Integrative physiological, metabolomic, and transcriptomic analysis reveals the drought responses of two apple rootstock cultivars.

BACKGROUND: Drought is considered the main environmental factor restricting apple production and thus the development of the apple industry. Rootstocks play an important role in enhancing the drought tolerance of apple plants. Studies of the physiology have demonstrated that 'ZC9-3' is a strong drought-resistant rootstock, whereas 'Jizhen-2' is a weak drought-resistant rootstock. However, the metabolites in these two apple rootstock varieties that respond to drought stress have not yet been characterized, and the molecular mechanisms underlying their responses to drought stress remain unclear. RESULTS: In this study, the physiological and molecular mechanisms underlying differences in the drought resistance of 'Jizhen-2' (drought-sensitive) and 'ZC9-3' (drought-resistant) apple rootstocks were explored. Under drought stress, the relative water content of the leaves was maintained at higher levels in 'ZC9-3' than in 'Jizhen-2', and the photosynthetic, antioxidant, and osmoregulatory capacities of 'ZC9-3' were stronger than those of 'Jizhen-2'. Metabolome analysis revealed a total of 95 and 156 differentially accumulated metabolites in 'Jizhen-2' and 'ZC9-3' under drought stress, respectively. The up-regulated metabolites in the two cultivars were mainly amino acids and derivatives. Transcriptome analysis revealed that there were more differentially expressed genes and transcription factors in 'ZC9-3' than in 'Jizhen-2' throughout the drought treatment. Metabolomic and transcriptomic analysis revealed that amino acid biosynthesis pathways play key roles in mediating drought resistance in apple rootstocks. A total of 13 metabolites, including L-α-aminoadipate, L-homoserine, L-threonine, L-isoleucine, L-valine, L-leucine, (2S)-2-isopropylmalate, anthranilate, L-tryptophan, L-phenylalanine, L-tyrosine, L-glutamate, and L-proline, play an important role in the difference in drought resistance between 'ZC9-3' and 'Jizhen-2'. In addition, 13 genes encoding O-acetylserine-(thiol)-lyase, S-adenosylmethionine synthetase, ketol-acid isomeroreductase, dihydroxyacid dehydratase, isopropylmalate isomerase, branched-chain aminotransferase, pyruvate kinase, 3-dehydroquinate dehydratase/shikimate 5-dehydrogenase, N-acetylglutamate-5-P-reductase, and pyrroline-5-carboxylate synthetase positively regulate the response of 'ZC9-3' to drought stress. CONCLUSIONS: This study enhances our understanding of the response of apple rootstocks to drought stress at the physiological, metabolic, and transcriptional levels and provides key insights that will aid the cultivation of drought-resistant apple rootstock cultivars. Especially, it identifies key metabolites and genes underlying the drought resistance of apple rootstocks.

Transcriptome and metabolome analyses reveal the regulatory role of MdPYL9 in drought resistance in apple.

BACKGROUND: The mechanisms by which the apple MdPYL9 gene mediates the response to drought stress remain unclear. Here, transcriptome and metabolome analyses of apple plants under drought were used to investigate the mechanisms by which MdPYL9 regulates the response to drought stress in apple. MdPYL9-overexpressed transgenic and non-transgenic apple histoculture seedlings were rooted, transplanted, and subjected to drought treatments to clarify the mechanisms underlying the responses of apples to drought stress through phenotypic observations, physiological and biochemical index measurements, and transcriptomic and metabolomic analyses. RESULTS: Under drought stress treatment, transgenic plants were less affected by drought stress than non-transgenic plants. Decreases in the net photosynthetic rate, stomatal conductance, and transpiration rate of transgenic apple plants were less pronounced in transgenic plants than in non-transgenic plants, and increases in the intercellular CO2 concentration were less pronounced in transgenic plants than in non-transgenic plants. The relative electrical conductivity and content of malondialdehyde, superoxide anion, and hydrogen peroxide were significantly lower in transgenic plants than in non-transgenic plants, and the chlorophyll content and activities of antioxidant enzymes (superoxide dismutase, peroxidase, and catalase) were significantly higher in transgenic plants than in non-transgenic plants. The number of differentially expressed genes (DEGs) involved in the response to drought stress was lower in transgenic plants than in non-transgenic plants, and the most significant and highly annotated DEGs in the transgenic plants were involved in the flavonoid biosynthesis pathway, and the most significant and highly annotated DEGs in control plants were involved in the phytohormone signal transduction pathway. The number of differentially accumulated metabolites involved in the response to drought stress was lower in transgenic plants than in non-transgenic plants, and up-regulated metabolites were significantly enriched in apigenin-7-O-glucoside in transgenic plants and in abscisic acid in non-transgenic plants. In the flavonoid biosynthetic pathway, the expression of genes encoding chalcone synthase (CHS) and chalcone isomerase (CHI) was more significantly down-regulated in non-transgenic plants than in transgenic plants, and the expression of the gene encoding 4-coumarate-CoA ligase (4CL) was more significantly up-regulated in transgenic plants than in non-transgenic plants, which resulted in the significant up-regulation of apigenin-7-O-glucoside in transgenic plants. CONCLUSIONS: The above results indicated that the over-expression of MdPYL9 increased the drought resistance of plants under drought stress by attenuating the down-regulation of the expression of genes encoding CHS and CHI and enhancing the up-regulated expression of the gene encoding 4CL, which enhanced the content of apigenin-7-O-glucoside.

Melatonin promotes the recovery of apple plants after waterlogging by shaping the structure and function of the rhizosphere microbiome.

The dynamics of the physiological adaptability of plants and the rhizosphere soil environment after waterlogging remain unclear. Here we investigated the mechanisms regulating plant condition and shaping of the rhizosphere microbiome in a pot experiment. In the experiment, we added melatonin to waterlogged plants, which promoted waterlogging relief. The treatment significantly enhanced photosynthesis and the antioxidant capacity of apple plants, and significantly promoted nitrogen (N) utilization efficiency by upregulating genes related to N transport and metabolism. Multiperiod soil microbiome analysis showed the dynamic effects of melatonin on the diversity of the microbial community during waterlogging recovery. Random forest and linear regression analyses were used to screen for potential beneficial bacteria (e.g., Azoarcus, Pseudomonas and Nocardioides) specifically regulated by melatonin and revealed a positive correlation with soil nutrient levels and plant growth. Furthermore, metagenomic analyses revealed the regulatory effects of melatonin on genes involved in N cycling in soil. Melatonin positively contributed to the accumulation of plant dry weight by upregulating the expression of nifD and nifK (N fixation). In summary, melatonin positively regulates physiological functions in plants and the structure and function of the microbial community; it promoted the recovery of apple plants after waterlogging stress.

Ubiquity of Synthetic Phenolic Antioxidants in Children's Cerebrospinal Fluid from South China: First Evidence for Their Penetration across the Blood-Cerebrospinal Fluid Barrier.

Synthetic phenolic antioxidants (SPAs) and relevant transformation products (TPs) are potentially neurotoxic pollutants to which humans are widely exposed. However, their penetration behavior across the brain barrier and associated exposure to the central nervous system (CNS) remain unknown. This study is the first to investigate a wide range of 30 SPAs and TPs, including emerging SPAs, in matched serum and cerebrospinal fluid (CSF) samples from children in Guangzhou, China. Sixty-two children of either sex aged <14 years with nonbloody CSF and complete clinical information were included. The findings demonstrated the ubiquitous occurrence of many SPAs and TPs, particularly BHT, 2,4-di-tert-butylphenol (DBP), AO 1010, AO 1076, BHT-Q, and BHT-quinol, not only in serum but also in the CSF. Median total concentrations of SPAs and TPs were up to 22.0 and 2.63 ng/mL in serum and 14.5 and 2.11 ng/mL in CSF, respectively. On calculating the penetration efficiencies across the blood-CSF barrier (BCSFB) (RCSF/serum, CCSF/Cserum) for selected SPAs and TPs, their RCSF/serum values (median 0.52-1.41) were highly related to their physicochemical properties, indicating that passive diffusion may be the potential mechanism of BCSFB penetration. In addition, the RCSF/serum values were positively correlated with the barrier permeability index RAlb (AlbuminCSF/Albuminserum), indicating that barrier integrity is an important determinant of BCSFB penetration. Overall, these results will improve our perception of human internal exposure to SPAs and lay a solid foundation for assessing the risk of CNS exposure to various SPAs.

Sexual behaviours and sexual health among middle-aged and older adults in Britain.

OBJECTIVES: Population-representative studies of the sexual health of middle-aged and older adults are lacking in ageing societies. This study aimed to identify latent patterns of sexual behaviours and health of people aged 45-74 years. METHODS: We conducted a latent class analysis of the National Attitudes and Sexual Lifestyles Survey (Natsal-3), a nationally representative survey conducted in Britain in 2011. RESULTS: Of the 5260 respondents aged 45-74 years, 48.86% of men and 44.91% of women belonged to the Content Caseys class who reported good sexual health. The Infrequent Indigos (30.94% of men, 44.38% of women) were characterised by a lack of sexual activity, reported some dissatisfaction, and were more likely to have a disability. The Low-Functioning Lees (11.65% of men, 8.41% of women) reported some more disability and had issues with sexual functioning and higher levels of distress. The Multiple-Partnered Morgans (8.62% of men, 2.30% of women) were characterised by a greater number of sexual partners and several risk behaviours. CONCLUSIONS: The use of these four classes can aid in improved targeting of tailored sexual health services to improve sexual function, sexual satisfaction, reduce distress and risky behaviours among middle-aged and older adults. These services should be inclusive of the disabled community.

Stakeholders' solutions to antiretroviral therapy interruption during the COVID-19 pandemic in China: a short report.

Obtaining antiretroviral therapy (ART) was a challenge for people living with HIV (PLHIV) in China during the COVID-19 outbreak. On 26 January 2020, the Chinese Center for AIDS/STD Control and Prevention issued a nationwide directive to relax restrictions on where and when PLHIV could refill ART. This qualitative study explored unexpected barriers under this directive and recommendations to improve future ART delivery. Between February 11 and February 15 2020, in-depth interviews of 4 groups of stake holders related to ART refilling (i.e., PLHIV, community-based organization employees, CDC staff, infectious disease physicians and nurses), were conducted via WeChat. Data were managed by NVivo 11.0 and transcripts were coded using thematic analysis. Sixty-two interviews were conducted. The main barriers to refilling ART included: (1) inconsistent documentation requirements to refill ART, (2) lack of specific protocols on ART refilling, (3) insufficient staffing, and (4) regimen verification and drug shortages. The most common recommendations to improve future ART delivery were: (1) to establish a nationwide system to distribute ART and (2) increase the number of pills delivered with each ART refill. Strengthening protocols and systems to refill ART and improving collaboration is key to preventing interruptions in ART among PLHIV during public health emergencies.

Prevalence of Novel and Traditional Synthetic Phenolic Antioxidants in Baby Food from China: A Dominant Pathway for Infant Exposure.

Synthetic phenolic antioxidants (SPAs) are a group of ubiquitous contaminants with multiple toxicities. However, current knowledge on the occurrence of SPAs in baby food and associated infant exposure is lacking. Herein, we analyzed three categories of baby food from China: infant formula, cereal, and puree, for a broad suite of 11 traditional and 19 novel SPAs. In addition to 11 traditional SPAs, up to 13 novel SPAs were detected in the baby food samples. The median concentrations of novel SPAs for infant formula, cereal, and puree were 604, 218, and 24.1 ng/g, respectively, surpassing those of traditional SPAs (53.4, 62.1, and 10.0 ng/g). The prevalent SPAs in the samples were butylated hydroxytoluene, 2,4-di-tert-butylphenol, pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (AO 1010), and octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate (AO 1076). Source analysis indicated that the prevalence of these four SPAs in baby food was associated with contamination of packaging materials, mechanical processing, or raw ingredients. Migration experiments demonstrated that contamination of plastic packaging constituted an important source. Exposure assessment suggested that there may be no appreciable health risk posed by the SPAs in baby food. Even so, baby food consumption was still a dominant pathway for infant exposure to SPAs, with a higher contribution than breast milk consumption, dust ingestion, dermal dust absorption, and air inhalation, which requires special attention.

Identification of Triazine UV Filters as an Emerging Class of Abundant, Ubiquitous Pollutants in Indoor Dust and Air from South China: Call for More Concerns on Their Occurrence and Human Exposure.

Triazine UV filters are an important class of UV filters, but knowledge on their environmental occurrence and human exposure remains largely unknown. In this study, we performed a targeted analysis of 17 emerging triazine UV filters in indoor dust and indoor air from South China based on a newly developed LC-MS/MS method. A total of 12 of the 17 emerging triazine UV filters were first positively detected in the dust and air samples. Ethylhexyl triazone (EHT) and bis-ethylhexyloxyphenol methoxyphenyl triazine (BEMT) were identified as the most abundant compounds. The median total concentrations of triazine UV filters reached 3860 ng/g in indoor dust and 1590 pg/m3 in indoor air. Gas-particle partitioning analysis showed that triazine UV filters were predominant in the particle phase in ambient air. Significant concentration correlations were observed among most triazine UV filters. The estimated daily intake of triazine UV filters through dust ingestion and air inhalation for toddlers under high-end exposure scenarios was up to 839 ng/kg bw/day, but a lack of toxic thresholds hampers accurate risk assessment. Our work highlights another emerging class of UV filters that significantly contribute to indoor chemical mixtures and expresses concerns over their occurrence and human exposure.

Ionomic Combined with Transcriptomic and Metabolomic Analyses to Explore the Mechanism Underlying the Effect of Melatonin in Relieving Nutrient Stress in Apple.

Nutrient stress harms plant growth and yield. Melatonin is a biologically active, multifunctional hormone that relieves abiotic stress in plants. Although previous studies have shown that melatonin plays an important role in improving nutrient-use efficiency, the mechanism of its regulation of nutrient stress remains unclear. In this study, melatonin was applied to apple plants under nutrient stress, and morphological indices, physiological and biochemical indices, and stomatal morphology were evaluated. The response of apple plants to nutrient deficiency and the melatonin mechanism to alleviate nutrient stress were analyzed by combining ionome, transcriptome, and metabolome. The results showed that exogenous melatonin significantly alleviated the inhibitory effect of nutritional stress on the growth of apple plants by regulating stomatal morphology, improving antioxidant enzyme activity, promoting ion absorption, and utilizing and changing the absorption and distribution of minerals throughout the plant. The transcriptome results showed that melatonin alleviated nutrient stress and promoted nutrient absorption and utilization by regulating glutathione metabolism and upregulating some metal ion transport genes. The metabolome results indicated that levels of oxalic acid, L-ascorbic acid, anthocyanins (cyanidin-3-O-galactoside), lignans (lirioresinol A and syringaresinol), and melatonin significantly increased after exogenous melatonin was applied to plants under nutrient stress. These differentially expressed genes and the increase in beneficial metabolites may explain how melatonin alleviates nutrient stress in plants.

Activation of Peracetic Acid with Lanthanum Cobaltite Perovskite for Sulfamethoxazole Degradation under a Neutral pH: The Contribution of Organic Radicals.

Advanced oxidation processes (AOPs) are effective ways to degrade refractory organic contaminants, relying on the generation of inorganic radicals (e.g., •OH and SO4•-). Herein, a novel AOP with organic radicals (R-O•) was reported to degrade contaminants. Lanthanum cobaltite perovskite (LaCoO3) was used to activate peracetic acid (PAA) for organic radical generation to degrade sulfamethoxazole (SMX). The results show that LaCoO3 exhibited an excellent performance on PAA activation and SMX degradation at neutral pH, with low cobalt leaching. Meanwhile, LaCoO3 also showed an excellent reusability during PAA activation. In-depth investigation confirmed CH3C(O)O• and CH3C(O)OO• as the key reactive species for SMX degradation in LaCoO3/PAA system. The presence of Cl- (1-100 mM) slightly inhibited the degradation of SMX in the LaCoO3/PAA system, whereas the addition of HCO3- (0.1-1 mM) and humic aid (1-10 mg/L) could significantly inhibit SMX degradation. This work highlights the generation of organic radicals via the heterogeneous activation of PAA and thus provides a promising way to destruct contaminants in wastewater treatment.

Transcriptome profiling of anthocyanin biosynthesis in the peel of 'Granny Smith' apples (Malus domestica) after bag removal.

BACKGROUND: Bagging is commonly used to enhance red pigmentation and thereby improve fruit quality of apples (Malus domestica). The green-skinned apple cultivar 'Granny Smith' develops red pigmentation after bagging removal, but the signal transduction pathways mediating light-induced anthocyanin accumulation in apple peel are yet to be defined. The aim of this study was to identify the mechanisms underpinning red pigmentation in 'Granny Smith' after bag removal based on transcriptome sequencing. RESULTS: The anthocyanin content in apple peel increased considerably after bag removal, while only trace amounts of anthocyanins were present in the peel of unbagged and bagged fruits. RNA sequencing identified 18,152 differentially expressed genes (DEGs) among unbagged, bagged, and bag-removed fruits at 0, 4, and 10 days after bag removal. The DEGs were implicated in light signal perception and transduction, plant hormone signal transduction, and antioxidant systems. Weighted gene co-expression network analysis of DEGs generated a module of 23 genes highly correlated with anthocyanin content. The deletion of - 2026 to - 1870 bp and - 1062 to - 964 bp regions of the MdMYB1 (LOC103444202) promoter induced a significant decrease in glucuronidase activity and anthocyanin accumulation in apple peel. CONCLUSIONS: Bagging treatment can induce red pigmentation in 'Granny Smith' via altering the expression patterns of genes involved in crucial signal transduction and biochemical metabolic pathways. The - 2026 to - 1870 bp and - 1062 to - 964 bp regions of the MdMYB1 promoter are essential for MdMYB1-mediated regulation of anthocyanin accumulation in the 'Granny Smith' apple cultivar. The findings presented here provide insight into the mechanisms of coloration in the peel of 'Granny Smith' and other non-red apple cultivars.

The effect of promoter methylation on MdMYB1 expression determines the level of anthocyanin accumulation in skins of two non-red apple cultivars.

BACKGROUND: Fruit color in apple (Malus domestica Borkh.) is ascribed mainly to the accumulation of anthocyanin pigments, and is an important trait for determining fruit market acceptance. Bagging is a commonly used treatment to enhance the red pigmentation in apple skin. The MdMYB1 transcription factor gene plays an important role in the biosynthesis of anthocyanin in apple after bag removal, but little is known about how MdMYB1 transcription is regulated. RESULTS: In this study, we investigated pigmentation in the non-red skinned cultivars 'Granny Smith' and 'Golden Delicious' after bag removal. The fruit skins of the two cultivars showed red/pink pigmentation after bag treatment. Transcript levels of MdMYB1, the master regulator of anthocyanin biosynthesis in apple, increased, and showed a correlation with anthocyanin content in both cultivars after bag removal. The MdMYB1 genomic sequences were compared in the two cultivars, which showed that the green-fruited cultivar 'Granny Smith' harbors the MdMYB1-1 and MdMYB1-2 alleles, while the yellow-fruited cultivar 'Golden Delicious' harbors only MdMYB1-2. A comparison of methylation levels in the 2 kb region upstream of the MdMYB1 ATG between the bag-treated fruits after removal from the bags and the unbagged fruits showed a correlation between hypomethylation and the red-skin phenotype in 'Granny Smith'. Moreover, 'Granny Smith' fruits responded to treatment with 5-aza-2'-deoxycytidine, an inducer of DNA demethylation. An investigation of the MdMYB1 promoter in 'Granny Smith' showed reduced methylation in the regions - 2026 to - 1870 bp, - 1898 to - 1633 bp, and - 541 to - 435 bp after bag removal and 5-aza-2'-deoxycytidine treatments. CONCLUSIONS: Differences in anthocyanin levels between 'Granny Smith' and 'Golden Delicious' can be explained by differential accumulation of MdMYB1-specific mRNA. Different levels of MdMYB1 transcripts in the two cultivars are associated with methylation levels in the promoter region. Hypomethylation of the MdMYB1 promoter is correlated with the formation of red pigmentation in 'Granny Smith' fruit skins. As a result, red pigmentation in Granny Smith' was more intense than in 'Golden Delicious' fruits after bag removal.

Mapping QTLs for water-use efficiency reveals the potential candidate genes involved in regulating the trait in apple under drought stress.

BACKGROUND: Improvement of water-use efficiency (WUE) can effectively reduce production losses caused by drought stress. A better understanding of the genetic determination of WUE in crops under drought stress has great potential value for developing cultivars adapted to arid regions. To identify the genetic loci associated with WUE and reveal genes responsible for the trait in apple, we aim to map the quantitative trait loci (QTLs) for carbon isotope composition, the proxy for WUE, applying two contrasting irrigating regimes over the two-year experiment and search for the candidate genes encompassed in the mapped QTLs. RESULTS: We constructed a high-density genetic linkage map with 10,172 markers of apple, using single nucleotide polymorphism (SNP) markers obtained through restriction site-associated DNA sequencing (RADseq) and a final segregating population of 350 seedlings from the cross of Honeycrisp and Qinguan. In total, 33 QTLs were identified for carbon isotope composition in apple under both well-watered and drought-stressed conditions. Three QTLs were stable over 2 years under drought stress on linkage groups LG8, LG15 and LG16, as validated by Kompetitive Allele-Specific PCR (KASP) assays. In those validated QTLs, 258 genes were screened according to their Gene Ontology functional annotations. Among them, 28 genes were identified, which exhibited significant responses to drought stress in 'Honeycrisp' and/or 'Qinguan'. These genes are involved in signaling, photosynthesis, response to stresses, carbohydrate metabolism, protein metabolism and modification, hormone metabolism and transport, transport, respiration, transcriptional regulation, and development regulation. They, especially those for photoprotection and relevant signal transduction, are potential candidate genes connected with WUE regulation in drought-stressed apple. CONCLUSIONS: We detected three stable QTLs for carbon isotope composition in apple under drought stress over 2 years, and validated them by KASP assay. Twenty-eight candidate genes encompassed in these QTLs were identified. These stable genetic loci and series of genes provided here serve as a foundation for further studies on marker-assisted selection of high WUE and regulatory mechanism of WUE in apple exposed to drought conditions, respectively.

The mitigation effects of exogenous melatonin on replant disease in apple.

Melatonin mediates many physiological processes in plants. The problem of apple replant disease is unsolved. Our study objectives were to evaluate the regulatory effect of melatonin on plant resistance to this challenge and investigate the preliminary mechanism by which melatonin helps alleviate the effects of this disease. Two-year-old trees of "Fuji" apple (Malus domestica), grafted onto rootstock M.26, were grown in "replant" soil for 6 months in the absence or presence of a 200 µmol/L melatonin supplement. The addition of melatonin to the soil significantly increased the rates of plant growth and net photosynthesis and chlorophyll concentrations under replant conditions. This molecule elevated the levels of K in leaves and roots and enhanced the activity of soil enzymes. Such supplementation also changed the composition of the bacterial and fungal communities in the soil. We concluded that the application of melatonin to a replant soil can protect their chloroplasts from oxidative damage and release the apple root from membrane damage, and also lead to increased soil enzyme activity and soil quality while altering the composition of bacterial and fungal communities. These changes can then promote seedling growth, stimulate photosynthesis, and elevate K levels, thereby alleviating the effects of apple replant disease.

Transcriptome Profiling Reveals Transcriptional Regulation by DNA Methyltransferase Inhibitor 5-Aza-2'-Deoxycytidine Enhancing Red Pigmentation in Bagged "Granny Smith" Apples (Malus domestica).

The red color of apples (Malus domestica) is an attractive trait for consumers. The green skinned "Granny Smith" cultivar develops red pigmentation after bagging treatment. DNA methylation plays an important role in various developmental processes in plants. To explore the possible functions of DNA methylation in the pigmentation of bagged "Granny Smith" apples, we first analyzed the anthocyanin content of fruit skin following treatment with the DNA methyltransferase inhibitor 5-aza-2'-deoxycytidine (5-aza-dC). The results revealed an increase in anthocyanin content in bagged fruits following 5-aza-dC treatment, while no anthocyanins were detected in unbagged fruits. In addition, 8482 differentially expressed genes between 5-aza-dC-treated and control groups were identified in bagged fruits by RNA sequencing, including genes encoding transcription factors, enzymes related to anthocyanin accumulation, and methylases. Changes in the expression of these genes may be responsible for 5-aza-dC-induced red pigmentation in bagged fruits of "Granny Smith". The findings provide novel evidence for the involvement of DNA methylation in the red pigmentation of non-red-skinned apples.

Effects of Exogenous Melatonin on Methyl Viologen-Mediated Oxidative Stress in Apple Leaf.

Oxidative stress is a major source of damage of plants exposed to adverse environments. We examined the effect of exogenous melatonin (MT) in limiting of oxidative stress caused by methyl viologen (MV; paraquatin) in apple leaves (Malus domestica Borkh.). When detached leaves were pre-treated with melatonin, their level of stress tolerance increased. Under MV treatment, melatonin effectively alleviated the decrease in chlorophyll concentrations and maximum potential Photosystem II efficiency while also mitigating membrane damage and lipid peroxidation when compared with control leaves that were sprayed only with water prior to the stress experiment. The melatonin-treated leaves also showed higher activities and transcripts of antioxidant enzymes superoxide dismutase, peroxidase, and catalase. In addition, the expression of genes for those enzymes was upregulated. Melatonin-synthesis genes MdTDC1, MdT5H4, MdAANAT2, and MdASMT1 were also upregulated under oxidative stress in leaves but that expression was suppressed in response to 1 mM melatonin pretreatment during the MV treatments. Therefore, we conclude that exogenous melatonin mitigates the detrimental effects of oxidative stress, perhaps by slowing the decline in chlorophyll concentrations, moderating membrane damage and lipid peroxidation, increasing the activities of antioxidant enzymes, and changing the expression of genes for melatonin synthesis.

Automated Quantification of the Impact of Defects on the Mechanical Behavior of Deoxyribonucleic acid Origami Nanoplates.

Deoxyribonucleic acid (DNA) origami is a method for the bottom-up self-assembly of complex nanostructures for applications, such as biosensing, drug delivery, nanopore technologies, and nanomechanical devices. Effective design of such nanostructures requires a good understanding of their mechanical behavior. While a number of studies have focused on the mechanical properties of DNA origami structures, considering defects arising from molecular self-assembly is largely unexplored. In this paper, we present an automated computational framework to analyze the impact of such defects on the structural integrity of a model DNA origami nanoplate. The proposed computational approach relies on a noniterative conforming to interface-structured adaptive mesh refinement (CISAMR) algorithm, which enables the automated transformation of a binary image of the nanoplate into a high fidelity finite element model. We implement this technique to quantify the impact of defects on the mechanical behavior of the nanoplate by performing multiple simulations taking into account varying numbers and spatial arrangements of missing DNA strands. The analyses are carried out for two types of loading: uniform tensile displacement applied on all the DNA strands and asymmetric tensile displacement applied to strands at diagonal corners of the nanoplate.

Exogenous melatonin improved potassium content in Malus under different stress conditions.

Melatonin mediates many physiological processes in plants. We investigated its role in regulating growth, potassium uptake, and root system architecture under three types of stress: salinity or a deficiency of all nutrients in Malus hupehensis Rehd., as well as a K deficiency in Malus rockii Rehd. Each treatment caused a reduction in growth rates and disrupted the absorption of potassium. However, pretreatment with 0.1 mmol/L melatonin significantly alleviated such inhibitions. The addition of melatonin also upregulated genes for antioxidant enzymes involved in the ascorbate-glutathione cycle (MdcAPX, MdDHAR1, MdDHAR2, MdMDHAR, and MdcGR) and helped decrease the accumulation of H2 O2 while improving the expression of K transporters and genes for the CBL1-CIPK23 pathway. These results indicated that melatonin can regulate the ROS signal and activate the CBL1-CIPK23 pathway to regulate the expression of a potassium channel protein gene, thereby promoting the absorption of potassium ions. Our findings demonstrate that inducing melatonin production is an important mechanism for plant defenses that can serve as a platform for possible applications in agricultural or related fields of research.

Two new pyrrolosesquiterpenes produced by a Streptomyces species.

Two new pyrrolosesquiterpenes, 1 and 2, were isolated from cultures of the soil actinomycete Streptomyces sp. Hd7-21. The structures of these compounds were established as (2Z,4E,9E)-6,7,11-trihydroxy-3,7,11-trimethyl-1-(1H-pyrrol-2-yl)dodeca-2,4,9-trien-1-one (1) and (2Z,4E)-5-{3-[(2E)-4-hydroxy-4-methylpent-2-en-1-yl]-3-methyloxiran-2-yl}-3-methyl-1-(1H-pyrrol-2-yl)penta-2,4-dien-1-one (2) by extensive spectroscopic analyses including MS, and 1D- and 2D-NMR data. Their cytotoxic activities against a panel of human cancer cell lines were evaluated.

Structural elucidation and NMR assignments of two new pyrrolosesquiterpenes from Streptomyces sp. Hd7-21.

Two new pyrrolosesquiterpenes were isolated from cultures of the soil actinomycete Streptomyces sp. Hd7-21. The structures of these compounds were elucidated by extensive spectroscopic analyses including MS and 1D and 2D NMR data. Their cytotoxic activity against a panel of human cancer cell lines were biologically evaluated.