at 70°C with dryin air velocities between 0.5 m/s and 1.2 m/s. The Midilli et al. model provided the best fit for the drying kinetics, with high accuracy (R²≥0.9978, χ²≤0.0003, RMSE≤0.0161).

How life became colourful: colour vision, aposematism, sexual selection, flowers, and fruits.

Plants and animals are often adorned with potentially conspicuous colours (e.g. red, yellow, orange, blue, purple). These include the dazzling colours of fruits and flowers, the brilliant warning colours of frogs, snakes, and invertebrates, and the spectacular sexually selected colours of insects, fish, birds, and lizards. Such signals are often thought to utilize pre-existing sensitivities in the receiver's visual systems. This raises the question: what was the initial function of conspicuous colouration and colour vision? Here, we review the origins of colour vision, fruit, flowers, and aposematic and sexually selected colouration. We find that aposematic colouration is widely distributed across animals but relatively young, evolving only in the last ~150 million years (Myr). Sexually selected colouration in animals appears confined to arthropods and chordates, and is also relatively young (generally <100 Myr). Colourful flowers likely evolved ~200 million years ago (Mya), whereas colourful fruits/seeds likely evolved ~300 Mya. Colour vision (sensu lato) appears to be substantially older, and likely originated ~400-500 Mya in both arthropods and chordates. Thus, colour vision may have evolved long before extant lineages with fruit, flowers, aposematism, and sexual colour signals. We also find that there appears to have been an explosion of colour within the last ~100 Myr, including >200 origins of aposematic colouration across nine animal phyla and >100 origins of sexually selected colouration among arthropods and chordates.

Transcriptome Analysis Identified PyNAC42 as a Positive Regulator of Anthocyanin Biosynthesis Induced by Nitrogen Deficiency in Pear (Pyrus spp.)

Anthocyanins are important secondary metabolites in plants, which contribute to fruit color and nutritional value. Anthocyanins can be regulated by environmental factors such as light, low temperature, water conditions, and nutrition limitations. Nitrogen (N) is an essential macroelement for plant development, its deficiency as a kind of nutrition limitation often induces anthocyanin accumulation in many plants. However, there is a lack of reports regarding the effect of nitrogen deficiency on anthocyanin biosynthesis in pears. In this study, we found that N deficiency resulted in anthocyanin accumulation in pear callus and upregulated the expression of anthocyanin biosynthesis pathway structural genes (PyPAL, PyCHS, PyCHI, PyF3H, PyDFR, PyANS, and PyUFGT) and key regulatory factors (PyMYB10, PyMYB114, and PybHLH3). Through analysis of transcriptome data of treated pear callus and RT-qPCR assay, a differentially expressed gene PyNAC42 was identified as significantly induced by the N deficiency condition. Overexpression of PyNAC42 promoted anthocyanin accumulation in “Zaosu” pear peels. Additionally, dual luciferase assay and yeast one-hybrid assay demonstrated that PyNAC42 could not directly activate the expression of PyDFR, PyANS, and PyUFGT. Furthermore, yeast two-hybrid and pull-down assays confirmed that PyNAC42 interacted with PyMYB10 both in vivo and in vitro. Co-expression of PyNAC42 and PyMYB10 significantly enhanced anthocyanin accumulation in “Zaosu” pear peels. Dual luciferase assay showed that PyNAC42 significantly enhanced the activation of PyDFR, PyANS, and PyUFGT promoters by interacting with PyMYB10, which suggests that PyNAC42 can form the PyNAC42-PyMYB10 complex to regulate anthocyanin biosynthesis in pear. Thus, the molecular mechanism underlying anthocyanin biosynthesis induced by N deficiency is preliminarily elucidated. Our finding has expanded the regulatory network of anthocyanin biosynthesis and enhanced our understanding of the mechanisms underlying nutrient deficiency modulates anthocyanin biosynthesis in pear.

The dominant white color trait of the melon fruit rind is associated with epicuticular wax accumulation.

Microscopic analyses and chemical profiling demonstrate that the white rind phenotype in melon fruit is associated with the accumulation of n-alkanes, fatty alcohols, aldehydes and wax esters. Serving as an indicator of quality, the rind (or external) color of fruit directly affects consumer choice. A fruit's color is influenced by factors such as the levels of pigments and deposited epicuticular waxes. The latter produces a white-grayish coating often referred to as "wax bloom". Previous reports have suggested that some melon (Cucumis melo L.) accessions may produce wax blooms, where a dominant white rind color trait was genetically mapped to a major locus on chromosome 7 and suggested to be inherited as a single gene named Wi. We here provide the first direct evidence of the contribution of epicuticular waxes to the dominant white rind trait in melon fruit. Our light and electron microscopy and gas chromatography-mass spectrometry (GC-MS) comparative analysis of melon accessions with white or green rinds reveals that the rind of melon fruit is rich in epicuticular waxes. These waxes are composed of various biochemical classes, including fatty acids, fatty alcohols, aldehydes, fatty amides, n-alkanes, tocopherols, triterpenoids, and wax esters. We show that the dominant white rind phenotype in melon fruit is associated with increased accumulation of n-alkanes, fatty alcohols, aldehydes and wax esters, which are linked with the deposition of crystal-like wax platelets on their surfaces. Together, this study broadens the understanding of natural variation in an important quality trait of melon fruit and promotes the future identification of the causative gene for the dominant white rind trait.

Loss-of-function mutation in anthocyanidin reductase activates the anthocyanin synthesis pathway in strawberry

Fruit color substantially affects consumer preferences, with darker red strawberries being economically more valuable due to their higher anthocyanin content. However, the molecular basis for the dark red coloration remains unclear. Through screening of an ethyl methanesulfonate mutant library, we identified a rg418 mutant, that demonstrated anthocyanin accumulation during early fruit development stages. Furthermore, the ripening fruits of this mutant had higher anthocyanin content than wild-type (WT) fruits. An analysis of flavonoid content in WT and rg418 mutant fruits revealed substantial changes in metabolic fluxes, with the mutant exhibiting increased levels of anthocyanins and flavonols and decreased levels of proanthocyanidins. Bulked sergeant analysis sequencing indicated that the mutant gene was anthocyanidin reductase (ANR), a key gene in the proanthocyanidin synthesis pathway. Furthermore, transcriptome sequencing revealed the increased expression of MYB105 during the early development stage of mutant fruits, which promoted the expression of UFGT (UDP-glucose flavonoid 3-O-glucosyltransferase), a key gene involved in anthocyanin synthesis, thus substantially enhancing the anthocyanin content in the mutant fruits. Additionally, mutating ANR in a white-fruited strawberry variant (myb10 mutant) resulted in appealing pink-colored fruits, suggesting the diverse roles of ANR in fruit color regulation. Our study provides valuable theoretical insights for improving strawberry fruit color.

The Genome-Wide Identification of the Dihydroflavonol 4-Reductase (DFR) Gene Family and Its Expression Analysis in Different Fruit Coloring Stages of Strawberry.

Dihydroflavonol 4-reductase (DFR) significantly influences the modification of flower color. To explore the role of DFR in the synthesis of strawberry anthocyanins, in this study, we downloaded the CDS sequences of the DFR gene family from the Arabidopsis genome database TAIR; the DFR family of forest strawberry was compared; then, a functional domain screen was performed using NCBI; the selected strawberry DFR genes were analyzed; and the expression characteristics of the family members were studied by qRT-PCR. The results showed that there are 57 members of the DFR gene family in strawberry, which are mainly expressed in the cytoplasm and chloroplast; most of them are hydrophilic proteins; and the secondary structure of the protein is mainly composed of α-helices and random coils. The analysis revealed that FvDFR genes mostly contain light, hormone, abiotic stress, and meristem response elements. From the results of the qRT-PCR analysis, the relative expression of each member of the FvDFR gene was significantly different, which was expressed throughout the process of fruit coloring. Most genes had the highest expression levels in the full coloring stage (S4). The expression of FvDFR30, FvDFR54, and FvDFR56 during the S4 period was 8, 2.4, and 2.4 times higher than during the S1 period, indicating that the DFR gene plays a key role in regulating the fruit coloration of strawberry. In the strawberry genome, 57 members of the strawberry DFR gene family were identified. The higher the DFR gene expression, the higher the anthocyanin content, and the DFR gene may be the key gene in anthocyanin synthesis. Collectively, the DFR gene is closely related to fruit coloring, which lays a foundation for further exploring the function of the DFR gene family.

Genome-Wide Analysis of Fruit Color and Carotenoid Content in Capsicum Core Collection.

This study investigated carotenoid content and fruit color variation in 306 pepper accessions from diverse Capsicum species. Red-fruited accessions were predominant (245 accessions), followed by orange (35) and yellow (20). Carotenoid profiles varied significantly across accessions, with capsanthin showing the highest mean concentration (239.12 μg/g), followed by β-cryptoxanthin (63.70 μg/g) and zeaxanthin (63.25 μg/g). Total carotenoid content ranged from 7.09 to 2566.67 μg/g, emphasizing the diversity within the dataset. Correlation analysis revealed complex relationships between carotenoids, with strong positive correlations observed between total carotenoids and capsanthin (r = 0.94 ***), β-cryptoxanthin (r = 0.87 ***), and zeaxanthin (r = 0.84 ***). Principal component analysis (PCA) identified two distinct carotenoid groups, accounting for 67.6% of the total variance. A genome-wide association study (GWAS) identified 91 significant single nucleotide polymorphisms (SNPs) associated with fruit color (15 SNPs) and carotenoid content (76 SNPs). These SNPs were distributed across all chromosomes, with varying numbers on each. Among individual carotenoids, α-carotene was associated with 28 SNPs, while other carotenoids showed different numbers of associated SNPs. Candidate genes encoding diverse proteins were identified near significant SNPs, potentially contributing to fruit color variation and carotenoid accumulation. These included pentatricopeptide repeat-containing proteins, mitochondrial proton/calcium exchangers, E3 ubiquitin-protein ligase SINAT2, histone-lysine N-methyltransferase, sucrose synthase, and various enzymes involved in metabolic processes. Seven SNPs exhibited pleiotropic effects on multiple carotenoids, particularly β-cryptoxanthin and capsanthin. The findings of this study provide insights into the genetic architecture of carotenoid biosynthesis and fruit color in peppers, offering valuable resources for targeted breeding programs aimed at enhancing the nutritional and sensory attributes of pepper varieties.

The ERF transcription factor ZbERF3 promotes ethylene-induced anthocyanin biosynthesis in Zanthoxylum bungeanum

Ethylene regulates fruit ripening, and in Zanthoxylum bungeanum, fruit color deepened with increasing of ethylene during fruit ripening. However, the molecular mechanism of this physiological process was still unclear. In this study, through the combined analysis of transcriptome and metabolome, it was found that ethylene release was consistent with anthocyanin synthesis, and ethylene response factors (ERFs) were significantly related to anthocyanin biosynthesis during the fruit ripening of Z. bungeanum. Ethylene treatment significantly induced fruit coloration and promoted anthocyanin synthesis and the expression of ZbERF3. Furthermore, Yeast one-hybrid assays and Luciferase reporter assays demonstrated that ZbERF3 directly bound to the promoter of ZbMYB17 and transcriptionally activated its expression. What's more, it was demonstrated that ZbMYB17 directly bound to the promoter of ZbANS, promoting anthocyanin biosynthesis. Overall, this study revealed the mechanism of ERF and MYB synergistically regulating the coloration of Z. bungeanum fruit.