Integrated transcriptomic and metabolomic analyses reveal key genes controlling flavonoid biosynthesis in Citrus grandis 'Tomentosa' fruits.

As a well-recognized traditional Chinese medicine (TCM), immature fruits of Citrus grandis 'Tomentosa' (CGT) serve to cure chronic cough in humans. Specialized metabolites including flavonoids may have contribute to this curing effect. Knowledge about the molecular mechanisms underlying flavonoid biosynthesis in 'Tomentosa' fruits will, therefore, support the breeding of varieties with improved medicinal properties. Hence, we profiled the transcriptomes and metabolites of the fruits of two contrasting C. grandis varieties, namely 'Zheng-Mao' ('ZM') used in TCM production, and a locally cultivated pomelo, namely 'Guang-Qing' ('GQ'), at four developmental stages. A total of 39 flavonoids, including 14 flavanone/flavone, 5 isoflavonoids, 12 flavonols, and 6 anthocyanins, were identified, and 16 of which were quantitatively determined in the fruits of the two varieties. We found that 'ZM' fruits contain more flavonoids than 'GQ'. Specifically, rhoifolin levels were significantly higher in 'ZM' than in 'GQ'. We annotated 31,510 genes, including 1,387 previously unknown ones, via transcriptome sequencing of 'ZM' and 'GQ.' A total of 646 genes were found to be differentially expressed between 'ZM' and 'GQ' throughout at all four fruit developmental stages, indicating that they are robust expression markers for future breeding programs. Weighted gene co-expression network analysis identified 18 modules. Combined transcriptional and metabolic analysis revealed 25 genes related to flavonoid biosynthesis and 16 transcriptional regulators (MYBs, bHLHs, WD40) that may be involved in the flavonoids biosynthesis in C. grandis 'Tomentosa' fruits.

Arsenic inhibits citric acid accumulation via downregulating vacuolar proton pump gene expression in citrus fruits.

Citric acid content is a critical quality determinant in citrus (Citrus spp.) fruits. Although arsenic (As) can effectively reduce citric acid content to improve citrus fruit quality, it can have adverse environmental effects. The discovery of nontoxic substitutes is hampered by the incomplete elucidation of the underlying mechanisms of As action in citrus fruits. Metabolic, transcriptomic, and physiological analyses were employed to investigate As action on citric acid accumulation to discover the mechanisms of As action in citrus. The enzyme activity related to citrate biosynthesis was not inhibited and the content of the involved metabolites was not reduced in As-treated fruits. However, the proton pump genes CitPH5 and CitPH1 control the vacuolar citric acid accumulation and transcription factor genes CitTT8 and CitMYB5, which regulate CitPH5 and CitPH1, were downregulated. The oxidative stress-response genes were upregulated in As-treated fruits. The reactive oxygen species (ROS) treatment also downregulated CitTT8 and CitMYB5 in juice cells. The mitochondrial ROS production rate increased in As-treated fruits. AsIII was more potent in stimulating isolated mitochondria to overproduce ROS compared to AsV. Our results indicate that the As inhibition of citric acid accumulation may be primarily due to the transcriptional downregulation of CitPH5, CitPH1, CitTT8, and CitMYB5. As-induced oxidative stress signaling may operate upstream to downregulate these acid regulator genes. Mitochondrial thiol proteins may be the principal targets of As action in citrus fruits.

Comparative investigation of bioflavonoid electrocatalysis in 1D, 2D, and 3D carbon nanomaterials for simultaneous detection of naringin and hesperidin in fruits.

Electrocatalysis of bioflavonoids in carbon nanomaterials plays an important role in electrochemical sensors for the detection of their content in fruits. In this study, three types of carbon nanomaterials with 1D, 2D, and 3D structures, namely carbon nanotubes (CNTs), graphene oxide (GO), and Ketjen black (KB), were modified onto glassy carbon electrodes for the electrocatalysis of hesperidin and naringin, which are two important bioflavonoids in fruits. As a result, the CNT-modified electrodes showed the highest electrocatalytic activity for both hesperidin and naringin compared to GO and KB. The morphology and surface chemistry of the carbon nanomaterials were characterized. The structural defects and carbon status of carbon nanomaterials are proposed to be the most important factors affecting the electrocatalysis of hesperidin and naringin. Finally, a CNT-based electrochemical sensor was fabricated to simultaneously detect hesperidin and naringin. Real sample tests on the fruit extract of Citrus grandis "Tomentosa" show that the proposed electrochemical sensors with high recovery thus could be employed in practical applications.

Chemical elucidation and rheological properties of a pectic polysaccharide extracted from Citrus medica L. fruit residues by gradient ethanol precipitation.

Citron (Citrus. medica L.) fruits are commonly utilized in the production of essential oil, therefore, the fruits residues turn out to be industrial byproducts. In the present study, a crude polysaccharide was extracted from citron fruit residues by hot water extraction and precipitation of ethanol (95%), after deproteinization, a major polysaccharide component (CMLP-2) was obtained by gradient ethanol precipitation (20%-80%). The physicochemical properties of CMLP-2 such as surface morphology, functional groups, and thermostability were examined by FT-IR spectroscopy, SEM, and thermogravimetric analysis. Moreover, the chemical structure of CMLP-2 was elucidated that CMLP-2 is an acidic pectic polysaccharide consisting of arabinose (Ara), galacturonic acid (GalA), and rhamnose (Rha) in a molar ratio of 4:2:1 with a molecular weight of 202.18 kDa. CMLP-2 is a novel pectic polysaccharide rich in rhamnogalacturonan I (RG-I). Moreover, rheological tests revealed that CMLP-2 solution is pseudoplastic and temperature resistant. The result could be a good basis for the utilization of Citrus medica L. fruits residues as plant-derived food additive.

A comparative UPLC-Q-Orbitrap-MS untargeted metabolomics investigation of different parts of Clausena lansium (Lour.) Skeels.

In this study, the non-targeted large-scale plant metabolomics (UPLC-Q-Orbitrap-MS) was performed for the comparison of chemical profiling of the leaves, barks, flowers, peels, pulps, and seeds of Clausena lansium (Lour.) Skeels (called "wampee"). A total of 364 metabolites were identified, and 62 potential biomarkers were selected by the multivariate statistical analysis. Hierarchical cluster analysis suggested that the selected biomarkers were significant differential metabolites among various parts of wampee. Metabolic pathway analysis showed a significant enrichment of the "Flavone and flavonol synthesis" and "Isoquinoline alkaloid biosynthesis" pathway. This study provides important information for the isolation and identification of functional components from different tissues of wampee and the metabolic biosynthesis pathway elucidation in detail.

Contribution of anthocyanin pathways to fruit flesh coloration in pitayas.

BACKGROUND: Color formation in Hylocereus spp. (pitayas) has been ascribed to the accumulation of betalains. However, several studies have reported the presence of anthocyanins in pitaya fruit and their potential role in color formation has not yet been explored. In this study, we profiled metabolome and transcriptome in fruit of three cultivars with contrasting flesh colors (red, pink and white) to investigate their nutritional quality and the mechanism of color formation involving anthocyanins. RESULTS: Results revealed that pitaya fruit is enriched in amino acid, lipid, carbohydrate, polyphenols, vitamin and other bioactive components with significant variation among the three cultivars. Anthocyanins were detected in the fruit flesh and accumulation levels of Cyanidin 3-glucoside, Cyanidin 3-rutinoside, Delphinidin 3-O-(6-O-malonyl)-beta-glucoside-3-O-beta-glucoside and Delphinidin 3-O-beta-D-glucoside 5-O-(6-coumaroyl-beta-D-glucoside) positively correlated with the reddish coloration. Transcriptome data showed that the white cultivar tends to repress the anthocyanin biosynthetic pathway and divert substrates to other competing pathways. This perfectly contrasted with observations in the red cultivar. The pink cultivar however seems to keep a balance between the anthocyanin biosynthetic pathway and the competing pathways. We identified several active transcription factors of the MYB and bHLH families which can be further investigated as potential regulators of the anthocyanin biosynthetic genes. CONCLUSIONS: Collectively, our results suggest that anthocyanins partly contribute to color formation in pitaya fruit. Future studies aiming at manipulating the biosynthetic pathways of anthocyanins and betalains will better clarify the exact contribution of each pathway in color formation in pitayas. This will facilitate efforts to improve pitaya fruit quality and appeal.

Genome-Wide Identification and Characterization of the NAC Transcription Factor Family in Musa Acuminata and Expression Analysis during Fruit Ripening.

Banana (Musa acuminata, AAA group) is a representative climacteric fruit with essential nutrients and pleasant flavors. Control of its ripening determines both the fruit quality and the shelf life. NAC (NAM, ATAF, CUC2) proteins, as one of the largest superfamilies of transcription factors, play crucial roles in various functions, especially developmental processes. Thus, it is important to conduct a comprehensive identification and characterization of the NAC transcription factor family at the genomic level in M. acuminata. In this article, a total of 181 banana NAC genes were identified. Phylogenetic analysis indicated that NAC genes in M. acuminata, Arabidopsis, and rice were clustered into 18 groups (S1-S18), and MCScanX analysis disclosed that the evolution of MaNAC genes was promoted by segmental duplication events. Expression patterns of NAC genes during banana fruit ripening induced by ethylene were investigated using RNA-Seq data, and 10 MaNAC genes were identified as related to fruit ripening. A subcellular localization assay of selected MaNACs revealed that they were all localized to the nucleus. These results lay a good foundation for the investigation of NAC genes in banana toward the biological functions and evolution.

Activation of RAW264.7 macrophages by an acidic polysaccharide derived from Citrus grandis 'Tomentosa'.

Citrus grandis 'Tomentosa' which is a special Citrus cultivar, has been employed as cough suppressant and expectorant in traditional Chinese medicine for thousands of years. The aim of this study is to investigate the immunomodulatory role of an acidic polysaccharide (designated as CGTP-AP) purified from C. grandis 'Tomentosa'. CGTP-AP showed effective immune activation in RAW264.7 macrophages at the concentration of 1-100 µg/mL. CGTP-AP could promote the release of NO in dose- and time-dependent manners. Enzyme-Linked Immunosorbent Assay (ELISA) and RT-PCR analysis demonstrated that CGTP-AP could stimulate the secretion of TNF-α and IL-6 in a dosage-dependent way. Western blot analysis and RT-PCR analysis indicated that CGTP-AP treatment could induce the iNOS and COX-2 expression in RAW264.7 macrophages. By conducting the inhibitors experiments, the activation of NF-κB and MAPK signaling pathways by CGTP-AP treatment was confirmed. Therefore, the present results declared that CGTP-AP could be a promising candidate as a potent immunomodulator for the application in future pharmaceutical development.

Structural elucidation of an acidic polysaccharide from Citrus grandis 'Tomentosa' and its anti-proliferative effects on LOVO and SW620 cells.

Citrus grandis 'Tomentosa' (CGT) which is a region-famous medicinal and edible plant contains plentiful bioactive polysaccharides, however, its chemical structures and specific bioactivities still need to be further explored. In the present study, an acidic polysaccharide (CGTP-AP) was extracted and purified from the pulps of CGT. The structure elucidation and anti-cancer activity of CGTP-AP were investigated. Structure characterization indicated that CGTP-AP was a homogeneous heteropolysaccharide composed of arabinose, galactose and galacturonic acid in a molar ratio of 2.45:1:2.77, with an average molecular weight of 2721.68 kDa. Partial acid hydrolysis, methylation and NMR spectrometry revealed that the backbone of CGTP-AP mainly composed of (1 → 4)-α-D-galacturonan, while the branch principally consisted of (1 → 5)-α-L-Araf. In addition, CGTP-AP exhibited effective anti-proliferation against colon cancer cells LOVO and SW620 cells in dose- and time-dependent manners, with IC50 values of 5.55, 4.35 and 3.52 mg mL-1 after 24, 48 and 72 h, and 5.33, 3.63 and 2.97 mg mL-1 after 24, 48 and 72 h, respectively. This study indicated that CGTP-AP might be utilized as a promising food supplement for the patients of colon disorders.

Plant tannin immobilized Fe3O4@SiO2 microspheres: A novel and green magnetic bio-sorbent with superior adsorption capacities for gold and palladium.

In this paper, a new core-shell nanostructured magnetic bio-based composite was prepared by immobilizing persimmon tannin (PT) onto Fe3O4@SiO2 microspheres, and the as designed Fe3O4@SiO2@PT was utilized for adsorptive recovery of Au(III) and Pd(II). The preparation, morphology, composition and magnetic property of Fe3O4@SiO2@PT were characterized. Adsorption parameters of Fe3O4@SiO2@PT towards Au(III) and Pd(II) including initial pH, reaction time, initial concentration of metal ions, effect of acidity and interference of coexisting metal ions were investigated. It is sufficiently confirmed that silica was coated on Fe3O4 and persimmon tannin was immobilized on aminated Fe3O4@SiO2. The thickness of silica and loaded persimmon tannin are around 18 nm and 14 nm, respectively. With only 1.00 wt% of persimmon tannin, however, the maximum adsorption capacities of Fe3O4@SiO2@PT for Au(III) and Pd(II) were as high as 917.43 and 196.46 mg·g-1, respectively. In addition, after adsorption of Au(III) and Pd(II), the magnetization saturation values (Ms) of Fe3O4@SiO2@PT were high enough to guarantee efficient magnetic seperation. Metallic gold could be facilely recovered from wastewaters containing Au(III).

Selective adsorption and recovery of Au(III) from three kinds of acidic systems by persimmon residual based bio-sorbent: a method for gold recycling from e-wastes.

A low cost bio-sorbent, named "PPF resin", was prepared by crosslinking the persimmon residual with formaldehyde. The adsorption behavior of PPF resin towards Au(III) from varied HCl and HNO3 concentration solutions was studied. PPF resin could adsorb almost complete Au(III) from high acidic systems. The influence of dilution ratio, solid-liquid ratio and time towards Au(III) from aqua regia leached PCBs liquor was censored in detail by batch and continuous adsorption methods. The PPF resin before and after adsorption was characterized by FT-IR, XRD and XPS spectra which provided evidences for the reduction of Au(III) to Au(0) with a proposed mechanism of Au(III) adsorption-reduction process. After saturated column adsorption of 0.1g PPF resin, 0.0506 g gold (purity: 99.9%) was obtained by the method of incineration. The present results provide a new approach for gold recovery from the secondary resources.