Hydroxytryptophan biosynthesis by a family of heme-dependent enzymes in bacteria.

Hydroxytryptophan serves as a chemical precursor to a variety of bioactive specialized metabolites, including the human neurotransmitter serotonin and the hormone melatonin. Although the human and animal routes to hydroxytryptophan have been known for decades, how bacteria catalyze tryptophan indole hydroxylation remains a mystery. Here we report a class of tryptophan hydroxylases that are involved in various bacterial metabolic pathways. These enzymes utilize a histidine-ligated heme cofactor and molecular oxygen or hydrogen peroxide to catalyze regioselective hydroxylation on the tryptophan indole moiety, which is mechanistically distinct from their animal counterparts from the nonheme iron enzyme family. Through genome mining, we also identify members that can hydroxylate the tryptophan indole ring at alternative positions. Our results not only reveal a conserved way to synthesize hydroxytryptophans in bacteria but also provide a valuable enzyme toolbox for biocatalysis. As proof of concept, we assemble a highly efficient pathway for melatonin in a bacterial host.

Chemodiversity of Dissolved Organic Matter Is Governed by Microbial Biogeography in Inland Waters.

Dissolved organic matter (DOM) is crucial for the carbon biogeochemical cycle and has a close link with microbiome in aquatic ecosystems; however, the causal relationship between DOM and microbial diversity in inland waters is not very clear so far. Therefore, a national survey of China's inland waters was conducted, and the DOM chemical composition and microbial community composition were determined by Fourier transform ion cyclotron resonance mass spectrometry and high-throughput sequencing to clarify the abovementioned question. Here, we found that DOM chemodiversity was governed by microbial community assembly in inland waters, not vice versa. Under the control of microbial biogeography, DOM chemodiversity showed a clear geographical distribution difference. Water DOM chemodiversity was mainly constrained by bacterial and archaeal community composition, whereas sediment DOM chemodiversity was mainly controlled by eukaryotic and fungal community composition. In addition, the sediment DOM chemical composition was also affected by the interaction of different microbial groups between waters and sediments. The study is the first to clarify the causal relationship and proposes a microbial regulatory mechanism on the geographical distribution pattern of DOM chemodiversity, thus further deepening the understanding of the DOM biogeochemical cycle.

The effect of hydration and dehydration on the conformation, assembling behavior and photoluminescence of PBLG.

Hydration and dehydration play crucial roles in hydrophobic effects (HEs) and are yet to be understood. Poly(γ-benzyl-L-glutamate) (PBLG) homopolymers in THF/water with various water contents were investigated. We discovered that PBLG was hydrated at low water contents and adopted a helical conformation. The chain became dehydrated with increasing water content, which converted the PBLG100 helix to a PPII-helix. The variation in the conformation resulted in an alteration of the self-assembled morphologies from fibers to particles. For PBLG12 with a shorter chain, the chain underwent an α-to-ß transition in the conformation due to dehydration as the water content increased, and correspondingly the morphologies varied from tapes to helical ribbons, and eventually to toroids at a higher water content. We also observed that this α-to-ß transition is accompanied by an increase in intensity of the fluorescence, which is attributed to the through-space-conjugation of tightly packed phenyl groups within the ß-sheet. The discovered effect of hydration and dehydration on the PBLG chain conformation, self-assembling behavior and optical function is essential for the innovation of polypeptide materials and understanding of water-mediated biological systems.

Moving out but not for the better: Health consequences of interprovincial rural-urban migration in China.

Using panel data from a survey conducted by the Research Center for Rural Economy, this study overcomes the selection bias associated with most health status measures by incorporating dialect proximity as an instrumental variable to evaluate the causal effects of interprovincial migration on individuals' health status in China. The results indicate that, compared to an absorbed category, which includes intraprovincial migration and non-migration, interprovincial migration worsens health (measured by the self-reported health status score) by 3%. It is also found that, compared to intraprovincial migrants, interprovincial migrants are more likely to report a lower SHS score, whereas the health effect differences between interprovincial migrants and non-migrants are insignificant. The study identifies two potential mechanisms that explain this result: (i) The increase in income following migration may improve interprovincial migrants' health, and (ii) the exposure to hazardous working environments worsens health to a significant extent. This finding is also linked to the following gender-related finding: Compared to women, men are more likely to be employed in heavy industries with hazardous working environments; the negative effects of interprovincial migration on the health status are stronger for men than for women migrants, suggesting that the industry effect dominates.

Ecological function-oriented vegetation protection and restoration strategies in China's Loess Plateau.

Potential natural vegetation (PNV) can provide a reference for vegetation protection and restoration. Previous studies often used PNV patterns as a reference; however, they ignored PNV ecological functions, impeding the establishment of function-oriented vegetation protection and restoration plans. To address this issue, this study used Loess Plateau of China as a case study to propose an ecological function-oriented vegetation protection and restoration framework based on PNV patterns and ecological functions. The results showed that PNV patterns, ecological functions, and their synergistic and trade-off relationships represented distinct spatial differences that would be largely influenced by climate change. This suggested that vegetation protection and restoration should be adapted to climate change. The protection and potential restoration regions for actual forest and grass were detected based on the stable PNV regions. Approximately 34.5%-41.4% of actual forest and 81.2%-82.3% of actual grass should be protected. Further, 13.9%-16.2% of actual forest and 14.7%-15.2% of actual grass have the potential to be restored to grass and forest, respectively, and lastly, the priority regions of forest and grass protection and potential restoration were determined according to a composite ecological functions index. Moreover, forest protection should be prioritized, followed by forest potential restoration, grass potential restoration, and grass protection. These results would be conducive to forest and grass protection and restoration of the Loess Plateau. The proposed framework is applicable to other regions of the world for developing vegetation protection and restoration strategies.

Regulating the morphology and size of homopolypeptide self-assemblies via selective solvents.

It remains a great challenge to control the morphology and size of self-assembled homopolypeptide aggregates. In this work, rod-like micelles including spindles and cylinders were prepared by a solution self-assembly of poly(γ-benzyl-l-glutamate) (PBLG) homopolypeptides with different degrees of polymerization, in which their size was controlled precisely by tuning the ratio of water/methanol in selective cosolvents. The length of the rod-like micelles increased with an increasing amount of methanol in the selective cosolvents, which was confirmed using the combination of SEM, TEM and AFM. The self-assembly mechanism of PBLG in selective cosolvents was investigated by using complementary Fourier transform infrared (FT-IR), circular dichroism (CD) and low-field NMR analyses. It was found that the shrinkage and swelling of PBLG chains play important roles in the self-assembly process. The obtained results may provide a guideline for the study of regulating the assembled aggregate sizes.

Non-homologous chromosome pairing during meiosis in haploid Brassica rapa.

KEY MESSAGE: Cytological observations of chromosome pairing showed that evolutionarily genome duplication might reshape non-homologous pairing during meiosis in haploid B. rapa. A vast number of flowering plants have evolutionarily undergone whole genome duplication (WGD) event. Typically, Brassica rapa is currently considered as an evolutionary mesohexaploid, which has more complicated genomic constitution among flowering plants. In this study, we demonstrated chromosome behaviors in haploid B. rapa to understand how meiosis proceeds in presence of a single homolog. The findings showed that a diploid-like chromosome pairing was generally adapted during meiosis in haploid B. rapa. Non-homologous chromosomes in haploid cells paired at a high-frequency at metaphase I, over 50% of examined meiocytes showed at least three pairs of bivalents then equally segregated at anaphase I during meiosis. The fluorescence immunostaining showed that the cytoskeletal configurations were mostly well-organized during meiosis. Moreover, the expressed genes identified at meiosis in floral development was rather similar between haploid and diploid B. rapa, especially the expression of known hallmark genes pivotal to chromosome synapsis and homologous recombination were mostly in haploid B. rapa. Whole-genome duplication evolutionarily homology of genomic segments might be an important reason for this phenomenon, which would reshape the first division course of meiosis and influence pollen development in plants.

Enzymatic Tailoring in Luzopeptin Biosynthesis Involves Cytochrome†P450-Mediated Carbon-Nitrogen Bond Desaturation for Hydrazone Formation.

Luzopeptins and related decadepsipeptides are bisintercalator nonribosomal peptides featuring rare acyl-substituted tetrahydropyridazine-3-carboxylic acid (Thp) subunits that are critical to their biological activities. Herein, we reconstitute the biosynthetic tailoring pathway in luzopeptin A biosynthesis through in vivo genetic and in vitro biochemical approaches. Significantly, we revealed a multitasking cytochrome P450 enzyme that catalyzes four consecutive oxidations including the highly unusual carbon-nitrogen bond desaturation, forming the hydrazone-bearing 4-OH-Thp residues. Moreover, we identified a membrane-bound acyltransferase that likely mediates the subsequent O-acetylation extracellularly, as a potential self-protective strategy for the producer strain. Further genome mining of novel decadepsipeptides and an associated P450 enzyme have provided mechanistic insights into the P450-mediated carbon-nitrogen bond desaturation. Our results not only reveal the molecular basis of pharmacophore formation in bisintercalator decadepsipeptides, but also expand the catalytic versatility of P450 family enzymes.

The cotton endocycle-involved protein SPO11-3 functions in salt stress via integrating leaf stomatal response, ROS scavenging and root growth.

The SPORULATION 11 (SPO11) proteins are among eukaryotic the topoisomerase VIA (Topo VIA) homologs involved in modulating various important biological processes, such as growth, development and stress response via endoreduplication in plants, but the underlying mechanism response to stress remains largely unknown under salt treatment. Here, we attempted to characterize a homolog of TOP VIA in upland cotton (Gossypium hirsutum L.), designated as GhSPO11-3. The silencing of GhSPO11-3 in cotton plants resulted in a dwarf phenotype with a failure of cell endoreduplication and a phase shift in the ploidy levels. The GhSPO11-3-silenced plants also showed substantial changes including accumulated malondialdehyde, significantly reduced chlorophyll and proline contents and decreased antioxidative enzyme activity after salt treatment. In addition, transgenic Arabidopsis lines overexpressing GhSPO11-3 accelerated both leaf and root growth with cell expansion and endopolyploidy. Both leaf stomatal density and aperture were markedly decreased, and the transgenic Arabidopsis lines were more tolerant with expression of stress-responsive genes under salinity stress. Furthermore, consistent with the reduced reactive oxygen species (ROS), the expression of ROS scavenging-related genes was largely reinforced, and antioxidant enzyme activities were accordingly significantly enhanced in transgenic Arabidopsis lines under salt stress. In general, these results indicated that GhSPO11-3 likely respond to salt stress by positively regulating root growth, stomatal response, ROS production and the expression of stress-related genes to cope with adverse conditions in plants.

Curcumin protects cortical neurons against oxygen and glucose deprivation/reoxygenation injury through flotillin-1 and extracellular signal-regulated kinase1/2 pathway.

In this study, we provided evidence that curcumin could be a promising therapeutic agent for ischemic stroke by activating neuroprotective signaling pathways. Post oxygen and glucose deprivation/reoxygenation (OGD/R), primary mouse cortical neurons treated with curcumin exhibited a significant decrease in cell death, LDH release and enzyme caspase-3 activity under OGD/R circumstances, which were abolished by flotillin-1 downregulation or extracellular signal-regulated kinase (ERK) inhibitor. Moreover, flotillin-1 knockdown led to suppression of curcumin-mediated ERK phosphorylation under OGD/R condition. Based on these findings, we concluded that curcumin could confer neuroprotection against OGD/R injury through a novel flotillin-1 and ERK1/2 pathway.

Stepwise degradation of organic matters driven by microbial interactions in China΄s coastal wetlands: Evidence from carbon isotope analysis.

The microbial "unseen majority" as drivers of carbon cycle represent a significant source of uncertain climate change. To comprehend the resilience of life forms on Earth to climate change, it is crucial to incorporate knowledge of intricate microbial interactions and their impact to carbon transformation. Combined with carbon stable isotope analysis and high-throughput sequencing technology, the underlying mechanism of microbial interactions for organic carbon degradation has been elucidated. Niche differentiation enabled archaea to coexist with bacteria mainly in a cooperative manner. Bacteria composed of specialists preferred to degrade lighter carbon, while archaea were capable of utilizing heavier carbon. Microbial resource-dependent interactions drove stepwise degradation of organic matter. Bacterial cooperation directly facilitated the degradation of algae-dominated particulate organic carbon, while competitive feeding of archaea caused by resource scarcity significantly promoted the mineralization of heavier particulate organic carbon and then the release of dissolved inorganic carbon. Meanwhile, archaea functioned as a primary decomposer and collaborated with bacteria in the gradual degradation of dissolved organic carbon. This study emphasized microbial interactions driving carbon cycle and provided new perspectives for incorporating microorganisms into carbon biogeochemical models.

Mental health penalties of having a child: findings from the China family panel studies.

In recent years, the birth rate in China has rapidly declined. While much research has been done on the penalties in earnings that women incur when they fall behind men in the labor market due to childbirth, there has been little to no research on the mental health effects. This study addresses the gap in current literature by examining the mental health penalties that women experience after having a child in comparison to men. We applied econometric modeling to data collected from China Family Panel Studies (CFPS) and found that women experienced a significant, immediate, and long-run decline (4.3%) in life satisfaction after their first child, while men were unaffected. We also found that women experienced a significant increase in depression after their first child. This suggests mental health penalties since the mental health risk proxied by these two measurements is only significant for women. This is likely related to child penalties in labor market performance and childbirth-related physical health issues. When countries adopt multiple tools to stimulate the birth rate for economic growth, they must consider the implicit burden on women-especially the long-term negative effects on mental health.

Living with particles: Disclosure of pollution information, individual responses, and health consequences.

Drawing on a panel dataset-the China Health and Retirement Longitudinal Survey (CHARLS)-and other city- and individual-level datasets, this study examines the causal impact of pollution information disclosure on individual outdoor activities and the health status of the middle-aged and elderly. Using city-level variations in disclosure timing, we found that the adoption of pollution information disclosure (PID) significantly reduces the probability of outdoor exercise, especially for those living in more polluted cities. This occurs mainly through enhanced awareness of environmental pollution, particularly for those who are more educated. However, the adoption of PID does not lead to an improvement in health status.

Does money matter for child nutrition? Exploration of a preschool nutrition program in rural South-Central China.

OBJECTIVES: The aim of this study was to examine the relationship between poverty and children's nutritional outcomes. METHODS: Drawing on a 2018 survey of the preschool nutrition program conducted in the Xiangxi Autonomous Prefecture, Hunan Province, China, we applied propensity score matching to estimate the average treatment effects on the treated children. RESULTS: The most striking result was that although poverty is often used as predictive of poor childhood nutrition, this effect was only significant for weight-for-age z-score and height-for-age z-score, but not for other nutritional indicators, cognition, or social emotional indexes. The results varied using different measures of poverty. The weak linkage between poverty and children's nutritional outcomes was confirmed by a series of robustness checks by changing the covariates for matching, adopting other matching methods, using bootstrapping standard errors, and building on machine learning tools. CONCLUSIONS: A single tool of small money transfer would have limited effects, but considerable income increases that lift the poor out of poverty are important for the poor. Additionally, a mixed tool of financial support and nutritional knowledge may lead to better outcomes, especially for those living above the poverty line.

Do cooperatives exclude small-scale farming households? Evidence from Fuchuan County, Guangxi Province.

The exclusion, or otherwise, of small-scale farmers by cooperatives determines whether they can be well engaged in the grand strategy of agricultural modernization. By identifying the exclusion pattern of cooperatives and using the field research data on farmers in Fuchuan, Guangxi, this study finds that cooperatives tend to screen their members via both explicit and implicit exclusion and that small-scale farmers are more likely to be excluded. The theoretical analysis conducted in this study reveals that excluding small-scale farmers is a rational choice made by cooperatives to pursue efficiency in the context of organizational form variation. Furthermore, cooperatives' organizational form variation and their decisions to exclude small-scale farmers are endogenous, thereby suggesting that cooperatives in China may become unions of rural elites. During the exploration of using cooperatives as a carrier to involve small-scale farmers in agricultural modernization, the phenomenon of cooperatives' exclusion of small-scale farmers needs to be highly emphasized.

Age and Sex Differences Among Mildly Symptomatic and Asymptomatic Patients with Omicron Infection in 2022 in Shanghai, China.

Background: An epidemic of the Omicron variant of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) began in March 2022, and over 600,000 cases were confirmed until early May 2022 in Shanghai, China. Data on Omicron infections are available in other countries, but the clinical features of patients in the Chinese population, especially in Shanghai, are still lacking. We collected data from a subset of asymptomatic and mildly ill patients to learn about the age and sex disparity of Omicron infection based on changes in cycle threshold values. Methods: The basic information of 325 patients who were consecutively admitted to the Shanghai Geriatrics Center was collected through medical records, and patients were tested for viral nucleic acid carriage using nasal swab samples during hospitalization. SAS 9.4 was used for data analysis, and a p value < 0.05% was considered statistically significant. Results: Among the 325 included patients, 58.8% were males, with a mean age of 47.2 years and 13.6 days of hospitalization on average. The average number of nucleic acid tests among female patients was 4.7, which was higher than that among male patients (4.1). The median value of the slope for cycle threshold (Ct) changes in the nucleic acid detection (NAD) test was 1.4. Logistic regression indicated that the proportion of slope for Ct changes >1.5 was slightly higher among male patients than among female patients (odds ratio (OR) = 1.06, 95% confidence interval (CI): 0.68-1.66), and patients aged <45 years and 45-59 years had a higher proportion of slope for Ct changes >1.5 than patients aged ≥60 years. Ct values were more variable in the early stages of infection and stabilized in the later stages of infection. Conclusion: Among patients with mild illness or asymptomatic infection, the Ct value is a good, timely, and cost-effective method to reflect the recovery progress of patients. The slope of Ct changes was steeper among younger patients and male patients, which indicates faster disease recovery.

Integrated cytological and transcriptomic analysis reveals insights into pollen fertility in newly synthetic Brassica allohexaploids.

Trigenomic Brassica allohexaploids (AABBCC, 2n = 6x = 54) have great potential in oilseed breeding and genetic diversity. However, Brassica allohexaploids do not exist naturally, and the underlying mechanism regulating pollen fertility in artificially synthesized Brassica allohexaploids is still unclear. In this study, synthetic Brassica allohexaploids were produced by crossing allotetraploid B. carinata (BBCC, 2n = 4x = 34) and diploid B. rapa (AA, 2n = 2x = 20), followed by chromosome doubling. The results showed that the pollen fertility was significantly reduced and the pollen structures were mostly distorted, but the nursing anther tapetum developed normally in the synthetic Brassica allohexaploids. Furthermore, the data showed that the meiotic events occurred irregularly with uneven chromosome segregation and microspore development appeared mostly abnormal. Transcription analysis showed that the upregulation of genes related to the negative regulation of flower development and the downregulation of genes related to chromosome segregation might play an essential role in reduction of pollen fertility in the Brassica allohexaploids. In conclusion, this study elucidated the related mechanisms affecting pollen fertility during male gametophytic development at the cytological and transcriptomic levels in the newly synthesized Brassica allohexaploids.

To buy or not buy food online: The impact of the COVID-19 epidemic on the adoption of e-commerce in China.

Drawing on a recent online survey combined with city-level data, this paper examines the impact of the COVID-19 on consumers' online food purchase behavior in the short term. To address the potential endogeneity issues, we adopt an instrumental variable (IV) strategy, using the distance from the surveyed city to Wuhan as the instrumental variable. We show that our IV method is effective in minimizing potential bias. It is found that the share of confirmed COVID-19 cases increases the possibility of consumers purchasing food online. This is more likely to be the case for young people having a lower perceived risk of online purchases and living in large cities. Despite some limitations, this paper has policy implications for China and other countries that have been influenced by the COVID-19 epidemic. Specifically, government support and regulation should focus on (i) ensuring the safety of food sold on the internet, (ii) protecting the carrier from becoming infected, and (iii) providing financial support to the poor since they may have difficulties in obtaining access to food living in small cities. Moreover, how to help those who are unable to purchase food online because of their technical skills (e.g., the elderly who are not familiar with smart phones or the internet) also deserves more attention for the government and the public.

The Impact of Health Insurance on Healthcare Utilization by Migrant Workers in China.

Health insurance is an essential instrument to ensure equal access to medical resources and promote the health of the general population. Robust evidence regarding whether migrant workers have benefited from available insurance schemes is limited. Drawing on survey data from the Rural Urban Migration in China (RUMiC) Project, this paper examines the effects of health insurance on migrant workers' utilization of routine medical services, the medical burden, and the utilization of preventive medical services using a two-part model, the Heckman model, the Tobit model, and a probit model. Our findings indicate that, first, participating in medical insurance increases migrant workers' probability of visiting a doctor. Unlike other medical insurance programs that positively affect migrant workers' medical expenditure, the new rural cooperative medical system fails to play an effective role. Second, participation in any medical insurance program effectively reduces migrant workers' medical burden and can improve the probability of preventive medical service utilization. Third, self-reported health and disease severity are pivotal to determining migrant workers' medical expenditure. Fourth, high-income people have a good health status and a lower probability of becoming ill and can afford relatively higher medical expenses once they become ill. China's medical insurance appears to mainly serve to reduce the financial burden for serious illnesses, reflecting important policy implications for policy-makers.

Nitric oxide as a source for bacterial triazole biosynthesis.

The heterocycle 1,2,3-triazole is among the most versatile chemical scaffolds and has been widely used in diverse fields. However, how nature creates this nitrogen-rich ring system remains unknown. Here, we report the biosynthetic route to the triazole-bearing antimetabolite 8-azaguanine. We reveal that its triazole moiety can be assembled through an enzymatic and non-enzymatic cascade, in which nitric oxide is used as a building block. These results expand our knowledge of the physiological role of nitric oxide synthase in building natural products with a nitrogen-nitrogen bond, and should also inspire the development of synthetic biology approaches for triazole production.