Expression Of Biosynthesis-related Genes Research Articles

Exogenous abscisic acid reduces saikosaponin accumulation by inhibiting saikosaponin synthesis pathway gene expression under drought stress in Bupleurum chinense DC.

Abscisic acid (ABA) plays an important role in stress resistance and secondary metabolism of plants under drought stress. Bupleurum chinense DC. is a medicinal plant cultivated in arid areas in China. In this study, the effects of progressive drought stress (22 days) and exogenous ABA (5 mg L–1) treatment on plant physiological characteristics and saikosaponin secondary metabolism were investigated in 2-year-old B. chinense. The samples were collected on 6, 10, 14, 18 and 22 days after drought stress (DADS). In drought stressed B. chinense plants treated with ABA, root weight loss and malondialdehyde accumulation was reduced, while drought resistance increased, as indicated by the accumulation of soluble protein and soluble sugar content, and by the increased activities of superoxide dismutase and peroxidase. At the early stage of drought stress (first 6 days), saikosaponin increased more sharply in plants exposed to drought stress and its accumulation indicated increased sensitivity to this condition. At this time, saikosaponin content reached 31.83 mg g−1, which was 33.6 % higher than that in control plants. Using principal component analysis and fuzzy membership function calculation, comprehensive evaluation values of gene expression in the drought (D) and D + ABA treated groups at different drought exposure time were evaluated. Exogenous ABA inhibited the expression of saikosaponin biosynthesis-related genes from 6 to 14 DADS of drought stress. However, gene expression was up-regulated at later stages of drought stress (the 22 DADS), while genes involved in saikosaponin content were down-regulated in the D group compared with those in the D + ABA group. Indeed, saikosaponin content in both of these groups was significantly higher than that in the control group. Correlation analysis suggested that the expression of 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGR) gene was positively correlated with total saikosaponin (SSs) (p < 0.01), and saikosaponin a (SS-a) and saikosaponin d (SS-d) (p < 0.05) content, while that of farnesyl pyrophosphate synthase (FPS) gene was positively correlated with SSs (p < 0.05), and SS-a and SS-d (p < 0.01) content in the D group. These results indicated that HMGR and FPS play a key role in saikosaponin biosynthesis during drought stress. Moreover, the negative correlations between multiple genes and saikosaponin after ABA treatment [particularly that of cytochrome P450−7 with SS-d (p < 0.01) and glycosyl transferase-8 with SS-d (p < 0.05)], indicated that exogenous ABA reduced saikosaponin accumulation by inhibiting the expression of saikosaponin biosynthesis-related genes in B. chinense exposed to drought stress. This study provides new insight into the effect of ABA on secondary metabolism and it will be of great importance to cultivators and researchers aiming to understand how ABA application affects medicinal plant cultivation.

Inhibitory Effects of Eurotium cristatum on Growth and Aflatoxin B1 Biosynthesis in Aspergillus flavus.

Probiotic strain Eurotium cristatum was isolated from Chinese Fuzhuan brick-tea and tested for its in vitro activity against aflatoxigenic Aspergillus flavus. Results indicated that E. cristatum can inhibit the radial growth of A. flavus. Furthermore, this inhibition might be caused by E. cristatum secondary metabolites. The ability of culture filtrate of strain E. cristatum against growth and aflatoxin B1 production by toxigenic A. flavus was evaluated in vitro. Meanwhile, the influence of filtrate on spore morphology of A. flavus was analyzed by scanning electron microscopy (SEM). Results demonstrated that both radial growth of A. flavus and aflatoxin B1 production were significantly weakened following increases in the E. cristatum culture filtrate concentration. In addition, SEM showed that the culture filtrate seriously damaged hyphae morphology. Gas chromatography mass spectrometry (GC/MS) analysis of the E. cristatum culture supernatant revealed the presence of multiple antifungal compounds. Real-time quantitative polymerase chain reaction (RT-qPCR) analysis showed that the expression of aflatoxin biosynthesis-related genes (aflD, aflQ, and aflS) were down-regulated. Importantly, this latter occurrence resulted in a reduction of the AflS/AflR ratio. Interestingly, cell-free supernatants of E. cristatum facilitated the effective degradation of aflatoxin B1. In addition, two degradation products of aflatoxin B1 lacking the toxic and carcinogenic lactone ring were identified. A toxicity study on the HepG2 cells showed that the degradation compounds were less toxic when compared with AFB1.

SNP in DFR1 Coding Sequence Is Tightly Associated with Anthocyanin Accumulation in Cabbage (B. oleracea var. capitata f. alba) at Low Temperature

Keeping green leaf color at the time of harvest is one of the important traits for breeding of Brassica oleracea var. capitata f. alba, and this trait is related to low anthocyanin contents. To understand the differential accumulation of anthocyanins in cabbage, we selected high anthocyanin accumulators (HAAs) and low anthocyanin accumulator (LAAs) of cabbages and examined the anthocyanin content and the expression of anthocyanin biosynthesis-related genes. Among many genes investigated, BoDFR1 was found to be closely related to anthocyanin accumulation, even under low temperature (LT) conditions. BoDFR1 sequence analyses between HAAs and LAAs revealed that there is a single nucleotide polymorphism (SNP) (1118T/A) in the coding sequence, which substitutes one amino acid from Leu261 to His261; we named BoDFR1 with His261 substitution as BoDFR1v. This amino acid substitution did not affect dihydroflavonol 4-reductase (DFR) activity and substrate specificity, but the polymorphism showed tight association to the BoDFR1 expression, i.e., high level expression of BoDFR1 and low level expression of BoDFR1v under LT conditions. The high levels of BoDFR1 expression were due to the high levels of BoMYB114 and BobHLH expressions combined with low level expression of BoMYBL2, a repressor MYB. On the other hand, low levels of BoDFR1v expression seemed to be related to very low level expressions of BoMYB114 and BobHLH combined with a high level expression of BoMYBL2. It seems that different expression levels of these regulatory genes for MBW (MYB-bHLH-WD40) complex between HAAs and LAAs regulate BoDFR expression and anthocyanin accumulation. Using a single nucleotide polymorphism (SNP) between BoDFR1 and BoDFR1v, molecular markers for PCR and high resolution melt analyses were developed and validated to distinguish between HAAs and LAAs. Combined use of the BoDFR1 SNP marker with other stress markers, such as a cold tolerant marker, will greatly improve cabbage breeding.

Drought stress modify cuticle of tender tea leaf and mature leaf for transpiration barrier enhancement through common and distinct modes

Cuticle is the major transpiration barrier that restricts non-stomatal water loss and is closely associated with plant drought tolerance. Although multiple efforts have been made, it remains controversial what factors shape up the cuticular transpiration barrier. Previously, we found that the cuticle from the tender tea leaf was mainly constituted by very-long-chain-fatty-acids and their derivatives while alicyclic compounds dominate the mature tea leaf cuticle. The presence of two contrasting cuticle within same branch offered a unique system to investigate this question. In this study, tea seedlings were subjected to water deprivation treatment, cuticle structures and wax compositions from the tender leaf and the mature leaf were extensively measured and compared. We found that cuticle wax coverage, thickness, and osmiophilicity were commonly increased from both leaves. New waxes species were specifically induced by drought; the composition of existing waxes was remodeled; the chain length distributions of alkanes, esters, glycols, and terpenoids were altered in complex manners. Drought treatment significantly reduced leaf water loss rates. Wax biosynthesis-related gene expression analysis revealed dynamic expression patterns dependent on leaf maturity and the severity of drought. These data suggested that drought stress-induced structural and compositional cuticular modifications improve cuticle water barrier property. In addition, we demonstrated that cuticle from the tender leaf and the mature leaf were modified through both common and distinct modes.

Overexpression of OsMYB305 in Rice Enhances the Nitrogen Uptake Under Low-Nitrogen Condition.

Excessive nitrogen fertilizer application causes severe environmental degradation and drives up agricultural production costs. Thus, improving crop nitrogen use efficiency (NUE) is essential for the development of sustainable agriculture. Here, we characterized the roles of the MYB transcription factor OsMYB305 in nitrogen uptake and assimilation in rice. OsMYB305 encoded a transcriptional activator and its expression was induced by N deficiency in rice root. Under low-N condition, OsMYB305 overexpression significantly increased the tiller number, shoot dry weight and total N concentration. In the roots of OsMYB305-OE rice lines, the expression of OsNRT2.1, OsNRT2.2, OsNAR2.1, and OsNiR2 was up-regulated and 15NO3– influx was significantly increased. In contrast, the expression of lignocellulose biosynthesis-related genes was repressed so that cellulose content decreased, and soluble sugar concentration increased. Certain intermediates in the glycolytic pathway and the tricarboxylic acid cycle were significantly altered and NADH-GOGAT, Pyr-K, and G6PDH were markedly elevated in the roots of OsMYB305-OE rice lines grown under low-N condition. Our results revealed that OsMYB305 overexpression suppressed cellulose biosynthesis under low-nitrogen condition, thereby freeing up carbohydrate for nitrate uptake and assimilation and enhancing rice growth. OsMYB305 is a potential molecular target for increasing NUE in rice.

Melatonin mitigates cadmium and aluminium toxicity through modulation of antioxidant potential in Brassica napus L

Melatonin has emerged as an essential molecule in plants, due to its role in defence against metal toxicity. Aluminium (Al) and cadmium (Cd) toxicity inhibit rapeseed seedling growth. In this study, we applied different doses of melatonin (50 and 100µm) to alleviate Al (25µm) and Cd (25µm) stress in rapeseed seedlings. Results show that Al and Cd caused toxicity in rapeseed seedling, as evidenced by a decrease in height, biomass and antioxidant enzyme activity. Melatonin increased the expression of melatonin biosynthesis-related Brassica napus genes for caffeic acid O-methyl transferase (BnCOMT) under Al and Cd stress. The genes BnCOMT-1, BnCOMT-5 and BnCOMT-8 showed up-regulated expression, while BnCOMT-4 and BnCOMT-6 were down-regulated during incubation in water. Melatonin application increased the germination rate, shoot length, root length, fresh and dry weight of seedlings. Melatonin supplementation under Al and Cd stress increased superoxide dismutase, catalase, peroxidase, ascorbate peroxidase, proline, chlorophyll and anthocyanin content, as well as photosynthesis rate. Both Cd and Al treatments significantly increased hydrogen peroxide and malondialdehyde levels in rapeseed seedlings, which were strictly counterbalanced by melatonin. Analysis of Cd and Al in different subcellular compartments showed that melatonin enhanced cell wall and soluble fractions, but reduced the vacuolar and organelle fractions in Al- and Cd-treated seedlings. These results suggest that melatonin-induced improvements in antioxidant potential, biomass, photosynthesis rate and successive Cd and Al sequestration play a pivotal role in plant tolerance to Al and Cd stress. This mechanism may have potential implications in safe food production.

Analysis of flavonoids and anthocyanin biosynthesis-related genes expression reveals the mechanism of petal color fading of Malus hupehensis (Rosaceae)

Malus hupehensis (Pamp.) Rehder is an indigenous wild crabapple tree from China that has received increased attention, due to its significant ornamental and economical values. The flowers change from red to white during development, a phenomenon that is prevalent within Malus genus. However, there are no reports on the phytochemical aspects of M. hupehensis flower. Here, we investigated the mechanism of color fading through biochemical and molecular analysis of M. hupehensis petals during development. Sixteen flavonoids were detected, and cyanidin-3-galactoside was the major anthocyanin in petals. The levels of most compounds initially increased and then decreased during flower development. The changing profile of total anthocyanins was consistent with the changes in floral color. Analysis of anthocyanin biosynthesis-related genes showed that the expression levels of PAL, CHS, CHI, DFR, FLS, ANS, UFGT, MYB10 and MYB12 were significantly higher at early stages than at later stages, similarly to the change in cyanidin-3-galactoside contents. MYB10 and MYB12 significantly positively correlated with CHS, CHI and DFR. There was a particularly strong positive correlation between MYB10 and ANS, and MYB12 was strongly positively correlated with LAR. Thus, MYB10 appeared to regulate mainly anthocyanin biosynthesis, and MYB12 could influence the expression of multiple structural genes in both the anthocyanin and flavanol pathways. By contrast, MYB6, bHLH33 and WD40 were significantly and positively correlated with one another but negatively correlated with the levels of many compounds and most structural genes, indicating that these three transcription factors could regulate together anthocyanin biosynthesis. Our results revealed the information about the temporal and spatial regulation of anthocyanin biosynthesis in M. hupehensis and provide the diverse flower color intensities and patterning in Chinese crabapple.

Integrating physiological and metabolites analysis to identify ethylene involvement in petal senescence in Tulipa gesneriana

Flower senescence is classified into ethylene-dependent and ethylene-independent manners and determines the flower longevity which is valuable for ornamental plants. However, the manner of petal senescence in tulip is still less defined. In this study, we characterized the physiological indexes in the process of petal senescence, as well as metabolic and ethylene responses in tulip cultivar ‘American Dream’, and further identified the role of ethylene biosynthesis genes TgACS by transgenic and transient assays. Primary metabolites profiling revealed that sugars, amino acids and organic acids preferentially accumulated in senescent petals. Additionally, senescence-associated genes were identified and significantly up-regulated, coupled with increased ROS contents, rapid water loss and accelerated cell membrane breakdown. Moreover, ethylene production was stimulated as evidenced by increasing in ACS activity and ethylene biosynthesis-related genes expression. Exogenous treatment of cutting flowers with 1-MCP or ethephon resulted in delayed or enhanced petal senescence, respectively. Transient down-regulation of TgACS by VIGS assay in tulip petals delayed senescence, while over-expressed TgACS1 in tobacco promoted leaf senescence. Taken together, this study provides evidences to certify ethylene roles and TgACS functions during flower senescence in tulip.

Comparison of the Antifungal and Antiaflatoxigenic Potential of Liquid and Vapor Phase of Thymus vulgaris Essential Oil Against Aspergillus flavus

The antifungal and antiaflatoxigenic activity of Thymus vulgaris essential oil (EO) against Aspergillus flavus was evaluated over a range of concentrations in vapor- and liquid-phase contact tests. Total reduction in mycelial growth in the vapor- and liquid-phase tests was detected at EO concentrations of 20 and 400 μg/mL, respectively. Treatment with 10 μg/mL EO reduced aflatoxin production by 97.0 and 56.4% in the vapor- and liquid-phase tests, respectively. Greater inhibition of the expression of both fungal development-related genes (brlA, abaA, and wetA) and aflatoxin biosynthesis-related genes (aflR, aflD, and aflK) was also observed in the vapor-phase test. A substantial reduction in aflatoxin production was also observed in brown rice (72.7%) and white rice (18.0%). Our results indicate that the way this EO contacts fungal cells significantly affects its antifungal activity and that T. vulgaris EO in vapor phase might be a good strategy to control fungal contamination.

Comparative Analysis of Phenolic Compound Profiles, Antioxidant Capacities, and Expressions of Phenolic Biosynthesis-Related Genes in Soybean Microgreens Grown under Different Light Spectra.

Light-emitting diode (LED) based light sources, which can selectively and quantitatively provide different spectra, have been frequently applied to manipulate plant growth and development. In this study, the effects of different LED light spectra on the growth, phenolic compounds profile, antioxidant capacity, and transcriptional changes in genes regulating phenolic biosynthesis in soybean microgreens were investigated. The results showed that light illumination decreased the seedling length and yield but increased phenolic compound content. Blue light and ultraviolet-A (UV-A) induced significant increases in total phenolic and total flavonoid content, as compared with the white light control. Sixty-six phenolic compounds were identified in the soybean samples, of which isoflavone, phenolic acid, and flavonol were the main components. Ten phenolic compounds obtained from the orthogonal partial least-squares discriminant analysis (OPLS-DA) were reflecting the effect of light spectra. The antioxidant capacity was consistent with the phenolic metabolite levels, which showed higher levels under blue light and UV-A compared with the control. The highest transcript levels of phenolic biosynthesis-related genes were observed under blue light and UV-A. The transcript levels of GmCHI, GmFLS, and GmIOMT were also upregulated under far-red and red light. Taken together, our findings suggested that the application of LED light could pave a green and effective way to produce phenolic compound-enriched soybean microgreens with high nutritional quality, which could stimulate further investigations for improving plant nutritional value and should have a wide impact on maintaining human health.

Genome-wide analysis of transcription factors related to anthocyanin biosynthesis in carmine radish (Raphanus sativus L.) fleshy roots.

Carmine radish produced in Chongqing is famous for containing a natural red pigment (red radish pigment). However, the anthocyanin biosynthesis transcriptome and the expression of anthocyanin biosynthesis-related genes in carmine radish have not been fully investigated. Uncovering the mechanism of anthocyanin biosynthesis in the ‘Hongxin 1’ carmine radish cultivar has become a dominant research topic in this field. In this study, a local carmine radish cultivar named ‘Hongxin 1’ containing a highly natural red pigment was used to analyze transcription factors (TFs) related to anthocyanin biosynthesis during the dynamic development of fleshy roots. Based on RNA sequencing data, a total of 1,747 TFs in 64 TF families were identified according to their DNA-binding domains. Of those, approximately 71 differentially expressed transcription factors (DETFs) were commonly detected in any one stage compared with roots in the seedling stage (SS_root). Moreover, 26 transcripts of DETFs targeted by 74 miRNAs belonging to 25 miRNA families were identified, including MYB, WRKY, bHLH, ERF, GRAS, NF-YA, C2H2-Dof, and HD-ZIP. Finally, eight DETF transcripts belonging to the C2C2-Dof, bHLH and ERF families and their eight corresponding miRNAs were selected for qRT-PCR to verify their functions related to anthocyanin biosynthesis during the development of carmine radish fleshy roots. Finally, we propose a putative miRNA-target regulatory model associated with anthocyanin biosynthesis in carmine radish. Our findings suggest that sucrose synthase might act as an important regulator to modulate anthocyanin biosynthesis in carmine radish by inducing several miRNAs (miR165a-5p, miR172b, miR827a, miR166g and miR1432-5p) targeting different ERFs than candidate miRNAs in the traditional WMBW complex in biological processes.

A class I TGA transcription factor from Tripterygium wilfordii Hook.f. modulates the biosynthesis of secondary metabolites in both native and heterologous hosts

Class I TGA transcription factors (TFs) are known to participate in plant resistance responses, however, their regulatory functions in the biosynthesis of secondary metabolites were rarely revealed. In this study, a class I TGA TF, TwTGA1, from Tripterygium wilfordii Hook.f. was cloned and characterized. Overexpression of TwTGA1 in T. wilfordii Hook.f. cells increased the production of triptolide and two sesquiterpene pyridine alkaloids, which was further enhanced by methyl jasmonate (MeJA) treatment. RNA interference of TwTGA1 showed no significant effects on the production of these metabolites, indicating the existence of other TGA partner(s) with overlapping functions. Heterologous expression of TwTGA1 in tobacco By-2 cells promoted the biosynthesis of pyridine alkaloids. Under the elicitation of MeJA, the contents of nonpyrrolidine alkaloids further increased but not for nicotine. TwTGA1 could induce the expression of Putrescine N-methyltransferase (PMT) and N-methylputrescine oxidase 1 (MPO1) through binding to their promoters. Finally, transient expression of TwTGA1 in leaves of Catharanthus roseus changed both the profiles of vinca alkaloids (increased contents of serpentine and catharanthine, but decreased that of vinblastine) and the expressions of biosynthesis-related genes. The metabolic and transcriptional data indicated a relationship between jasmonic acid signaling pathway and the functions of TwTGA1.

Ursolic Acid Suppresses Cholesterol Biosynthesis and Exerts Anti-Cancer Effects in Hepatocellular Carcinoma Cells.

Abnormally upregulated cholesterol and lipid metabolism, observed commonly in multiple cancer types, contributes to cancer development and progression through the activation of oncogenic growth signaling pathways. Although accumulating evidence has shown the preventive and therapeutic benefits of cholesterol-lowering drugs for cancer management, the development of cholesterol-lowering drugs is needed for treatment of cancer as well as metabolism-related chronic diseases. Ursolic acid (UA), a natural pentacyclic terpenoid, suppresses cancer growth and metastasis, but the precise underlying molecular mechanism for its anti-cancer effects is poorly understood. Here, using sterol regulatory element (SRE)-luciferase assay-based screening on a library of 502 natural compounds, this study found that UA activates sterol regulatory element-binding protein 2 (SREBP2). The expression of cholesterol biosynthesis-related genes and enzymes increased in UA-treated hepatocellular carcinoma (HCC) cells. The UA increased cell cycle arrest and apoptotic death in HCC cells and reduced the activation of oncogenic growth signaling factors, all of which was significantly reversed by cholesterol supplementation. As cholesterol supplementation successfully reversed UA-induced attenuation of growth in HCC cells, it indicated that UA suppresses HCC cells growth through its cholesterol-lowering effect. Overall, these results suggested that UA is a promising cholesterol-lowering nutraceutical for the prevention and treatment of patients with HCC and cholesterol-related chronic diseases.

Improvement in lipid production in Monoraphidium sp. QLY-1 by combining fulvic acid treatment and salinity stress

The effects of the combined treatment of fulvic acid (FA) and salinity stress on lipid production in Monoraphidium sp. QLY-1 at multiple levels was investigated in this study. The results indicated that the highest lipid content (59.53%) in QLY-1 was achieved by combining FA treatment and salinity stress. Compared with the control group and FA addition alone, the group treated with both FA and salinity stress had increased contents of reactive oxygen species (ROS), antioxidases, and nitric oxide (NO). Additionally, the addition of FA enhanced the expression levels of mitogen-activated protein kinases (MAPKs) and key genes related to lipid biosynthesis in QLY-1 under salinity stress. Collectively, biochemical analyses indicated that ROS, NO, MAPK, expression of lipid biosynthesis-related genes and antioxidant systems were involved in the lipid biosynthesis pathways of QLY-1 under the combined treatment of FA and salinity stress.

The cotton GhWIN2 gene activates the cuticle biosynthesis pathway and influences the salicylic and jasmonic acid biosynthesis pathways

BackgroundMetabolic pathways are interconnected and yet relatively independent. Genes involved in metabolic modules are required for the modules to run. Study of the relationships between genes and metabolic modules improves the understanding of metabolic pathways in plants. The WIN transcription factor activates the cuticle biosynthesis pathway and promotes cuticle biosynthesis. The relationship between the WIN transcription factor and other metabolic pathways is unknown. Our aim was to determine the relationships between the main genes involved in cuticle biosynthesis and those involved in other metabolic pathways. We did this by cloning a cotton WIN gene, GhWIN2, and studying its influence on other pathways.ResultsAs with other WIN genes, GhWIN2 regulated expression of cuticle biosynthesis-related genes, and promoted cuticle formation. Silencing of GhWIN2 resulted in enhanced resistance to Verticillium dahliae, caused by increased content of salicylic acid (SA). Moreover, silencing of GhWIN2 suppressed expression of jasmonic acid (JA) biosynthesis-related genes and content. GhWIN2 positively regulated the fatty acid biosynthesis pathway upstream of the JA biosynthesis pathway. Silencing of GhWIN2 reduced the content of stearic acid, a JA biosynthesis precursor.ConclusionsGhWIN2 not only regulated the cuticle biosynthesis pathway, but also positively influenced JA biosynthesis and negatively influenced SA biosynthesis.

Two types of mutations in the HEUKCHEEM gene functioning in cucumber spine color development can be used as signatures for cucumber domestication.

The HEUKCHEEM gene plays an important role in spine color formation. A white spine occurs due to two mutations in HEUKCHEEM and is closely related to the regional distribution of these mutants. Mapping analysis revealed that the HEUKCHEEM gene is co-segregated with the B locus in the regulation of black spine color development in cucumber fruit. HEUKCHEEM induced the expression of the genes involved in the anthocyanin biosynthetic pathway, leading to the accumulation of anthocyanins in black spines. The transiently over-expressed HEUKCHEEM in cucumber and tobacco plants enhanced the expression of anthocyanin biosynthesis-related genes, leading to anthocyanin accumulation. However, two mutations-insertion of the 6994bp mutator-like transposable element (MULE) sequence into the second intron and one single-nucleotide polymorphism (SNP) of C to T in the second exon of HEUKCHEEM-were identified in white spines, leading to no accumulation of anthocyanin biosynthesis-related gene transcripts and anthocyanins. Furthermore, association analysis using 104 cucumber accessions with different geographical origins revealed that the types of mutations in HEUKCHEEM are strongly linked to geographical origins. The MULE insertion is found extensively in cucumbers with white spines in East Asia and Australia. However, cucumbers with white spines in other areas could be significantly influenced by a single SNP mutation. Our results provide fundamental information on spine color development in cucumber fruits and spine color-based cucumber breeding programs.

Role of calcium in regulating anthocyanin accumulation in ‘Manicure Finger’ grape berries

The objective of this study was to clarify the effects of calcium treatments on the anthocyanin accumulation of ‘Manicure Finger’ grape berries. Calcium treatments increased the calcium contents and enhanced the calmodulin activities in grapevine leaves and berries, upregulated the expression of the sugar transporter genes SUC12 and SUC27 in leaves, promoted the transport of photosynthetic products to berries, and increased the expression of anthocyanin biosynthesis-related genes in the grape berry skin. These results indicate that the application of exogenous calcium enhances anthocyanin accumulation in ‘Manicure Finger’ grape berries in the following two ways: (1) calcium promotes the transport of photosynthetic products to berries, thereby providing the basic material required for anthocyanin biosynthesis; (2) calcium induces anthocyanin biosynthesis by regulating the expression of relevant structural and regulatory genes. Our results will help researchers characterize the mechanism responsible for the calcium-mediated promotion of anthocyanin biosynthesis in grapevine and related plant species.

Papaya CpbHLH1/2 regulate carotenoid biosynthesis-related genes during papaya fruit ripening

The ripening of papaya is a physiological and metabolic process associated with accumulation of carotenoids, alternation of flesh color and flavor, which depending on genotype and external factors such as light and hormone. Transcription factors regulating carotenoid biosynthesis have not been analyzed during papaya fruit ripening. RNA-Seq experiments were implemented using different ripening stages of papaya fruit from two papaya varieties. Cis-elements in lycopene β-cyclase genes (CpCYC-B and CpLCY-B) were identified, and followed by genome-wide analysis to identify transcription factors binding to these cis-elements, resulting in the identification of CpbHLH1 and CpbHLH2, two bHLH genes. The expressions of CpbHLH1/2 were changed during fruit development, coupled with transcript increase of carotenoid biosynthesis-related genes including CpCYC-B, CpLCY-B, CpPDS2, CpZDS, CpLCY-E, and CpCHY-B. Yeast one-hybrid (Y1H) and transient expression assay revealed that CpbHLH1/2 could bind to the promoters of CpCYC-B and CpLCY-B, and regulate their transcriptions. In response to strong light, the results of elevated expression of carotenoid biosynthesis-related genes and the changed expression of CpbHLH1/2 indicated that CpbHLH1/2 were involved in light-mediated mechanisms of regulating critical genes in the carotenoid biosynthesis pathway. Collectively, our findings demonstrated several TF family members participating in the regulation of carotenoid genes and proved that CpbHLH1 and CpbHLH2 individually regulated the transcription of lycopene β-cyclase genes (CpCYC-B and CpLCY-B). This study yielded novel findings on regulatory mechanism of carotenoid biosynthesis during papaya fruit ripening.

Enhancement of lipid accumulation in Monoraphidium sp. QLY-1 by induction of strigolactone

In this study, the effects of strigolactone (SL) on the biomass, lipid content, biochemical properties, and gene transcription of Monoraphidium sp. QLY-1 were examined. The lipid content and lipid productivity increased by 61% and 55% in QLY-1 under 1 μM SL induction compared to the control group, respectively. SL also upregulated the levels of endogenous NO and Ca2+ and lipid biosynthesis gene transcription. Subsequently, the relationship between Ca2+ and nitric oxide (NO) in the regulation of cell growth and lipid accumulation of QLY-1 under SL induction conditions was analysed. An increase in endogenous Ca2+ regulated cell growth and lipid biosynthesis by modulating the levels of NO and lipid biosynthesis-related gene expression. Collectively, this study provided a valuable approach for biofuel production from microalgae under SL induction and demonstrated that there is crucial crosstalk between the Ca2+ and NO signalling in the manipulation of lipid biosynthesis in microalgae under SL treatment.

Aflatoxin B1 impairs leydig cells through inhibiting AMPK/mTOR-mediated autophagy flux pathway

Aflatoxin B1 (AFB1), a potential endocrine disrupter, has been shown to induce hepatotoxicity in animal models, but the effects of AFB1 on Leydig cell function are unclear. In this study, in vivo exposure to AFB1 at 15 and 150 μg/kg/day lowered serum testosterone (T), luteinizing hormone (LH), and follicle-stimulating hormone (FSH) levels, reduced Leydig cell number, and down-regulated the expression of testosterone biosynthesis-related genes. In vitro study showed that AFB1 (10 μM) significantly increased ROS levels, and decreased T production in Leydig cells by suppressing certain T-biosynthesis gene expressions. Moreover, AFB1 induced Leydig cell apoptosis through lowering pAMPK/AMPK ratio and increasing pmTOR/mTOR ratio, and then further up-regulating autophagy and apoptosis proteins, LC3, BECLIN 1, and BAX, as well as down-regulating autophagy flux protein P62 and anti-apoptosis protein BCL-2. AFB1-induced toxicity in Leydig cells was characterized by inhibiting T-biosynthesis gene expression, reducing Leydig cell number, promoting ROS production, and inducing cell apoptosis via suppressing AMPK/mTOR-mediated autophagy flux pathway.