Human activities have shaped large-scale distributions of many species, driving both range contractions and expansions. Species differ naturally in range size, with small-range species concentrated ...in particular geographic areas and potentially deviating ecologically from widespread species. Hence, species’ responses to human activities may be influenced by their geographic range sizes, but if and how this happens are poorly understood. Here, we use a comprehensive distribution database and species distribution modeling to examine if and how human activities have affected the extent to which 9,701 vascular plants fill their climatic potential ranges in China. We find that narrow-ranged species have lower range filling and widespread species have higher range filling in the human-dominated southeastern part of China, compared with their counterparts distributed in the less human-influenced northwestern part. Variations in range filling across species and space are strongly associated with indicators of human activities (human population density, human footprint, and proportion of cropland) even after controlling for alternative drivers. Importantly, narrow-ranged and widespread species show negative and positive range-filling relationships to these human indicators, respectively. Our results illustrate that floras risk biotic homogenization as a consequence of anthropogenic activities, with narrow-ranged species becoming replaced by widespread species. Because narrow-ranged species are more numerous than widespread species in nature, negative impacts of human activities will be prevalent. Our findings highlight the importance of establishing more protected areas and zones of reduced human activities to safeguard the rich flora of China.
Sesquiterpene synthases (STPSs) catalyze carbocation‐driven cyclization reactions that can generate structurally diverse hydrocarbons. The deprotonation‐reprotonation process is widely used in STPSs ...to promote structural diversity, largely attributable to the distinct regio/stereoselective reprotonations. However, the molecular basis for reprotonation regioselectivity remains largely understudied. Herein, we analyzed two highly paralogous STPSs, Artabotrys hexapetalus (−)‐cyperene synthase (AhCS) and ishwarane synthase (AhIS), which catalyze reactions that are distinct from the regioselective protonation of germacrene A (GA), resulting in distinct skeletons of 5/5/6 tricyclic (−)‐cyperene and 6/6/5/3 tetracyclic ishwarane, respectively. Isotopic labeling experiments demonstrated that these protonations occur at C3 and C6 of GA in AhCS and AhIS, respectively. The cryo‐electron microscopy‐derived AhCS complex structure provided the structural basis for identifying different key active site residues that may govern their functional disparity. The structure‐guided mutagenesis of these residues resulted in successful functional interconversion between AhCS and AhIS, thus targeting the three active site residues L311‐S419‐C458/M311‐V419‐A458 that may act as a C3/C6 reprotonation switch for GA. These findings facilitate the rational design or directed evolution of STPSs with structurally diverse skeletons.
Three critical active site residues L311‐S419‐C458/M311‐V419‐A458 were identified as the switch of the regioselective C3/C6 reprotonation of germacrene A in sesquiterpene synthase catalysis through the characterization and engineering of two highly paralogous sesquiterpene synthases, AhCS and AhIS, using a combination of isotopic labeling experiments, cryo‐electron microscopy, and structure‐guided mutagenesis.
Microbial diversity is generally far higher than plant diversity, but the relationship between microbial diversity and plant diversity remains enigmatic. To shed light on this problem, we examined ...the diversity of a key guild of root‐associated microbes, that is, ectomycorrhizal (EM) fungi along a plant diversity gradient in a Chinese subtropical forest. The results indicated that EM fungal diversity was positively correlated with host plant diversity. Furthermore, this relationship was best predicted by host genus‐level diversity, rather than species‐level diversity or family‐level diversity. The generality of this finding was extended beyond our study system through the analyses of 100 additional studies of EM fungal communities from tropical and temperate forests. Here as well, EM fungal lineage composition was significantly affected by EM plant diversity levels, and some EM fungal lineages were co‐associated with some host plant genera. These results suggest a general diversity maintenance mechanism for host‐specific microbes based on higher order host plant phylogenetic diversity.
Elucidating interactions of above-ground and below-ground communities in different habitat types is essential for understanding biodiversity maintenance and ecosystem functioning.
Using 454 ...pyrosequencing of ITS2 sequences we examined the relationship between subtropical mountain forest soil fungal communities, abiotic conditions, and plant communities using correlation and partial models.
Ridge and valley habitats with differing fungal communities were delineated. Total, saprotrophic and pathogenic fungal richness were significantly correlated with plant species richness and/or soil nutrients and moisture in the ridge habitat, but with habitat convexity or basal area of Castanopsis eyrei in the valley habitat. Ectomycorrhizal (EM) fungal richness was significantly correlated with basal area of C. eyrei and total EM plants in the ridge and valley habitats, respectively. Total, saprotrophic, pathogenic and EM fungal compositions were significantly correlated with plant species composition and geographic distance in the ridge habitat, but with various combinations of plant species composition, plant species richness, soil C : N ratio and pH or no variables in the valley habitat.
Our findings suggest that mechanisms influencing soil fungal diversity and community composition differ between ridge and valley habitats, and relationships between fungal and woody plant assemblages depend on habitat types in the subtropical forest ecosystem.
Elucidating symbiotic relationships between arbuscular mycorrhizal fungi (AMF) and plants contributes to a better understanding of their reciprocally dependent coexistence and community assembly. ...However, the main drivers of plant and AMF community assembly remain unclear. In this study, we examined AMF communities from 166 root samples of 17 woody plant species from 10 quadrats in a Chinese subtropical forest using 454 pyrosequencing of 18S rRNA gene to describe symbiotic AMF–plant association. Our results show the woody plant–AMF networks to be highly interconnected and nested, but in antimodular and antispecialized manners. The nonrandom pattern in the woody plant–AMF network was explained by plant and AMF phylogenies, with a tendency for a stronger phylogenetic signal by plant than AMF phylogeny. This study suggests that the phylogenetic niche conservatism in woody plants and their AMF symbionts could contribute to interdependent AMF and plant community assembly in this subtropical forest ecosystem.
Global biodiversity decline and its cascading effects through trophic interactions pose a severe threat to human society. Establishing the impacts of biodiversity decline requires a more thorough ...understanding of multi‐trophic interactions and, more specifically, the effects that loss of diversity in primary producers has on multi‐trophic community assembly.
Within a synthetic conceptual framework for multi‐trophic beta‐diversity, we tested a series of hypotheses on neutral and niche‐based bottom‐up processes in assembling herbivore and carnivore communities in a subtropical forest using linear models, hieratical variance partitioning based on linear mixed‐effects models (LMMs) and simulation.
We found that the observed taxonomic, phylogenetic and functional beta‐diversity of both herbivorous caterpillars and carnivorous spiders were significantly and positively related to tree dissimilarity. Linear models and variance partitioning for LMMs jointly suggested that as a result of bottom‐up effects, producer dissimilarities were predominant in structuring consumer dissimilarity, the strength of which highly depended on the trophic dependencies on producers, the diversity facet examined, and data quality. Importantly, linear models for standardized beta‐diversities against producer dissimilarities implied a transition between niche‐based processes such as environmental filtering and competitive exclusion, which supports the role of bottom‐up effect in determining consumer community assembly.
These findings enrich our mechanistic understanding of the ‘Diversity Begets Diversity’ hypothesis and the complexity of higher‐trophic community assembly, which is fundamental for sustainable biodiversity conservation and ecosystem management.
概括
全球范围内生物多样性下降正对全球生态系统功能构成威胁。而特定类群的生物多样性下降又会通过营养级关系(例如，bottom‐up effect上行效应和top‐down effect下行效应)对不同营养级类群的生物多样性和整个生态系统产生复杂影响。在此背景下，揭示不同营养级之间生物多样性变化的关联机制对于理解多营养级组成的群落构建和生物多样性的维持机制至关重要。在多营养级群落构建机制的研究中，最为经典的“Diversity begets diversity”理论常常用于解释不同营养级alpha多样性的关联机制研究，而对于营养级之间多维度beta多样性的关联机制研究相对较少。
本研究依托中国亚热带生物多样性与生态系统功能 (BEF‐China，江西德兴) 野外实验样地，对植物、植食性无脊椎动物(鳞翅目幼虫)和捕食性无脊椎动物(蜘蛛)的物种组成、功能特征数据进行了系统调查，并构建不同类群物种的种间系统发育关系。根据生态位理论和中性理论的预测，本研究分别在beta多样性观测值空间格局、beta多样性观测值变异解释和beta多样性标准值空间格局三个维度提出假设，系统评估了亚热带森林中植物组成(代表生态位过程中的上行效应)和空间距离(代表中性扩散过程)对这两个营养级群落构建的相对重要性。
研究表明，植食性和捕食性无脊椎动物的物种、谱系和功能beta多样性均与植物beta多样性存在显著正相关关系。基于线性混合模型的方差分解结果表明，植物组成的变化通过上行效应决定了植食性和捕食性无脊椎动物的群落组成结构，并且该影响同时受到营养级关系强度、多样性维度和数据质量(0‐1数据/基于多度的数据)的影响。此外，基于零模型分析的beta多样性标准值空间格局也证实了生态位过程在植食性和捕食性无脊椎动物群落构建过程中的重要性。
综上所述，这些研究结果证实了植物beta多样性通过上行效应对其高营养级类群beta多样性的影响机制，进一步拓展了我们对亚热带森林中多营养级群落构建及生物多样性维持机制的理解。
This work enriches our mechanistic understanding of the ‘Diversity Begets Diversity’ hypothesis and the complexity of higher‐trophic community assembly, which is fundamental for sustainable biodiversity conservation and ecosystem management.
Schima superba is an important dominant species in subtropical evergreen broadleaved forests of China, and plays a vital role in community structure and dynamics. However, the survival rate of its ...seedlings in the field is low, and water shortage could be a factor that limits its regeneration. In order to better understand the response of its seedlings to drought stress on a functional genomics scale, RNA-seq technology was utilized in this study to perform a large-scale transcriptome sequencing of the S. superba seedlings under drought stress. More than 320 million clean reads were generated and 72218 unique transcripts were obtained through de novo assembly. These unigenes were further annotated by blasting with different public databases and a total of 53300 unique transcripts were annotated. A total of 31586 simple sequence repeat (SSR) loci were presented. Through gene expression profiling analysis between drought treatment and control, 11038 genes were found to be significantly enriched in drought-stressed seedlings. Based on these differentially expressed genes (DEGs), Gene Ontology (GO) terms enrichment and Kyoto Encyclopedia of Genes and Genomes pathway (KEGG) enrichment analysis indicated that drought stress caused a number of changes in the types of sugars, enzymes, secondary mechanisms, and light responses, and induced some potential physical protection mechanisms. In addition, the expression patterns of 18 transcripts induced by drought, as determined by quantitative real-time PCR, were consistent with their transcript abundance changes, as identified by RNA-seq. This transcriptome study provides a rapid method for understanding the response of S. superba seedlings to drought stress and provides a number of gene sequences available for further functional genomics studies.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Epilepsy is considered to result from an imbalance between excitation and inhibition of the central nervous system. Pathogenic mutations in the methyl-CpG binding domain protein 5 gene (MBD5) are ...known to cause epilepsy. However, the function and mechanism of MBD5 in epilepsy remain elusive. Here, we found that MBD5 was mainly localized in the pyramidal cells and granular cells of mouse hippocampus, and its expression was increased in the brain tissues of mouse models of epilepsy. Exogenous overexpression of MBD5 inhibited the transcription of the signal transducer and activator of transcription 1 gene (Stat1), resulting in increased expression of N-methyl-d-aspartate receptor (NMDAR) subunit 1 (GluN1), 2A (GluN2A) and 2B (GluN2B), leading to aggravation of the epileptic behaviour phenotype in mice. The epileptic behavioural phenotype was alleviated by overexpression of STAT1 which reduced the expression of NMDARs, and by the NMDAR antagonist memantine. These results indicate that MBD5 accumulation affects seizures through STAT1-mediated inhibition of NMDAR expression in mice. Collectively, our findings suggest that the MBD5-STAT1-NMDAR pathway may be a new pathway that regulates the epileptic behavioural phenotype and may represent a new treatment target.
•MBD5 was mainly localized in the cytoplasm and nucleus of neurons.•Expression of MBD5 was increased in brain tissues of epileptic mouse models.•Increased MBD5 inhibited the transcription of Stat1, resulting in increased expression of NMDAR subunits and aggravation of epileptic behavioural phenotype in mice.•Upregulation of STAT1 expression or the use of the NMDAR antagonism alleviated this phenotype.•MBD5-STAT1-NMDAR pathway may be a new pathway that regulates the epileptic behavioural phenotype and may represent a new treatment target.
Habitat fragmentation and loss is the main cause of species extinction; thus, the appropriate placement of protected areas is critical for saving vulnerable and threatened species. However, how to ...expand the existing protected areas network for improving conservation efficiency is a vital concern. We examined the Qinling Mountains — a widely recognized biogeographic treasure in China and East Asia, to identify key biodiversity areas (KBAs) and compare them with existing protected areas. We focused on 259 key protected wild plant and animal species and modeled species distributions with elevation and habitat preference. We then adapted two established algorithms (biodiversity hotspots of species richness BHSR and systematic conservation planning SCP) to identify priority areas, respectively. Results from these two algorithms addressed two conservation criteria: “represented” single species and “well-represented” species assemblages. SCP showed better performance (~90%) than BHSR (~78%) using the “represented” criterion covering a small portion (~8%) of the total region; conversely, BHSR showed better performance (~61%) than SCP (~55%) using the “well-represented” criterion. The overlapping priority areas of both methods could achieve an optimal conservation that met dual criteria, which is considered as the candidate KBAs in this study. Surprisingly, we found that 63% of KBAs are not co-occurring with existing national nature reserves (NNRs). We highlight the unoccupied KBAs as deserving additional protection, with a result that the expansion of NNRs to KBAs will increase overall conservation coverage and efficiency. The integrated method developed here can be used generally as a repeatable and quantitative assessment framework to be implemented in protected areas network expansion and planning, in China and beyond.
•KBAs are identified by SCP and BHSR, respectively.•Represented and well-represented are used to assess the represented efficiencies.•Represented efficiencies of SCP and BHSR are compared.•63% of KBAs were still outside the NNRs.•This methodology can be repeated in other places.
Carbon fiber reinforced plastics (CFRP) have many mechanical properties that are superior to those of conventional structural materials and are becoming more and more widely used. Monitoring the ...curing process used to produce such composite material is important to ensure the quality of the process, especially for the characterization of residual strains after the material has been manufactured. In this study, we present a tilted fiber Bragg grating (TFBG) sensor used to monitor the curing of CFRP composite materials. The TFBG sensor was embedded into the layers of CFRP laminates to study the curing residual strain of the laminates. The experimental results showed that the curing residual stress was about −22.25 MPa, the axial residual strain was −281.351 με, and lateral residual strain of 89.91 με. The TFBG sensor was found to be sensitive to the curing residual strain of the CFRP, meaning that it has potential for use in applications involving composite curing processes. Moreover, it is indeed possible to improve the properties of composite materials via the optimization and monitoring of their curing parameters.
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