Regarding the importance of N-degron pathway in protein degradation network, the adaptor protein ClpS recognizes the substrates bearing classical N-degrons, and delivers them to caseinolytic protease complex ClpAP for degradation. Interestingly, the majority of N-degrons located near the N-terminus of protein substrate are belonged to the hydrophobic type amino acids. Chloroplast, an important organelle for plant photosynthesis, contain a diversified Clp degradation system. Despite several studies have confirmed that chloroplastic ClpS is able to interact with classical N-degrons derived from prokaryotes, whereas, the molecular mechanism underlying how the chloroplastic ClpS protein could recognize the substrate tagged by N-degrons is still unclear until now. Chlamydomonas reinhardtii is a kind of unicellular model organism for photosynthesis researches, which possesses a large cup-shaped chloroplast, and the corresponding genome data indicates that it owns bacterial homologous adaptor protein, named CrClpS1. However, the relevant biochemical knowledges, and protein structure researches for CrClpS1 adaptor aren't reported up to date. The molecular interactions between CrClpS1 and possible N-degrons are undefined as well. Here, we build a reliable homology model of CrClpS1 and find a hydrophobic pocket for N-degron binding. We combine molecular docking, molecular dynamic simulations, and MM/PBSA, MM/GBSA binding free energy estimations to elucidate the molecular properties of CrClpS1-N-degron interactions. Besides, we investigate the conformational changes for CrClpS1-apo in water-solvent environment and analyze its possible biological significances through a long time molecular dynamic simulation. Specifically, the adaptor CrClpS1 displays the stronger interactions with Phe, Trp, Tyr, His and Ile with respect to other amino acids. Using the residue decomposition analysis, the interactions between CrClpS1 and N-degrons are heavily depended on several conservative residues, which are located around the hydrophobic pocket, implying that chloroplast isolated from Chlamydomonas reinhadtii adopts a relatively conservative N-degron recognition mode. Besides, the opening-closure of hydrophobic pocket of CrClpS1 might be beneficial for the N-degron selectivity.

In this paper,based on the existing models,an extended SEAIV model is established considering the influence of asymptomatic infected persons,the spread of free viruses,spatial diffusion,and other factors.On the premise of studying the existence of the positive solution of the model and giving the basic regeneration number R 0 as the threshold,the extinction and persistence of the disease are discussed,The stability of the disease-free equilibrium point of the model when R 0 ＜1 and the stability of the endemic equilibrium point when R 0 ＞ 1 is obtained.At the same time,the numerical simulation is used to verify the stability.The global attractivity of the disease-free equilibrium point of the model when R 0 =1 is further discussed.

The “Father of Hybrid Rice”, Yuan Longping, created high-yield hybrid rice that can feed tens of millions of people annually. The research achievements of Yuan and his team on low cadmium-accumulating rice and sea rice, in addition to hybrid rice, as well as those of a large number of Chinese scientists engaged in rice research in other six areas, including the rice genome, purple endosperm rice, de novo domestication of tetraploid rice, perennial rice, rice blast disease, and key genes for high nitrogen use efficiency, play an important role in promoting the realization of the United Nations Sustainable Development Goals 2 and 12. The purpose of this review is not to elaborate on the details of each research, but to innovatively summarize the significance and inspiration of these achievements to ensure global food security and achieve sustainable agriculture. In the future, cultivating new rice varieties through modern biotechnology, such as genome editing, will not only reduce hunger, but potentially reduce human-land conflicts, improve the environment, and mitigate climate change.

Alexander von Humboldt, was a great German geobotanist, educator and naturalist who greatly influenced science and humanities for more than two hundred years. In addition to scientific contributions (such as the understanding of vegetation distribution, the concepts of isotherm and pressure contours, and the initial concept of continental drift theory), he firmly believed in the concept of the interconnection of everything and the methodological approach of a holistic perspective to development, which has significance in achieving the UN Sustainable Development Goals, because they include both synergy and trade-offs among these goals. China has undergone tremendous changes since its reform and opening up in 1978 and now faces severe challenges in sustainable development. The scientific methods applied by Chinese scientists in sustainability fulfil the Humboldtian holistic perspective of nature. Here I provide four successful cases and their significant implications for addressing the increasingly severe water shortage, biological conservation, and conflicts between human well-being and land. The four examples discussed in this article are enlightened to establish a strong, just, and influential government and require empirical research to implement sustainable development plans. I believe that it's vital to encourage and supervise public participation for a successful program; for example, the participants should not be restricted to project executors, i.e., farmers or workers, but also students and scientists. Eradicating poverty must be prioritized, and well-being is the ultimate goal for sustainable development. This review article provides an extremely valuable reference for other developing or even developed countries to address sustainability challenges.

Tetracentron sinense is a deep-rooted, heliophilous, deciduous tree belonging to the Trochodendraceae family. T. sinense trees are beautifully shaped and are mainly distributed in the temperate and subtropical regions of East Asia. The tendency of T. sinense trees to grow on inaccessible, high-altitude hillsides (at 1100 m above sea level) may indicate that its populations were subjected to intensive human interference. Over the past 150 years, botanists have disputed the presence of xylem vessels in T. sinense. The newly released and resequenced genomes of T. sinense provide new perspectives on vessel evolution and the causes underling endangerment of species. Using cutting-edge sequencing technology, researchers obtained the total length of the chromosomes of 92.24% (1.07 Gb) of the 1.17 Gb assembled genome, with de novo assembly yielding 3389 contigs, with a contig N50 length of 1.99 Mb. Two whole-genome duplications (WGD) occurred and T. sinense diverged from the other tree species (Trochodendron aralioides) within the same family, 31 million years ago (Mya). The second WGD occurred at approximately 59–54 Mya, which may imply that it underwent evolutionary radiation during the Paleocene–Eocene Thermal Maximum, which is consistent with the genome evolution of many other dicotyledonous plants. Vascular-related NAC-domain 7 (VND7)-related genes, such as the NST/SMB subfamily, were found in its genome. These genes belong to the VNS gene family and are thought to be the master regulators of vessel differentiation; thus, they provide genetic evidence for vessel development. The resequenced genome data of T. sinense shows that two obvious genetic bottlenecks occurred during the ice age, which suggests a susceptibility of the species to climate change and may represent a genetic factor that led to the endangerment of the species.

The gradual transition of the algal ancestor from the freshwater to land has always attracted evolutionary biologists. The recent report of high-quality reference genomes of five Charophyta algae (Spirogloea muscicola, Mesotaenium endlicherianum, Mesostigma viride, Chlorokybus atmophyticus and Penium margaritaceum) and one hornwort (Anthoceros angustus) species sheds light on this fascinating transition. These early diverging plants and algae could have gained new genes from soil bacteria and fungi through horizontal gene transfer (HGT), which was so common during plant terrestrialization and may outrun our expectations. Through reviewing and critical thinking about the advancements on these plant genomes, here, I propose three prospective research directions that need to address in the future: (i) due to the ubiquitous nature of viruses that is similar to soil bacteria and fungi, there is less attention to viruses that probably also play an important role in the genome evolution of plants via HGT; (ii) multicellularity has occurred many times independently, but we still know a little about the biological and ecological mechanisms leading to multi-cellularity in Streptophyta; (iii) and most importantly, the quantitative relationships between genetic innovations and environmental variables such as temperature, precipitation and solar radiation, need pioneering research collaborated by biological evolutionists, computer scientists, and ecologists, which are crucial for understanding the macroevolution of plants and could also be used to simulate the evolution of plants under future climate change.

Switchgrass (Panicum virgatum L.) is a promising biofuel crop and one of the dominant species in North American tallgrass prairies. It grows rapidly, reaching up to 2.7 m, and planted fields remain productive for 15 years. The large, highly repetitive, and highly heterozygous genome of the generally tetraploid species have always been challenging for sequencing and assembly. Using PacBio long-read sequencing and bacterial artificial chromosome clone technology, researchers recently published a highly continuous genome assembly (v5) of a lowland switchgrass genotype AP13, which consisted of 626 contigs with a contig N50 of 5.5 Mb and a total of 97.2% bases that were assembled in the chromosomes. The AP13 switchgrass is allopolyploid and has a large genome (haploid genome size = 1129.9 Mb, with 56.9% repeats). Phylogenomic analysis suggested that the common ancestor of the two diploid genomes, N and K, in switchgrass diverged from the diploid sister Panicum hallii 8.352 million years ago (Mya). The N and K subgenomes themselves diverged 6.69 Mya and came together in the allopolyploid through whole-genome duplication (WGD) at approximately 4.6 Mya. Thus, the species arose during the Pliocene or early Pleistocene when cooling may have led to grasslands replacing forests. Resequencing of 732 switchgrass genotypes from ten common gardens spanning 1862 km identified three ecotypes: lowland, coastal, and highland ecotypes. Mean annual temperature and extreme 30-year minimum temperatures were observed to be highly correlated with biomass variation and winter mortality. During the expansion of northern upland habitats, the southern lowland ecotypes introduced the alleles from the preadapted northern gene pool through gene flow to accelerate their adaptation to harsh climates. The released high-quality genome, the identification of gene loci for biomass accumulation, and the quantification of climate–gene–biomass associations are crucial for de novo domestication via genome editing in the future.

研究了一类具有Michaelis-Menten收获率和时滞的微分代数生态经济模型的稳定性和Hopf分支问题.基于分支理论和稳定性理论,以时滞为分支参数,分析了系统在正平衡点处的特征方程,得到了正平衡点局部稳定的条件,进而得到Hopf分支产生的相关稳定性判据和条件,并进行数值模拟以说明分析结果.

Background In the past several millenniums, we have domesticated several crop species that are crucial for human civilization, which is a symbol of significant human influence on plant evolution. A pressing question to address is if plant diversity will increase or decrease in this warming world since contradictory pieces of evidence exit of accelerating plant speciation and plant extinction in the Anthropocene. Results Comparison may be made of the Anthropocene with the past geological times characterised by a warming climate, e.g., the Palaeocene-Eocene Thermal Maximum (PETM) 55.8 million years ago (Mya)-a period of "crocodiles in the Arctic", during which plants saw accelerated speciation through autopolyploid speciation. Three accelerators of plant speciation were reasonably identified in the Anthropocene, including cities, polar regions and botanical gardens where new plant species might be accelerating formed through autopolyploid speciation and hybridization. Conclusions However, this kind of positive effect of climate warming on new plant species formation would be thoroughly offset by direct and indirect intensive human exploitation and human disturbances that cause habitat loss, deforestation, land use change, climate change, and pollution, thus leading to higher extinction risk than speciation in the Anthropocene. At last, four research directions are proposed to deepen our understanding of how plant traits affect speciation and extinction, why we need to make good use of polar regions to study the mechanisms of dispersion and invasion, how to maximize the conservation of plant genetics, species, and diverse landscapes and ecosystems and a holistic perspective on plant speciation and extinction is needed to integrate spatiotemporally.

Reproductive phenology is sensitive to climatic changes and is associated with species functional types, distribution ranges, and their corresponding climatic niches. Phylogenetic niche conservatism in reproductive phenology also constrains its diversity and the distribution of species. Therefore, we assessed the effects of photosynthetic pathway, life history, phylogeny, and climatic niche on reproductive phenology. For 190 Poaceae species in subtropical China, we compiled data on flowering onset and reproductive period, functional type (photosynthetic pathway and life history), and 18 climatic variables across the species’ global distributions and used phylogenetic models to determine associations. We found strong phylogenetic signals in flowering onset but not in reproductive period. Photosynthetic pathway and life history have significant interactive effects on both flowering onset and reproductive period, such that C3 annual grasses flowered the earliest and had the longest reproductive period. We found that species with wider climatic niches would flower earlier and have longer reproductive periods. Specifically, species that experience wider ranges of mean annual precipitation and coldest-month temperatures would flower earlier, and species with higher mean annual temperature and wider ranges of wettest-quarter precipitation have a longer reproductive period. This study finds that the diversity of reproductive phenology among subtropical grasses is constrained by evolution and climatic niche and that photosynthetic pathway and life history have an interactive effect on the timing and the duration of reproduction.

Like many other ecosystems, subtropical forests are suffering more intense and longer droughts with the ongoing climate change. This study aimed to explore the seasonal transpiration and physiological responses of two dominant tree species,Schima superbaandMichelia macclurei, to manipulated precipitation patterns in a subtropical evergreen forest of South China, in which an ambient control treatment (BC), a drier dry and wetter wet season treatment (DD) and an extended dry and wetter wet season treatment (ED) were applied. Tree water use and associated ecophysiological characters, such as the daily whole-tree transpiration (E-L), intrinsic water use efficiency (WUEi), Huber values (A(s):A(l)) and utilization proportions from different water sources were determined during the period from October 2012 to September 2013. For both tree species, no significant difference in transpiration among the three treatments was observed in the wet season, and a relatively stronger decrease of transpiration occurred under DD and ED treatments during the later dry season. Moreover, the higher transpiration ofM. macclureiand its advantage of utilizing the shallow water derived from light rainfall under dry condition suggested that it has more survival and growth advantages in this subtropical forest. Therefore, under the seasonal drought caused by uneven distribution of rainfall in the future,M. macclureithat inclines to use shallow soil water would adopt a drought-avoidance strategy, whereasS. superbathat could uptake deeper soil water would be drought tolerant. The different spatial and temporal patterns of water use, together with the contrasting water use strategies, could reduce competition of the two species and facilitate their coexistence under potential precipitation distribution changes.

Transpiration through stomata in tree canopies plays an important role in terrestrial water cycles. However, the empirical relationship between leaf stomata anatomy and canopy stomatal conductance (G(s)) is surprisingly rare, thereby the underlying biological mechanisms of terrestrial water flux are not well elucidated. To gain further insight into these mechanisms, we reanalyzed the dataset of G(s) previously reported by Gao et al. (2015) using a quantile regression model. The results indicated that the reference G(s) (G(sref), G(s) at 1 kPa) was negatively correlated with wood density at each quantile, which confirmed previous data; however, G(sref) was significantly correlated with stomatal density at the 0.6 quantile, i.e., 450 stomata mm(-2). This highlighted the potential of using stomatal density as a trait to predict canopy water flux. A conceptual model of co-determinants of xylem and stomatal morphology suggests that these traits and their coordination may play a critical role in determining tree growth, physiological homeostatic response to environmental variables, water use efficiency, and drought resistance. Copyright (C) 2019 Kunming Institute of Botany, Chinese Academy of Sciences. Publishing services by Elsevier B.V.

As the big data accumulation in ecology picks up pace, we now have the opportunity to test several macroecological hypotheses, such as the latitudinal herbivory hypothesis (LHH) dated from the 1990s. The LHH proposes that plant-herbivore interactions decrease as latitude increases, that is, from lower latitudinal areas (i.e., the equator) to higher latitudinal areas (i.e., the poles). This hypothesis has been challenged in recent years. In this study, we used the greatest volume dataset of leaf herbivory from the study of Zhang et al. (Journal of Ecology, 104, 2016, 1089) to test the LHH at a global scale, based on a quantile regression model. We found that the mean annual temperature, mean annual precipitation, and potential net primary production were heterogeneously correlated with herbivory at different quantiles or variable intervals. Although the Northern Hemisphere (NH) and the global-scale trends are in accordance with the expected latitudinal variation, the Southern Hemisphere (SH) was found to exhibit inverse trends. The latitude has a negative effect on plant-herbivore interactions in the NH and on a global scale; leaf herbivory decreased more at a given latitude in higher latitudinal areas, which is attributed to harsher survival conditions in these areas. The uniformity of leaf herbivory variability along the climate and latitude gradient in the NH and on a global scale motivates that the loosening of this herbivory variability in the SH is not significant enough to dismiss the prevalence of the LHH, a testable macroecology hypothesis.

Reviewer 1 General comments: In this manuscript, Ouyang et al. present the results of a precipitation manipulation experiment in which the dry season was exacerbated or lengthened (along with a compensating increase in wet season water supply). The authors report a number of traits for the two dominant tree species at their experimental site, along with species-specific transpiration and water-use patterns. They conclude that the two dominant species show contrasting water-use strategies and their findings have important implications for the survival of these species under a changing climate C1

研究了具有时滞的分数阶模糊细胞神经网络,应用不等式与Banach不动点定理得到了系统解的存在唯一性条件和一致稳定性结果.最后,通过例子验证了定理的有效性.

This article comments on: Donald A. Levin. 2019. Plant speciation in the age of climate change. Annals of Botany 124(5): 769–775.

The ‘home-field advantage (HFA) hypothesis’ predicts a litter-field affinity effect on litter decomposition. In terrestrial ecosystems, plant roots have comprehensive roles in regulating litter-decomposer interactions, yet their potential influences on HFA remain unsolved. To fill this gap, we conducted a litter transplant experiment in a subtropical forest, and tested whether roots affect litter-field affinity via interactions with soil microbial functions.

Although several studies on the night-time water use of different plant species have been reported, comparative studies under the same climatic conditions of a region are scarce. This study aimed to analyse the inter- and intraspecific variations in night-time water use in relation to environmental factors and to tree morphological features to understand and elucidate the possible underlying mechanisms. The sap flow of three co-occurring tree species in a low subtropical secondary broadleaf forest in South China was monitored using Granier-style sap flux sensors. All examined environmental factors except wind speed exerted significant influence on the daytime sap flows of Schima superba, Castanopsis hystrix and Michelia macclurei, but the impacts of all factors, including wind speed, on the night-time sap flux were trivial. These results indicated that sap flow was mainly used for water recharge at night. The morphological features of the trees, except tree height, significantly affected the daytime water use, but no morphological features significantly affected the night-time water use. We found that night-time water recharge was strongly affected by the maximum flux density. A principal component analysis showed that there were more intraspecific than interspecific variations in water transport. The results also revealed that the night-time water use and the percentage of night/day (Qn/Qd) of photosynthetic stem species (C. hystrix and M. macclurei) were greater than those of non-photosynthetic stem species (S. superba).

An increasing body of evidence has shown that nighttime sap flux occurs in most plants, but the physiological implications and regulatory mechanism are poorly known. The significance of corticular photosynthesis has received much attention during the last decade, however, the knowledge of the relationship between corticular photosynthesis and nocturnal stem sap flow is limited at present. In this study, we divided seven tree species into two groups according to different photosynthetic capabilities: trees of species with (Castanopsis hystrix, Michelia macclurei, Eucalyptus citriodora, and Eucalyptus grandis × urophylla) and without (Castanopsis fissa, Schima superba, and Acacia auriculiformis) photosynthetic stems, and the sap flux (Js) and chlorophyll fluorescence parameters for these species were measured. One-way ANOVA analysis showed that the Fv/Fm (Maximum photochemical quantum yield of PSII) and ΦPSII (effective photochemical quantum yield of PSII) values were lower in non-photosynthetic stem species compared to photosynthetic stem species. The linear regression analysis showed that Js,d (daytime sap flux) and Js,n (nighttime sap flux) of non-photosynthetic stem species was 87.7 and 60.9% of the stem photosynthetic species. Furthermore, for a given daytime transpiration water loss, total nighttime sap flux was higher in species with photosynthetic stems (SlopeSMA = 2.680) than in non-photosynthetic stems species (SlopeSMA = 1.943). These results mean that stem corticular photosynthesis has a possible effect on the nighttime water flow, highlighting the important eco-physiological relationship between nighttime sap flux and corticular photosynthesis.