Small GTPases:Structure,biological function and its interaction with nanoparticles

Small GTPase is a kind of GTP-binding protein commonly found in eukaryotic cells.It plays an important role in cytoskeletal reorganization,cell polarity,cell cycle progression,gene expression and many other significant events in cells,such as the interaction with foreign particles.Therefore,it is of great scientific significance to understand the biological properties of small GTPases as well as the GTPase-nano interplay,since more and more nanomedicine are supposed to be used in biomedical field.However,there is no review in this aspect.This review summarizes the small GTPases in terms of the structure,biological function and its interaction with nanoparticles.We briefly introduced the various nanoparticles such as gold/silver nanoparticles,SWCNT,polymeric micelles and other nano delivery systems that interacted with different GTPases.These current nanoparticles exhibited different pharmacological effect modes and various target design concepts in the small GTPases study.This will help to elucidate the conclusion that the therapeutic strategy targeting small GTPases might be a new research direction.It is believed that the in-depth study on the functional mechanism of GTPases can provide insights for the design and study of nanomedicines.

青藏高原高寒草甸灌丛化对圆穗蓼昆虫植食作用的影响

灌丛化在青藏高原高寒草甸普遍存在,其发生的可能原因包括全球变暖、CO_(2)浓度增加、过度放牧和人类活动等。灌丛化对草地生态系统有正负两方面的影响,且该影响的方向和强度依赖于环境条件。虽然已有诸多研究探讨了灌丛化对草地生态系统的影响,但其对昆虫植食作用的影响格局和机制仍不清楚。本研究以青藏高原高寒草甸常见物种圆穗蓼(Polygonum macrophyllum)为研究对象,通过比较不同盖度(0、50%、100%)的金露梅(Potentilla fruticosa)灌丛下圆穗蓼的昆虫植食作用,探究了灌丛化对昆虫植食作用的影响,以及这种影响如何随气候和土壤条件变化而变化。结果表明:(1)圆穗蓼昆虫植食作用随灌丛盖度增加而增强;(2)灌丛化对圆穗蓼昆虫植食作用的影响在年均温低、土壤有效磷含量低、土壤碳含量和氮含量高的情况下更显著。本研究揭示了灌丛化对青藏高原高寒草甸生态系统中圆穗蓼昆虫植食作用的影响,并进一步揭示这种影响具有环境依赖性。这一结论为探究灌丛化对草地昆虫植食作用的影响提供了证据,对于认识和科学管理青藏高原灌丛化草地具有重要的现实意义。

Dispersal and recruitment limitation contribute differently to community assembly

Aims The neutral theory of biodiversity has been criticized for being fragile with even slight deviations from its basic assumption of equal fitness among species.In response to this criticism,Hubbell((2001)The Unified Neutral Theory of Biodiversity and Biogeography.Princeton,NJ:Princeton University Press)proposed that competitive exclusion can be infinitely delayed by dispersal and recruitment limitation,thus making species effectively neutral.But the theoretical foundation for this claim still remains unclear and controversial,and the effects of dispersal and recruitment limitation are often confounded,especially in field studies.This study aims to provide an affirmative theoretical answer to the question of whether dispersal limitation and recruitment limitation can separately or jointly overwhelm the effects of fitness differences among species and lead to neutral community dynamics.Methods Computer simulations were used to investigate the effects of dispersal and recruitment limitation on delaying competitive exclusion in a homogeneous habitat in a spatially explicit context.Important Findings We found that even a slight competitive asymmetry would require extremely strong dispersal and recruitment limitation for neutrality to emerge.Most importantly,when the effects of dispersal and recruitment limitation were set apart,it is found that recruitment limitation is more effective in delaying competitive exclusion,whereas dispersal limitation tends to have a stronger impact on the general shape of both species abundance distributions and species–area relationships.

Plant diversity promotes soil fungal pathogen richness under fertilization in an alpine meadow

Aims The effects of fertilization on fungal plant pathogens in agricultural soils have been studied extensively.However,we know little about how fertilization affects the relative abundance and richness of soil fungal plant pathogens in natural ecosystems,either through altering the soil properties or plant community composition.Methods Here,we used data from a 7-year nitrogen(N)addition experiment in an alpine meadow on the Qinghai-Tibetan Plateau to test how N addition affects the relative abundance and richness of soil fungal plant pathogens,as determined using Miseq sequencing of ITS1 gene biomarkers.We also evaluated the relative importance of changes in soil properties versus plant species diversity under N addition.Important Findings Using general linear model selection and a piecewise structural equation model,we found that N addition increased the relative abundance of soil fungal plant pathogens by significantly altering soil properties.However,higher host plant species richness led to higher soil fungal plant pathogen richness,even after excluding the effects of N addition.We conclude that the relative abundance and richness of soil fungal plant pathogens are regulated by different mechanisms in the alpine meadow.Continuous worldwide N inputs(through both fertilizer use and nitrogen deposition)not only cause species losses via altered plant species interactions,but also produce changes in soil properties that result in more abundant soil fungal plant pathogens.This increase in pathogen relative abundance may seriously threaten ecosystem health,thus interrupting important ecosystem functions and services.

Explaining variation in productivity requires intraspecific variability in plant height among communities

While recent studies have shown the importance of intraspecific trait variation in the processes of community assembly,we still know little about the contributions of intraspecific trait variability to ecosystem functions.Here,we conducted a functional group removal experiment in an alpine meadow in Qinghai-Tibetan Plateau over 4 years to investigate the relative importance of inter-and intraspecific variability in plant height for productivity.We split total variability in plant height within each of 75 manipulated communities into interspecific variability(TV_(inter))and intraspecific variability within a community(ITV_(within)).Community-weighted mean height among communities was decomposed into fixed community-weighted mean(CWM_(fixed))and intraspecific variability among communities(ITV_(among)).We constructed a series of generalized additive mixed models and piecewise structural equation modeling to determine how trait variability(i.e.TV_(inter),ITV_(within),CWM_(fixed) and ITV_(among))indirectly mediated the changes in productivity in response to functional group removal.Community productivity was not only affected directly by treatment manipulations,but also increased with both inter-and intraspecific variability(i.e.CWM_(fixed) and ITV_(among))in plant height indirectly.This suggests that both the‘selection effect’and a‘shade-avoidance syndrome’can incur higher CWM_(fixed) and ITV_(among),and may simultaneously operate to regulate productivity.Our findings provide new evidence that,besides interspecific variability,intraspecific trait variability in plant height also plays a role in maintaining net primary productivity.

Exogenous and endogenous determinants of spatial aggregation patterns in tibetan Plateau meadow vegetation

Aims We aim to quantify the relative importance of various endogenous and exogenous processes influencing the spatial distribution of the individuals of plant species at different temporal and spatial scales in a species-rich and high-cover meadow in the eastern tibetan Plateau.Methods We calculated green’s index of dispersion to infer the spatial dis-tribution patterns of 73 herbaceous species at two scales(0.25 and 1.0 m2).We constructed a series of generalized linear models to test the hypotheses that different species traits such as mean plant stem density,per capita dry biomass,maximum plant height and mean seed mass contribute to their spatial distribution.We used the first principal component of soil C,N and P to explain abundance vari-ation across quadrats and sub-plots.Important Findingsthe individuals of the species studied were highly spatially aggregated.at both spatial scales,biomass and stem density explained the most variation in aggregation,but there was no evidence for an effect of mean seed mass on aggregation intensity.the effects of soil carbon,nitrogen and phosphorus at different depths affected plant abundance mostly at the broader spatial scale.our results demonstrate that self-thinning and habitat heterogeneity all contribute to determine the spatial aggregation patterns of plant individuals in alpine meadow vegetation in the eastern tibetan Plateau.

Neutral theory in community ecology

One of the central goals of community ecology is to understand the forces that maintain species diversity within communities.The traditional niche-assembly theory asserts that species live together in a community only when they differ from one another in resource uses.But this theory has some difficulties in explaining the diversity often observed in specie-rich communities such as tropical forests.As an alternative to the niche theory,Hubbell and other ecologists introduced a neutral model.Hubbell argues that the number of species in a community is controlled by species extinction and immigration or speciation of new species.Assuming that all individuals of all species in a trophically similar com-munity are ecologically equivalent,Hubbell’s neutral theory predicts two important statistical distributions.One is the asymptotic log-series distribution for the metacommunities under point mutation speciation,and the other is the zero-sum multinomial distribution for both local communities under dispersal limitation and metacommunities under random fission speciation.Unlike the niche-assembly theory,the neutral theory takes similarity in species and individuals as a starting point for investigating species diversity.Based on the fundamental processes of birth,death,dispersal and spe-ciation,the neutral theory provided the first mechanistic explanation of species abundance distribution commonly observed in natural communities.Since the publication of the neutral theory,there has been much discussion about it,pro and con.In this paper,we summarize recent progress in the assumption,prediction and speciation mode of the neutral theory,including progress in the theory itself,tests about the assumption of the theory,prediction and speciation mode at the metacommunity level.We also suggest that the most important task in the future is to bridge the niche-assembly theory and the neutral theory,and to add species differences to the neutral theory and more stochasticity to the niche theory.