Improved redox homeostasis owing to the up-regulation of one-carbon metabolism and related pathways is crucial for yeast heterosis at high temperature.

Heterosis or hybrid vigor is a common phenomenon in plants and animals; however, the molecular mechanisms underlying heterosis remain elusive, despite extensive studies on the phenomenon for more than a century. Here we constructed a large collection of F1 hybrids of Saccharomyces cerevisiae by spore-to-spore mating between homozygous wild strains of the species with different genetic distances and compared growth performance of the F1 hybrids with their parents. We found that heterosis was prevalent in the F1 hybrids at 40°C. A hump-shaped relationship between heterosis and parental genetic distance was observed. We then analyzed transcriptomes of selected heterotic and depressed F1 hybrids and their parents growing at 40°C and found that genes associated with one-carbon metabolism and related pathways were generally up-regulated in the heterotic F1 hybrids, leading to improved cellular redox homeostasis at high temperature. Consistently, genes related with DNA repair, stress responses, and ion homeostasis were generally down-regulated in the heterotic F1 hybrids. Furthermore, genes associated with protein quality control systems were also generally down-regulated in the heterotic F1 hybrids, suggesting a lower level of protein turnover and thus higher energy use efficiency in these strains. In contrast, the depressed F1 hybrids, which were limited in number and mostly shared a common aneuploid parental strain, showed a largely opposite gene expression pattern to the heterotic F1 hybrids. We provide new insights into molecular mechanisms underlying heterosis and thermotolerance of yeast and new clues for a better understanding of the molecular basis of heterosis in plants and animals.

NHC-Activations on α-, ß-, γ-, and Beyond.

Over the recent decades, due to the special electronic characteristics and diverse reactivities, N-heterocyclic carbene (NHC) has received significant interest in organocatalyzed reactions. The formation of Breslow intermediates by NHC can convert into acyl anion equivalent, enolates, homoenolate, acyl azolium, and vinyl enolate etc., and the cycloaddition reactions of these species has attracted lots of attention. In this review, we focus on the summry of the development of NHC-activation of carbonyl carbon (or imine carbon) in situ, α-, ß-, γ-, and beyond, and the cycloaddition reaction of these species.

Highly diverged lineages of Saccharomyces paradoxus in temperate to subtropical climate zones in China.

The wild yeast Saccharomyces paradoxus has become a new model in ecology and evolutionary biology. Different lineages of S. paradoxus have been recognized across the world, but the distribution and genetic diversity of the species remain unknown in China, where the origin of its sibling species S. cerevisiae lies. In this study, we investigated the ecological and geographic distribution of S. paradoxus through an extensive field survey in China and performed population genomic analysis on a set of S. paradoxus strains, including 27 strains, representing different geographic and ecological origins within China, and 59 strains representing all the known lineages of the species recognized in the other regions of the world so far. We found two distinct lineages of S. paradoxus in China. The majority of the Chinese strains studied belong to the Far East lineage, and six strains belong to a novel highly diverged lineage. The distribution of these two lineages overlaps ecologically and geographically in temperate to subtropical climate zones in China. With the addition of the new China lineage, the Eurasian population of S. paradoxus exhibits higher genetic diversity than the American population. We observed more possible lineage-specific introgression events from the Eurasian lineages than from the American lineages. Our results expand the knowledge on ecology, genetic diversity, biogeography, and evolution of S. paradoxus.

Online rumors during the COVID-19 pandemic: co-evolution of themes and emotions.

Introduction: During public health emergencies, online rumors spread widely on social media, causing public information anxiety and emotional fluctuations. Analyzing the co-evolution patterns of online rumor themes and emotions is essential for implementing proactive and precise governance of online rumors during such events. Methods: Rumor texts from mainstream fact-checking platforms during the COVID-19 pandemic were collected and analyzed in phases based on the crisis lifecycle theory. The LDA topic model was applied to analyze the distribution of rumor themes at different stages. The Baidu AI Sentiment Analysis API was used to study the emotional tendencies of rumors at different stages. Line graphs were utilized to analyze the co-evolution characteristics of rumor themes and emotions. Results: During the COVID-19 pandemic, the themes of online rumors can be categorized into five types: epidemic prevention and control, panic-inducing, production and livelihood, virus dissemination, and social figures. These themes exhibited repetition and fluctuation at different stages of the pandemic. The emotions embedded in pandemic-related online rumors evolved with the progression of the pandemic. Panic-inducing rumors co-evolved with negative emotions, while epidemic prevention and control rumors co-evolved with positive emotions. Conclusion: The study results help to understand the public's focus and emotional tendencies at different stages of the COVID-19 pandemic, thereby enabling targeted public opinion guidance and crisis management.

An antibacterial biologic patch based on bacterial cellulose for repair of infected hernias.

Infection-associated complications and repair failures and antibiotic resistance have emerged as a formidable challenge in hernia repair surgery. Consequently, the development of antibiotic-free antibacterial patches for hernia repair has become an exigent clinical necessity. Herein, a GBC/Gel/LL37 biological patch (biopatch) with exceptional antibacterial properties is fabricated by grafting 2-Methacryloyloxyethyl trimethylammonium chloride (METAC), a unique quaternary ammonium salt with vinyl, onto bacterial cellulose (GBC), followed by compounding with gelatin (Gel) and LL37. The GBC/Gel/LL37 biopatch exhibits stable swelling capacity, remarkable mechanical properties, flexibility, and favorable biocompatibility. The synergistic effect of METAC and LL37 confers upon the GBC/Gel/LL37 biopatch excellent antibacterial efficacy against Staphylococcus aureus and Escherichia coli, effectively eliminating invading bacteria without the aid of exogenous antibiotics in vivo while significantly reducing local acute inflammation caused by infection. Furthermore, the practical efficacy of the GBC/Gel/LL37 biopatch is evaluated in an infected ventral hernia model, revealing that the GBC/Gel/LL37 biopatch can prevent the formation of visceral adhesions, facilitate the repair of infected ventral hernia, and effectively mitigate chronic inflammation. The prepared antibacterial GBC/Gel/LL37 biopatch is very effective in dealing with the risk of infection in hernia repair surgery and offers potential clinical opportunities for other soft injuries, exhibiting considerable clinical application prospects.

Cellulose hydrogel-based biodegradable and recyclable magnetoelectric composites for electromechanical conversion.

Flexible electromechanical conversion devices have attracted enormous attention as energy harvesters and self-powered sensors in the fields of wearable electronics and robotics. However, current flexible devices composed of plastic polymers and metals suffer from non-degradability and limited recyclability. Herein, a biodegradable and recyclable hydrogel-based magnetoelectric (ME) composite is fabricated via introducing NdFeB magnetic particles and copper wires into the regenerated bacterial cellulose (rBC) hydrogel. The developed hydrogel-based ME composites can effectively convert the mechanical kinetic energy into electrical energy based on the principle of electromagnetic induction, which maximum voltage reaches 15 µV. In addition, degradation experiments are conducted in this work to demonstrate the hydrogel can be rapidly degraded within 3 h under the condition of enzyme and completely natural degraded within 49 days in water, respectively. Moreover, the left NdFeB particles and copper wires can be recyclable and reused for the same devices, leaving no environmentally hazardous electronic waste.

Genetic diversity and population structure of the amylolytic yeast Saccharomycopsis fibuligera associated with Baijiu fermentation in China.

The amylolytic yeast Saccharomycopsis fibuligera is a predominant species in starters and the early fermentation stage of Chinese liquor (Baijiu). However, the genetic diversity of the species remains largely unknown. Here we sequenced the genomes of 97 S. fibuligera strains from different Chinese Baijiu companies. The genetic diversity and population structure of the strains were analyzed based on 1,133 orthologous genes and the whole genome single nucleotide polymorphisms (SNPs). Four main lineages were recognized. One lineage contains 60 Chinese strains which are exclusively homozygous with relatively small genome sizes (18.55-18.72 Mb) and low sequence diversity. The strains clustered in the other three lineages are heterozygous with larger genomes (21.85-23.72 Mb) and higher sequence diversity. The genomes of the homozygous strains showed nearly 100% coverage with the genome of the reference strain KPH12 and the sub-genome A of the hybrid strain KJJ81 at the above 98% sequence identity level. The genomes of the heterozygous strains showed nearly 80% coverage with both the sub-genome A and the whole genome of KJJ81, suggesting that the Chinese heterozygous strains are also hybrids with nearly 20% genomes from an unidentified source. Eighty-three genes were found to show significant copy number variation between different lineages. However, remarkable lineage specific variations in glucoamylase and α-amylase activities and growth profiles in different carbon sources and under different environmental conditions were not observed, though strains exhibiting relatively high glucoamylase activity were mainly found from the homozygous lineage.