Variations in chlorophyll and carotenoid contents and expression of genes involved in pigment metabolism response to oleocellosis in citrus fruits

Integrating ATAC-seq and RNA-seq to reveal the dynamics of chromatin accessibility and gene expression in regulating aril coloration of Taxus mairei

Fruit coloration results from a complex process. Maire yew (Taxus mairei) is an evergreen tree with red, purple, and yellow fruits (arils). While significant progress has been made in understanding pigment biosynthesis in arils, the role of chromatin accessibility in color development remains less well understood. To gain deeper insights into the genetic and epigenetic factors involved, we employed RNA sequencing (RNA-seq) and assay for transposase-accessible chromatin sequencing (ATAC-seq). By integrating the results, we identified 723 differentially expressed genes (DEGs) with chromatin changes in P vs. R, including 312 up- and 411 down-regulated genes. In Y vs. R, we found 159 DEGs, with 97 up- and 62 down-regulated. KEGG enrichment analysis highlighted the flavonoid and carotenoid pathways as major contributors to color variation. When the arils turned purple, the expression levels of C4H, CHS, C3'H, F3'H, F3H, DFR, PSY, PDS, β-OHase, CYP97A3, and LUT1 were significantly up-regulated, while ZDS was down-regulated. The transition to yellow arils was characterized by the up-regulation of F3H, DFR, ZDS, CYP97A3, β-OHase, and LUT1, accompanied by the down-regulation of C4H, CHS, PSY, and PDS. Additionally, 27 transcription factors (TFs) were identified, including MYB, bHLH, and bZIP. These TFs may potentially influence variation in aril color by regulating downstream genes. In total, eight genes were selected for qRT-PCR validation, indicating the reliability of the transcriptome sequencing data. Our results provide in-depth information regarding the coloration of the arils in Maire yew. The study could provide insights for further genetic improvement in Taxus.

Evaluation of Chiral Pesticide Chlorbufam at the Enantiomeric Level: Absolute Configuration, Separation, Herbicidal Activity, and Degradation in Soil

Chlorbufam is a photosynthesis inhibitor chiral herbicide with a pair of enantiomers, which is rarely a concern. In this work, the optically pure enantiomers of chlorbufam were first synthesized and characterized, and the enantioselective herbicidal activity and mechanism were studied. Chlorbufam enantiomers showed significant differences in bioactivity against Echinochloa crus-galli and Abutilon theophrasti, and R-(+)-chlorbufam was identified as the most active against the targeted organisms with higher bioactivity of 3.95 and 1.71 times than S-(-)-chlorbufam. Chlorbufam enantiomers exerted herbicidal activity by inhibiting photosynthesis according to the results of the determination of photosynthetic pigment contents and molecular docking. Additionally, a novel HPLC-MS/MS method was successfully developed and validated for the detection of chlorbufam enantiomers and further applied for the enantioselective degradation study in soil. As a result, chlorbufam was satisfactory enantioseparated with a resolution of 2.37 on a Chiralpak IH column using the mobile phase of acetonitrile and water (60:40, v/v). Good linearity for chlorbufam enantiomers was obtained with correlation coefficients ≥0.9990, and the recovery ranged from 74.1 to 119% with relative standard deviations ≤10.9% at three spiked levels. The degradation behaviors of chlorbufam enantiomers were significantly different, and S-(-)-chlorbufam was preferentially degraded. The findings encouraged the application of enantiopure R-(+)-chlorbufam herbicide to reduce dosage rates, decrease environmental risks, and protect human health.

Effects of melatonin on inhibiting quality deterioration of postharvest water bamboo shoots

Water bamboo shoots (Zizania latifolia) is prone to quality deterioration during cold storage after harvest, which causes the decline of commodity value. Chlorophyll synthesis and lignin deposition are the major reasons for quality degradation. This paper studied the influence of exogenous melatonin (MT) on the cold storage quality of water bamboo shoots. MT treatment could delay the increase in skin browning, hardness and weight loss rate, inhibit chlorophyll synthesis and color change of water bamboo shoots, while maintain the content of total phenols and flavonoids, and inhibit lignin deposition by inhibiting the activity and gene expression of phenylpropanoid metabolism related enzymes as PAL, C4H, 4CL, CAD, and POD. The results indicate that exogenous MT treatment can effectively inhibit the quality degradation of cold stored water bamboo shoots.

The Flavor Characteristics, Antioxidant Capability, and Storage Year Discrimination Based on Backpropagation Neural Network of Organic Green Tea (Camellia sinensis) during Long-Term Storage

The storage period of tea is a major factor affecting tea quality. However, the effect of storage years on the non-volatile major functional components and quality of green tea remains largely unknown. In this study, a comparative analysis of organic green teas with varying storage years (1-16 years) was conducted by quantifying 47 functional components, using electronic tongue and chromatic aberration technology, alongside an evaluation of antioxidative capacity. The results indicated a significant negative correlation between the storage years and levels of tea polyphenols, total amino acids, soluble sugars, two phenolic acids, four flavonols, three tea pigments, umami amino acids, and sweet amino acids. The multivariate statistical analysis revealed that 10 functional components were identified as effective in distinguishing organic green teas with different storage years. Electronic tongue technology categorized organic green teas with different storage years into three classes. The backpropagation neural network (BPNN) analysis demonstrated that the classification predictive ability of the model based on the electronic tongue was superior to the one based on color difference values and 10 functional components. The combined analysis of antioxidative activity and functional components suggested that organic green teas with shorter storage periods exhibited stronger abilities to suppress superoxide anion radicals and hydroxyl radicals and reduce iron ions due to the higher content of eight components. Long-term-stored organic green teas, with a higher content of substances like L-serine and theabrownins, demonstrated stronger antioxidative capabilities in clearing both lipid-soluble and water-soluble free radicals. Therefore, this study provided a theoretical basis for the quality assessment of green tea and prediction of green tea storage periods.

Fungal Pigments: Carotenoids, Riboflavin, and Polyketides with Diverse Applications

Natural pigments and colorants have seen a substantial increase in use over the last few decades due to their eco-friendly and safe properties. Currently, customer preferences for more natural products are driving the substitution of natural pigments for synthetic colorants. Filamentous fungi, particularly ascomycetous fungi (Monascus, Fusarium, Penicillium, and Aspergillus), have been shown to produce secondary metabolites containing a wide variety of pigments, including β-carotene, melanins, azaphilones, quinones, flavins, ankaflavin, monascin, anthraquinone, and naphthoquinone. These pigments produce a variety of colors and tints, including yellow, orange, red, green, purple, brown, and blue. Additionally, these pigments have a broad spectrum of pharmacological activities, including immunomodulatory, anticancer, antioxidant, antibacterial, and antiproliferative activities. This review provides an in-depth overview of fungi gathered from diverse sources and lists several probable fungi capable of producing a variety of color hues. The second section discusses how to classify coloring compounds according to their chemical structure, characteristics, biosynthetic processes, application, and present state. Once again, we investigate the possibility of employing fungal polyketide pigments as food coloring, as well as the toxicity and carcinogenicity of particular pigments. This review explores how advanced technologies such as metabolic engineering and nanotechnology can be employed to overcome obstacles associated with the manufacture of mycotoxin-free, food-grade fungal pigments.

Changes in sugar, organic acid and free amino acid levels and the expression of genes involved in the primary metabolism of oleocellosis in citrus peels

Oleocellosis is a physiological disorder in citrus fruit and causes extensive economic damage due to the surface blemishes it creates. It was reported that oleocellosis always occurs during preharvest maturation and postharvest storage. In the present study, the oleocellosis incidence of Jincheng orange, Navel orange and Ponkan were found to be different during preharvest maturation, however, no differences were found during postharvest storage. Additionally, it was interesting that the outbreak period of oleocellosis incidence was 0-12 d during postharvest storage. Climate change has been reported as a factor promoting oleocellosis development. However, little information is available regarding how primary metabolites and the expression of genes involved in sugar, organic acid and free amino acid metabolism in citrus change to adjust to new environments. Metabolic profiling obtained by gas chromatography-mass spectrometry (GC‒MS) and amino acid analysis showed that the accumulations of fructose, glucose, sucrose, maltose, mannose, citric acid, α-ketoglutarate, 2-keto-d-gluconic acid, glutamate, valine, glycine and threonine might play major roles in adaptation to changes in oleocellosis peels for three types of citrus fruit. However, decreased contents of malic acid, gluconic acid and proline were observed, possibly due to consumption in energy metabolism or reflecting a unique characteristic in this disorder. Regarding gene expression in primary metabolism pathways obtained by high-throughput mRNA sequencing (RNA-Seq) technology, upregulated genes encoding alpha-glucosidase, beta-glucosidase, beta-fructofuranosidase, alpha-amylase, beta-amylase, malate dehydrogenase, CTP synthase (glutamine hydrolysing), serine-glyoxylate transaminase, serine/glycine hydroxymethyltransferase and proline dehydrogenase were the main changes in this disorder.

Effect of graphene oxide on the uptake, translocation and toxicity of metal mixture to Lepidium sativum L. plants: Mitigation of metal phytotoxicity due to nanosorption

Due to its unique structure and exceptional properties, graphene oxide (GO) is increasingly used in various fields of industry and therefore is inevitably released into the environment, where it interacts with different contaminants. However, the information relating to the ability of GO to affect the toxicity of contaminants is still limited. Therefore, the aim of our study was to synthesize GO, to examine the phytotoxicity of different concentrations of GO and its co-exposure with the metal mixture using garden cress (Lepidium sativum L.) as a test organism and to evaluate the potential of GO to affect toxicity of metals and their uptake by plants. The metal mixture (MIX) containing Ni (II), Zn (II), Cr (III) and Cu (II) was prepared in accordance with the maximum-permissible-concentrations (MPC) accepted for the inland waters in the EU. Additionally, the capacity of GO to adsorb metals was studied in specific conditions of the phytotoxicity test and assessed using adsorption isotherms. Our data indicate that in most cases the tested concentrations of MIX, GO and MIX + GO did not affect seed germination, root growth and biomass of roots and seedlings, however, they were found to alter photosynthesis processes, enhance production of carotenoids and H₂O₂ as well as to activate lipid peroxidation. Additionally, our study revealed that GO affects the accumulation of tested metals in roots and shoots of the MIX-exposed L. sativum. This is due to the capacity of GO to adsorb metals from the growth medium. Therefore, low concentrations of GO can be used for water decontamination.

The molecular mechanism on suppression of climacteric fruit ripening with postharvest wax coating treatment via transcriptome

Wax coating is an important means to maintain fruit quality and extend fruit shelf life, especially for climacteric fruits, such as apples (Malus domestica). Here, we found that wax coating could inhibit ethylene production, chlorophyll degradation, and carotenoid synthesis, but the molecular mechanism remains unclear. The regulatory mechanism of wax coating on apple fruit ripening was determined by subjecting wax-treated apple fruits to transcriptome analysis. RNA-seq revealed that 1,137 and 1,398 genes were upregulated and downregulated, respectively. These differentially expressed genes (DEGs) were shown to be related to plant hormones, such as ethylene, auxin, abscisic acid, and gibberellin, as well as genes involved in chlorophyll degradation and carotenoid biosynthesis. Moreover, we found that some genes related to the wax synthesis process also showed differential expression after the wax coating treatment. Among the DEGs obtained from RNA-seq analysis, 15 were validated by quantitative RT-PCR, confirming the results from RNA-seq analysis. RNA-seq and qRT-PCR of pear (Pyrus ussuriensis) showed similar changes after wax treatment. Our data suggest that wax coating treatment inhibits fruit ripening through ethylene synthesis and signal transduction, chlorophyll metabolism, and carotenoid synthesis pathways and that waxing inhibits endogenous wax production. These results provide new insights into the inhibition of fruit ripening by wax coating.

Transcriptome analyses reveal the potential mechanisms for color changes of a sweet orange peel induced by Candidatus Liberibacter asiaticus

'Shatangju' mandarin (Citrus reticulate Blanco cv. Shatangju) is a Chinese citrus specialty in southern China with a delicious taste and an attractive appearance. Huanglongbing (HLB) caused by Candidatus Liberibacter asiaticus (CLas) threatens the Shatangju industry seriously. Fruits from citrus trees with HLB show 'red nose' peels with a serious reduction in fruit value. Differentially expressed genes (DEGs) have been identified in the leaves of several citrus species with HLB infection. However, similar studies on the fruit peels of citrus trees with HLB infection are very limited. In this study, the pathogen CLas was diagnosed in the 'red nose' fruit peels of Shatangju. The chlorophyll and carotenoid contents in different peels were also analyzed. Besides, we identified DEGs in the comparison between peels from normal red-colored and 'red nose' fruits via RNA-seq. A total of 1922 unigenes were identified as DEGs, of which 434 were up-regulated and 1488 were down-regulated in the 'red nose' fruit peels. DEGs involved in chlorophyll and carotenoids biosynthesis, photosynthesis, and transcription factors could be responsible for fruit color changes after HLB infection. Our findings provide a preliminary understanding of the mechanism underlying the formation of a 'red nose' on fruit peel from HLB-infected trees.

Exogenous Ethylene Promotes Peel Color Transformation by Regulating the Degradation of Chlorophyll and Synthesis of Anthocyanin in Postharvest Mango Fruit

Due to geographical location and climatic factors, postharvest storage and preservation of tropical fruits and vegetables are still facing huge challenges. Ethephon (ETH) is widely used as an ethylene donor to achieve the commercial color and flavor of climacteric fruits. However, the effect of ETH on fruit coloration was affected by many factors, such as fruit species, plant hormones, and storage conditions. In this study, the main mango variety “Guifei” in Hainan, China, was used to study the effects of different concentrations of ETH on fruit ripening and coloration during storage at 25°C. Results showed that postharvest treatment with ETH (300, 500, and 900 mg·L⁻¹) enhanced the activities of ACS and ACO, stimulated the release of endogenous ethylene, and accelerated fruit softening and color transformation. Compared with control, ETH treatment not only accelerated the breakdown of chlorophyll with higher activities of Chlase and MDCase but also induced the synthesis of carotenoid and anthocyanin with higher activities of PAL, CHI, DFR, and UFGT. Moreover, the changes in DFR and UFGT activities coincided with the increase in ETH concentration. Further, correlation analysis showed that the production of endogenous ethylene induced by ETH was significantly negatively correlated with firmness and chlorophyll content, whereas positively correlated with MDA content and anthocyanin content. This study suggests that the positive effect of ETH on “Guifei” mango color transformation is concentration-dependent within a certain concentration range. Anthocyanin is the main pigment for the red formation of “Guifei” mango, and DFR and UFGT may play critical roles in anthocyanin synthesis. ETH promoted the red coloration by promoting the release of endogenous ethylene and enhancing the activities of anthocyanin synthesis enzymes.

Assessment of lemon juice adulteration by targeted screening using LC-UV-MS and untargeted screening using UHPLC-QTOF/MS with machine learning

The aim of this work was to develop an approach combining LC-MS-based metabolomics and machine learning to distinguish between and predict authentic and adulterated lemon juices. A targeted screening of six major flavonoids was first conducted using ultraviolet ion trap MS. To improve the prediction accuracy, an untargeted methodology was carried out using UHPLC-QTOF/MS. Based on the acquired metabolic profiles, both PCA and PLS-DA were conducted. Results exhibited a cluster pattern and a separation potential between authentic and adulterated samples. Five machine learning models were then developed to further analyze the data. The model of support vector machine achieved the highest prediction power, with accuracy up to 96.7 ± 7.5% for the cross-validation set and 100% for the testing set. In addition, 79 characteristic m/z were tentatively identified. This work demonstrated that untargeted screening coupled with machine learning models can be a powerful tool to facilitate detection of lemon juice adulteration.

Fruit transcriptional profiling of the contrasting genotypes for shelf life reveals the key candidate genes and molecular pathways regulating post-harvest biology in cucumber

Cucumber fruits are perishable in nature and become unfit for market within 2-3 days of harvesting. A natural variant, DC-48 with exceptionally high shelf life was developed and used to dissect the genetic architecture and molecular mechanism for extended shelf life through RNA-seq for first time. A total of 1364 DEGs were identified and cell wall degradation, chlorophyll and ethylene metabolism related genes played key role. Polygalacturunase (PG), Expansin (EXP) and xyloglucan were down regulated determining fruit firmness and retention of fresh green colour was mainly attributed to the low expression level of the chlorophyll catalytic enzymes (CCEs). Gene regulatory networks revealed the hub genes and cross-talk associated with wide variety of the biological processes. Large number of SSRs (21524), SNPs (545173) and InDels (126252) identified will be instrumental in cucumber improvement. A web genomic resource, CsExSLDb developed will provide a platform for future investigation on cucumber post-harvest biology.

Color enhancement mechanisms analysis of freeze-dried carrots treated by ultrasound-assisted osmosis (ascorbic acid-CaCl2) dehydration

Color enhancement mechanisms of freeze-dried carrot sample (FDS) treated by ultrasound-assisted osmotic (ascorbic acid-CaCl₂) dehydration (UAA) were comprehensively investigated from physical microstructures and color-related carotenoid compounds. Results of scanning electron microscope and confocal laser scanning microscopy showed that cells in samples treated by UAA were intact, had less porosity and showed stronger carotenoid autofluorescence. As for color-related compounds, UAA not only increased the retention ratios of total carotenoid content (36.38%) and β-carotene (51.73%) of FDS, but also preserved the high raman intensity of CC in-plane expansion (9986 A.U) and induced the formation of coloring-carotenoid-derivatives. Additionally, correlation and PCA-X model analysis showed that fresh carrot had higher extractable color value (78.46), which was positively linearly related to 2-n-pentylfuran (p < 0.01), whereas FDS mainly affected the surface color that was dominated by β-carotene. This work provided the practical analysis and theoretical basis of color enhancement of freeze-dried carrot foods.

Exogenous gibberellin induced regreening through the regulation of chlorophyll and carotenoid metabolism in Valencia oranges

In the present study, we studied the effects of gibberellic acid (GA) on chlorophyll and carotenoid metabolites and related gene expression during the regreening process in Valencia orange fruits (Citrus sinensis Osbeck). During the regreening, fruits treated with GA turned green much faster than those of the control. Compared with untreated fruits, chlorophyll accumulation was induced and the content of carotenoids (β-cryptoxanthin, all-trans-violaxanthin, and 9-cis-violaxanthin) was decreased by the GA treatment. Chlorophyll and carotenoid contents following GA treatment appeared to be highly regulated at the gene transcription level. Correspondingly, the up-regulation of chlorophyll biosynthesis genes (CitGGDR, CitCHL27, CitPORA, and CitCAO) and down-regulation of degradation genes (CitCLH1, CitSGR, CitPPH, CitPAO, and CitRCCR) led to the increase of chlorophyll contents, and the down-regulation of carotenoid biosynthesis genes (CitPSY, CitPDS, CitZDS, CitLCYb2, and CitHYb) led to the decrease of carotenoid contents. These observations indicated that GA acted as a crucial regulator in the regreening process of citrus fruits.

Comparison of Metabolome and Functional Properties of Three Korean Cucumber Cultivars

Cucumber (Cucumis sativus L.) is consumed worldwide and various cultivars have been developed to enhance fruit quality. However, few studies have comprehensively evaluated the quality of various cultivars. We carried out a metabolomics approach to study the three different cucumber cultivars (Chuichung, White Dadagi, and Mini) and their parts (peel and flesh) coupled with antioxidant activities. The amino acids, sugars, flavonoids, carotenoids, and chlorophylls were upregulated in Mini flesh; however, in the case of peel, they were highly expressed in Chuichung. The highest antioxidant activity was observed in the peel of Chuichung and flesh of Mini. Through correlation analysis between metabolites and antioxidant activity, apigenin and quercetin derivatives, chlorophyll a, chlorophyll b, lutein, α-carotene, and β-carotene were found to be significantly positively correlated with antioxidant activity. To understand the metabolism of these compounds, we performed a comprehensive pathway analysis using a metabolomics approach and analysis of associated gene expression. In secondary metabolism, the expression levels of carotenoid-related genes (15-cis-phytoene synthase and ζ-carotene desaturase) and chlorophyll-related genes (protochlorophyllide reductase and glutamyl-tRNA reductase) were consistent with the metabolome analysis data. Collectively, carotenoid and chlorophyll metabolism were upregulated in Chuichung peel and Mini flesh, which had the highest antioxidant activity in each part. These bioactive compounds can be used as biomarkers of commercial cucumber fruit quality. Accordingly, this study offers integrative insights into the quality of different cucumber cultivars and explores valuable metabolites and genes that are helpful in improving quality with functional properties.

Evaluation of quality changes of differently formulated cloudy mixed juices during refrigerated storage after high pressure processing

Cloudy fruit and vegetable mixed juice (MJ) pasteurized by high pressure processing (HPP) showed an increasing market demand. However, browning, sedimentation, and flavor changes of HPP juice during storage have been a great challenge for the beverage industry. The aim of this work was to investigate quality changes of HPP MJs during storage and to explore the potential to create the shelf-stable MJs with fresh-like organoleptic quality through HPP. In the work, commercial MJ1 (orange, mango, and kiwifruit) and MJ2 (carrot and pineapple) were formulated and their quality changes during storage were investigated. The results indicated no visible color changes and sedimentation were observed in MJ1 and MJ2 during refrigerated storage (90 days). However, sucrose decreased as glucose and fructose increased; a large number of aldehydes and alcohols decreased but some terpenoids increased during storage. In general, blending proper fruit and vegetable to produce MJs combing with HPP could maintain high cloud and color stability, but sugars and volatiles clearly changed during storage.

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HPP mixed juice showed high color and cloud stability during chilled storage.

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Aldehydes and alcohols decreased but terpenoids increased during storage.

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Sucrose decreased with glucose and fructose increasing during storage.

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Carrot-pinapple mixed juice showed high quality stability during storgae.

The Application of Phytohormones as Biostimulants in Corn Smut Infected Hungarian Sweet and Fodder Corn Hybrids

The main goal of this research was to investigate the effects of corn smut (Ustilago maydis DC. Corda) infection on the morphological (plant height, and stem diameter), and biochemical parameters of Zea mays L. plants. The biochemical parameters included changes in the relative chlorophyll, malondialdehyde (MDA), and photosynthesis pigments' contents, as well as the activities of antioxidant enzymes-ascorbate peroxidase (APX), guaiacol peroxidase (POD), and superoxide dismutase (SOD). The second aim of this study was to evaluate the impact of phytohormones (auxin, cytokinin, gibberellin, and ethylene) on corn smut-infected plants. The parameters were measured 7 and 11 days after corn smut infection (DACSI). Two hybrids were grown in a greenhouse, one fodder (Armagnac) and one a sweet corn (Desszert 73). The relative and the absolute amount of photosynthetic pigments were significantly lower in the infected plants in both hybrids 11 DACSI. Activities of the antioxidant enzymes and MDA content were higher in both infected hybrids. Auxin, cytokinin, and gibberellin application diminished the negative effects of the corn smut infection (CSI) in the sweet corn hybrid. Phytohormones i.e., auxin, gibberellin, and cytokinin can be a new method in protection against corn smut.

Cold acclimation can specifically inhibit chlorophyll biosynthesis in young leaves of Pakchoi

BACKGROUND

Leaf color is an important trait in breeding of leafy vegetables. Y-05, a pakchoi (Brassica rapa ssp. chinensis) cultivar, displays yellow inner (YIN) and green outer leaves (GOU) after cold acclimation. However, the mechanism of this special phenotype remains elusive.

RESULTS

We assumed that the yellow leaf phenotype of Y-05 maybe caused by low chlorophyll content. Pigments measurements and transmission electron microscopy (TEM) analysis showed that the yellow phenotype is closely related with decreased chlorophyll content and undeveloped thylakoids in chloroplast. Transcriptomes and metabolomes sequencing were next performed on YIN and GOU. The transcriptomes data showed that 4887 differentially expressed genes (DEGs) between the YIN and GOU leaves were mostly enriched in the chloroplast- and chlorophyll-related categories, indicating that the chlorophyll biosynthesis is mainly affected during cold acclimation. Together with metabolomes data, the inhibition of chlorophyll biosynthesis is contributed by blocked 5-aminolevulinic acid (ALA) synthesis in yellow inner leaves, which is further verified by complementary and inhibitory experiments of ALA. Furthermore, we found that the blocked ALA is closely associated with increased BrFLU expression, which is indirectly altered by cold acclimation. In BrFLU-silenced pakchoi Y-05, cold-acclimated leaves still showed green phenotype and higher chlorophyll content compared with control, meaning silencing of BrFLU can rescue the leaf yellowing induced by cold acclimation.

CONCLUSIONS

Our findings suggested that cold acclimation can indirectly promote the expression of BrFLU in inner leaves of Y-05 to block ALA synthesis, resulting in decreased chlorophyll content and leaf yellowing. This study revealed the underlying mechanisms of leaves color change in cold-acclimated Y-05.

Characterization of BoaCRTISO Reveals Its Role in Carotenoid Biosynthesis in Chinese Kale

Carotenoids are organic pigments that play an important role in both plant coloration and human health; they are a critical subject in molecular breeding due to growing demand for natural molecules in both food and medicine. In this study, we focus upon characterizing BoaCRTISO, the carotenoid isomerase gene before the branch of the carotenoid biosynthetic pathway, which is expressed in all organs and developmental stages of Chinese kale, and BoaCRTISO, which is located in the chloroplast. The expression of BoaCRTISO is induced by strong light, red and blue combined light, and gibberellic acid treatment, but it is suppressed by darkness and abscisic acid treatment. We obtained BoaCRTISO-silenced plants via virus-induced gene silencing technology, and the silence efficiencies ranged from 52 to 77%. The expressions of most carotenoid and chlorophyll biosynthetic genes in BoaCRTISO-silenced plants were downregulated, and the contents of carotenoids and chlorophyll were reduced. Meanwhile, BoaCRTISO-silenced plants exhibited phenotypes of yellowing leaves and inhibited growth. This functional characterization of BoaCRTISO provides insight for the biosynthesis and regulation of carotenoid in Chinese kale.

Metabolome and transcriptome analyses reveal chlorophyll and anthocyanin metabolism pathway associated with cucumber fruit skin color

BACKGROUND

Fruit skin color play important role in commercial value of cucumber, which is mainly determined by the content and composition of chlorophyll and anthocyanins. Therefore, understanding the related genes and metabolomics involved in composition of fruit skin color is essential for cucumber quality and commodity value.

RESULTS

The results showed that chlorophyll a, chlorophyll b and carotenoid content in fruit skin were higher in Lv (dark green skin) than Bai (light green skin) on fruit skin. Cytological observation showed more chloroplast existed in fruit skin cells of Lv. A total of 162 significantly different metabolites were found between the fruit skin of the two genotypes by metabolome analysis, including 40 flavones, 9 flavanones, 8 flavonols, 6 anthocyanins, and other compounds. Crucial anthocyanins and flavonols for fruit skin color, were detected significantly decreased in fruit skin of Bai compared with Lv. By RNA-seq assay, 4516 differentially expressed genes (DEGs) were identified between two cultivars. Further analyses suggested that low expression level of chlorophyll biosynthetic genes, such as chlM, por and NOL caused less chlorophylls or chloroplast in fruit skin of Bai. Meanwhile, a predicted regulatory network of anthocyanin biosynthesis was established to illustrate involving many DEGs, especially 4CL, CHS and UFGT.

CONCLUSIONS

This study uncovered significant differences between two cucumber genotypes with different fruit color using metabolome and RNA-seq analysis. We lay a foundation to understand molecular regulation mechanism on formation of cucumber skin color, by exploring valuable genes, which is helpful for cucumber breeding and improvement on fruit skin color.

ROS Homeostasis in Abiotic Stress Tolerance in Plants

Climate change-induced abiotic stress results in crop yield and production losses. These stresses result in changes at the physiological and molecular level that affect the development and growth of the plant. Reactive oxygen species (ROS) is formed at high levels due to abiotic stress within different organelles, leading to cellular damage. Plants have evolved mechanisms to control the production and scavenging of ROS through enzymatic and non-enzymatic antioxidative processes. However, ROS has a dual function in abiotic stresses where, at high levels, they are toxic to cells while the same molecule can function as a signal transducer that activates a local and systemic plant defense response against stress. The effects, perception, signaling, and activation of ROS and their antioxidative responses are elaborated in this review. This review aims to provide a purview of processes involved in ROS homeostasis in plants and to identify genes that are triggered in response to abiotic-induced oxidative stress. This review articulates the importance of these genes and pathways in understanding the mechanism of resistance in plants and the importance of this information in breeding and genetically developing crops for resistance against abiotic stress in plants.

Addition of Orange Peel in Orange Jam: Evaluation of Sensory, Physicochemical, and Nutritional Characteristics

Orange is highly nutritious and a source of phytochemical compounds. However, its by-products are usually discarded. In this study, we evaluated the effect of orange peel (OP) addition in orange jam on sensory, physicochemical, and nutritional characteristics. Four jam formulations were elaborated with different OP levels: OP0 (standard), OP4, OP8, and OP12 (Orange Peel 0, 4, 8 and 12%, respectively). All samples were evaluated for sensory acceptability, and physicochemical and nutritional composition. The addition of 12% orange peel in jam reduced (p < 0.05) the acceptability for all evaluated attributes, as well as overall acceptance and purchase intention. However, OP utilization increased (p < 0.05) the levels of water activity, soluble solids, titratable acidity, and sugars. Soluble solids/titratable acidity ratio, luminosity (L*), and yellow content (b*) decreased in all added OP jams, while red content (a*) increased. No change in the pH and moisture values of the product were observed after OP addition. Ash, protein, lipid, dietary fiber, ascorbic acid, carotenoids, phenolic compounds, and antioxidant capacity values increased after OP addition, while carbohydrate and energy content decreased. A texture test showed that adhesiveness decreased, while gumminess, chewiness, and elasticity increased after OP addition. We concluded that the addition of up to 8% orange peel in jam maintains sensory acceptability similar to that of the standard product. OP addition is a viable alternative to improve some of the product's physicochemical and nutritional characteristics.

Response of photosynthesis to different concentrations of heavy metals in Davidia involucrata

Lead (Pb) and cadmium (Cd) are highly toxic and are widespread in agricultural soils, representing risks to plant and human health. In this study, Davidia involucrata was cultivated in soil with different concentrations of Pb and Cd and sampled after 90 days. We used ANOVA to analyse the photosynthesis of D. involucrata and the ability of Pb and Cd to enrich and migrate in roots, stems and leaves. Various results are described here. 1) Under individual and combined Pb and Cd stress, the accumulation factors in the roots were greater than 1, which was significantly greater than those in the stems and leaves (P < 0.05), and the translocation factors both were less than 1. The Pb and Cd enrichment ability of D. involucrata roots was significantly higher than that of stems and leaves, and the migration ability of the two heavy metals in D. involucrata was weak. 2) The Mg-dechelatase activities of chlorophyll degradation products increased under stress due to high concentrations of Pb and Cd. However, chlorophyllase activity was higher at relatively low concentrations of the two heavy metals (P < 0.05). δ-Aminolevulinic acid and porphobilinogen of chlorophyll synthesis products are easily converted to uroporphyrinogen III under low concentrations of Cd, which promotes the synthesis of chlorophyll. 3) The effect of Cd stress alone on the chlorophyll concentration was not significant. Under combined stress, concentrations of Pb and Cd in the range of 400~800 mg·kg-1 and 5~20 mg·kg-1 significantly promoted an increase in photosynthetic pigments (P < 0.05). 4) Inhibition of the net photosynthetic rate increased with increasing Pb and Cd concentrations under both individual and combined stress. In addition, the root of D. involucrata had a strong absorption and fixation effect on heavy metals, thereby reducing metal toxicity and improving the tolerance of D. involucrata to heavy metals.