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101.
It is becoming more apparent that species richness alone many not be sufficient to fully understand ecosystem resilience but
that functional diversity (diversity of species having similar effects on an ecosystem process) may be more relevant. In particular,
response diversity (diversity of species that respond differently to disturbance) within functional groups (FG) is suggested
to be critical for resilience. We assess for the first time the use of response diversity as a measure of resilience in an
empirical study. Our experimental design consisted of sites with three disturbance intensities during a grazing exclosure
period and the same sites, 1 year later, after grazing. Plant FGs were identified based on effect traits related to nutrient
cycling and soil retention, and species richness within groups was assessed during exclosure and after grazing. To assess
if response diversity could predict loss of species richness (resilience analysis), response diversity was calculated only
during the exclosure period, based on traits related to grazing tolerance. We also assessed the contribution of richness to
response diversity during exclosure (redundancy analysis). Response diversity was significantly and highly correlated with
species richness within FGs during disturbance. That is, FGs with the lowest response diversity were the most affected, disappearing
when disturbance appeared. Richness within FGs during exclosure was not significantly correlated with response diversity,
showing that higher richness does not ensure resilience. We conclude that response diversity can be used to predict which
FGs are more resilient, and hence, less vulnerable to future disturbance. 相似文献
102.
A global experiment suggests climate warming will not accelerate litter decomposition in streams but might reduce carbon sequestration 总被引:2,自引:0,他引:2
Boyero L Pearson RG Gessner MO Barmuta LA Ferreira V Graça MA Dudgeon D Boulton AJ Callisto M Chauvet E Helson JE Bruder A Albariño RJ Yule CM Arunachalam M Davies JN Figueroa R Flecker AS Ramírez A Death RG Iwata T Mathooko JM Mathuriau C Gonçalves JF Moretti MS Jinggut T Lamothe S M'Erimba C Ratnarajah L Schindler MH Castela J Buria LM Cornejo A Villanueva VD West DC 《Ecology letters》2011,14(3):289-294
The decomposition of plant litter is one of the most important ecosystem processes in the biosphere and is particularly sensitive to climate warming. Aquatic ecosystems are well suited to studying warming effects on decomposition because the otherwise confounding influence of moisture is constant. By using a latitudinal temperature gradient in an unprecedented global experiment in streams, we found that climate warming will likely hasten microbial litter decomposition and produce an equivalent decline in detritivore-mediated decomposition rates. As a result, overall decomposition rates should remain unchanged. Nevertheless, the process would be profoundly altered, because the shift in importance from detritivores to microbes in warm climates would likely increase CO(2) production and decrease the generation and sequestration of recalcitrant organic particles. In view of recent estimates showing that inland waters are a significant component of the global carbon cycle, this implies consequences for global biogeochemistry and a possible positive climate feedback. 相似文献
103.
Corina M. Fusari Verónica V. Lia Verónica Nishinakamasu Jeremías E. Zubrzycki Andrea F. Puebla Alberto E. Maligne H. Esteban Hopp Ruth A. Heinz Norma B. Paniego 《Molecular breeding : new strategies in plant improvement》2011,28(1):73-89
Single nucleotide polymorphisms (SNPs) and insertions/deletions (indels) are increasingly used for cultivar identification,
construction of genetic maps, genetic diversity assessment, association mapping and marker-assisted breeding. Although there
are several highly sensitive methods for the detection of polymorphisms, most of them are often beyond the budget of medium-throughput
academic laboratories or seed companies. Heteroduplex analysis by enzymatic cleavage (CEL1CH) or denaturing high-performance
liquid chromatography (dHPLC) has been successfully used to examine genetic variation in several plant and animal species.
In this work, we assess and compare the performance of both methods in sunflower by genotyping SNPs from a set of 24 selected
polymorphic candidate genes. The CEL1CH method allowed us to accurately detect allele differences in 10 out of 24 regions
using an in-house prepared CEL1 enzyme (celery single strand endonuclease 1, Apium graveolens L.). Similarly, a total of 11 regions were successfully optimized for dHPLC analysis. As a scaling-up approach, both strategies
were tested to genotype either 42 SNPs/indels in 22 sunflower accessions from the local germplasm bank or 33 SNPs/indels in
90 recombinant inbred lines (RILs) for genetic mapping purposes. Summarizing, a total of 601 genotypes were efficiently analyzed
either with CEL1CH (110) or dHPCL (491). In conclusion, CEL1CH and dHPLC proved to be robust, complementary methods, allowing
medium-scale laboratories to scale up the number of both SNPs and individuals to be included in genetic studies and targeted
germplasm diversity characterization (EcoTILLING). 相似文献
104.
A Plonquet S Bastuji-Garin F Tahmasebi C Brisacier K Ledudal JP Farcet E Paillaud 《Immunity & ageing : I & A》2011,8(1):1-7
Background
Nosocomial infections are extremely common in the elderly and may be related to ageing of the immune system. The Immune Risk Phenotype (IRP), which predicts shorter survival in elderly patients, has not been evaluated as a possible risk factor for nosocomial infection. Our aim was to assess the prevalence of nosocomial infections in elderly in-patients and to investigate potential relationships between nosocomial infections and the immunophenotype, including IRP parameters.Results
We included 252 consecutive in-patients aged 70 years or over (mean age, 85 ± 6.2 years), between 2006 and 2008. Among them, 97 experienced nosocomial infections, yielding a prevalence rate of 38.5% (95% confidence interval, 32.5-44.5). The main infection sites were the respiratory tract (21%) and urinary tract (17.1%) When we compared immunological parameters including cell counts determined by flow cytometry in the groups with and without nosocomial infections, we found that the group with nosocomial infections had significantly lower values for the CD4/CD8 ratio and naive CD8 and CD4 T-cell counts and higher counts of memory CD8 T-cells with a significant increase in CD28-negative CD8-T cells. Neither cytomegalovirus status (positive in 193/246 patients) nor presence of the IRP was associated with nosocomial infections. However, nosocomial pneumonia was significantly more common among IRP-positive patients than IRP-negative patients (17/60 versus 28/180; p = 0.036).Conclusion
Immunological parameters that are easy to determine in everyday practice and known to be associated with immune system ageing and shorter survival in the elderly are also associated with an elevated risk of nosocomial pneumonia in the relatively short term. 相似文献105.
Angeli CB Kimura L Auricchio MT Vicente JP Mattevi VS Zembrzuski VM Hutz MH Pereira AC Pereira TV Mingroni-Netto RC 《Obesity (Silver Spring, Md.)》2011,19(6):1244-1251
We investigated whether variants in major candidate genes for food intake and body weight regulation contribute to obesity-related traits under a multilocus perspective. We studied 375 Brazilian subjects from partially isolated African-derived populations (quilombos). Seven variants displaying conflicting results in previous reports and supposedly implicated in the susceptibility of obesity-related phenotypes were investigated: β2-adrenergic receptor (ADRB2) (Arg16Gly), insulin induced gene 2 (INSIG2) (rs7566605), leptin (LEP) (A19G), LEP receptor (LEPR) (Gln223Arg), perilipin (PLIN) (6209T > C), peroxisome proliferator-activated receptor-γ (PPARG) (Pro12Ala), and resistin (RETN) (-420 C > G). Regression models as well as generalized multifactor dimensionality reduction (GMDR) were employed to test the contribution of individual effects and higher-order interactions to BMI and waist-hip ratio (WHR) variation and risk of overweight/obesity. The best multilocus association signal identified in the quilombos was further examined in an independent sample of 334 Brazilian subjects of European ancestry. In quilombos, only the PPARG polymorphism displayed significant individual effects (WHR variation, P = 0.028). No association was observed either with the risk of overweight/obesity (BMI ≥ 25 kg/m2), risk of obesity alone (BMI ≥ 30 kg/m2) or BMI variation. However, GMDR analyses revealed an interaction between the LEPR and ADRB2 polymorphisms (P = 0.009) as well as a third-order effect involving the latter two variants plus INSIG2 (P = 0.034) with overweight/obesity. Assessment of the LEPR-ADRB2 interaction in the second sample indicated a marginally significant association (P = 0.0724), which was further verified to be limited to men (P = 0.0118). Together, our findings suggest evidence for a two-locus interaction between the LEPR Gln223Arg and ADRB2 Arg16Gly variants in the risk of overweight/obesity, and highlight further the importance of multilocus effects in the genetic component of obesity. 相似文献
106.
107.
Assembly of TbetaRI:TbetaRII:TGFbeta ternary complex in vitro with receptor extracellular domains is cooperative and isoform-dependent 总被引:4,自引:0,他引:4
Zúñiga JE Groppe JC Cui Y Hinck CS Contreras-Shannon V Pakhomova ON Yang J Tang Y Mendoza V López-Casillas F Sun L Hinck AP 《Journal of molecular biology》2005,354(5):1052-1068
Transforming growth factor-beta (TGFbeta) isoforms initiate signaling by assembling a heterotetrameric complex of paired type I (TbetaRI) and type II (TbetaRII) receptors on the cell surface. Because two of the ligand isoforms (TGFbetas 1, 3) must first bind TbetaRII to recruit TbetaRI into the complex, and a third (TGFbeta2) requires a co-receptor, assembly is known to be sequential, cooperative and isoform-dependent. However the source of the cooperativity leading to recruitment of TbetaRI and the universality of the assembly mechanism with respect to isoforms remain unclear. Here, we show that the extracellular domain of TbetaRI (TbetaRI-ED) binds in vitro with high affinity to complexes of the extracellular domain of TbetaRII (TbetaRII-ED) and TGFbetas 1 or 3, but not to either ligand or receptor alone. Thus, recruitment of TbetaRI requires combined interactions with TbetaRII-ED and ligand, but not membrane attachment of the receptors. Cell-based assays show that TbetaRI-ED, like TbetaRII-ED, acts as an antagonist of TGFbeta signaling, indicating that receptor-receptor interaction is sufficient to compete against endogenous, membrane-localized receptors. On the other hand, neither TbetaRII-ED, nor TbetaRII-ED and TbetaRI-ED combined, form a complex with TGFbeta2, showing that receptor-receptor interaction is insufficient to compensate for weak ligand-receptor interaction. However, TbetaRII-ED does bind with high affinity to TGFbeta2-TM, a TGFbeta2 variant substituted at three positions to mimic TGFbetas 1 and 3 at the TbetaRII binding interface. This proves both necessary and sufficient for recruitment of TbetaRI-ED, suggesting that the three different TGFbeta isoforms induce assembly of the heterotetrameric receptor complex in the same general manner. 相似文献
108.
A comprehensive analysis of the NADP-malic enzyme gene family of Arabidopsis 总被引:8,自引:0,他引:8
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Wheeler MC Tronconi MA Drincovich MF Andreo CS Flügge UI Maurino VG 《Plant physiology》2005,139(1):39-51
The Arabidopsis (Arabidopsis thaliana) genome contains four genes encoding putative NADP-malic enzymes (MEs; AtNADP-ME1-ME4). NADP-ME4 is localized to plastids, whereas the other three isoforms do not possess any predicted organellar targeting sequence and are therefore expected to be cytosolic. The plant NADP-MEs can be classified into four groups: groups I and II comprising cytosolic and plastidic isoforms from dicots, respectively; group III containing isoforms from monocots; and group IV composed of both monocots and dicots, including AtNADP-ME1. AtNADP-MEs contained all conserved motifs common to plant NADP-MEs and the recombinant isozymes showed different kinetic and structural properties. NADP-ME2 exhibits the highest specific activity, while NADP-ME3 and NADP-ME4 present the highest catalytic efficiency for NADP and malate, respectively. NADP-ME4 exists in equilibrium of active dimers and tetramers, while the cytosolic counterparts are present as hexamers or octamers. Characterization of T-DNA insertion mutant and promoter activity studies indicates that NADP-ME2 is responsible for the major part of NADP-ME activity in mature tissues of Arabidopsis. Whereas NADP-ME2 and -ME4 are constitutively expressed, the expression of NADP-ME1 and NADP-ME3 is restricted by both developmental and cell-specific signals. These isoforms may play specific roles at particular developmental stages of the plant rather than being involved in primary metabolism. 相似文献
109.
Groundwater samples (111) from six different boreholes located in two geographical areas were examined for the presence of legionellae over a 7-year period. The number of Legionella isolates detected was generally low. The colonization of the aquifers was not uniform, and the persistence of Legionella was independent of the hydraulic pumps and the plumbing system present in the borehole. A total of 374 isolates identified by fatty acid methyl ester analysis belonged to Legionella pneumophila, L. oakridgensis, L. sainthelensi, and L. londiniensis. In area 1, L. oakridgensis constituted the major population detected, exhibiting only one random amplified polymorphic DNA (RAPD)-PCR profile. L. sainthelensi strains were less frequently isolated and also displayed a single RAPD profile, while L. pneumophila was only sporadically detected. In contrast, L. pneumophila comprised the vast majority of the isolates in area 2 and exhibited six distinct RAPD patterns, indicating the presence of different genetic groups; three L. londiniensis RAPD types were also detected. Two of the L. pneumophila and one of the L. londiniensis RAPD types were persistent in this environment for at least 12 years. The genetic structure of L. pneumophila groundwater populations, inferred from rpoB and dotA gene sequences, was peculiar, since the majority of the isolates were allied in a discrete group different from the lineages containing most of the type and reference strains of the three subspecies of L. pneumophila. Furthermore, gene exchange events related to the dotA allele could be envisioned. 相似文献
110.
NADP-malic enzyme and Hsp70: co-purification of both proteins and modification of NADP-malic enzyme properties by association with Hsp70 总被引:1,自引:0,他引:1
Different preparations of antibodies against 62 kDa NADP-malic enzyme (NADP-ME) from purified maize leaves cross-react with a 72 kDa protein from diverse tissues in many species. A 72 kDa protein, suggested to be a non-photosynthetic NADP-ME, has been purified from several plant species. However, to date, a cDNA coding for this putative 72 kDa NADP-ME has not been isolated. The screening of maize and tobacco leaf expression libraries using antibodies against purified 62 kDa NADP-ME allowed the identification of a heat shock protein (Hsp70). In addition, tandem mass spectrometry (MS/MS) studies indicate that along with NADP-ME, a 72 kDa protein, identified as an Hsp70 and reacting with the antibodies, is also purified from maize roots. On the other hand, the screening of a maize root cDNA library revealed the existence of a cDNA that encodes a mature 66 kDa NADP-ME. These results suggest that the 72 kDa protein is not actually an NADP-ME but in fact an Hsp70, at least in maize and tobacco. Probably, NADP-ME-Hsp70 association, taking place at least when preparing crude extracts, can lead to a co-purification of the proteins and can thus explain the cross-reaction of the antibodies. In the present work, we analyse and discuss a probable interaction of NADP-ME with Hsp70. 相似文献