排序方式: 共有53条查询结果,搜索用时 31 毫秒
21.
Phylogenetic analyses have identified the water lilies (Nymphaeales: Cabombaceae and Nymphaeaceae), together with four other small groups of flowering plants (the 'ANITA clades': Amborellaceae, Illiciales, Trimeniaceae, Austrobaileyaceae), as the first diverging lineages from the main branch of the angiosperm phylogenetic tree, but evidence of these groups in the earliest phases of the angiosperm fossil record has remained elusive. Here we report the earliest unequivocal evidence, based on fossil floral structures and associated pollen, of fossil plants related to members of the ANITA clades. This extends the history of the water lilies (Nymphaeales) back to the Early Cretaceous (125-115 million years) and into the oldest fossil assemblages that contain unequivocal angiosperm stamens and carpels. This discovery adds to the growing congruence between results from molecular-based analyses of relationships among angiosperms and the palaeobotanical record. It is also consistent with previous observations that the flowers of early angiosperms were generally very small compared with those of their living relatives. 相似文献
22.
Galactofuranose-containing glycoconjugates are present in numerous microbes, many of which are pathogenic for humans. Metabolic
aspects of the monosaccharide have proven difficult to elucidate, because galactofuranose metabolites and glycoconjugates
are relatively unstable during analyses. Recent advances in biochemical and genetic approaches, however, have facilitated
a better understanding of galactofuranose metabolism. This review summarizes our current information on its metabolism and
a few selected glycoconjugates containing this furanose.
RID="*"
ID="*"Corresponding author. 相似文献
23.
Multiple mating (polyandry) is widespread among animal groups, particularly insects. But the factors that maintain it and underlie its evolution are hard to verify because benefits and costs are not easily quantified and they tend to be similar in related species. Here we compare the mating strategies of the leaf-cutting ant Acromyrmex echinatior and its recently derived social parasite Acromyrmex insinuator, which is also its closest relative. We find that although the host queens mate with up to a dozen different males, the social parasite mates only singly. This rapid and surprising reversion to single mating in a socially parasitic ant indicates that the costs of polyandry are probably specific to a free-living lifestyle. 相似文献
24.
The nucleotide-binding proteins Nubp1 and Nubp2 are negative regulators of ciliogenesis 总被引:1,自引:1,他引:0
Elena Kypri Andri Christodoulou Giannis Maimaris Mette Lethan Maria Markaki Costas Lysandrou Carsten W. Lederer Nektarios Tavernarakis Stefan Geimer Lotte B. Pedersen Niovi Santama 《Cellular and molecular life sciences : CMLS》2014,71(3):517-538
Nucleotide-binding proteins Nubp1 and Nubp2 are MRP/MinD-type P-loop NTPases with sequence similarity to bacterial division site-determining proteins and are conserved, essential proteins throughout the Eukaryotes. They have been implicated, together with their interacting minus-end directed motor protein KIFC5A, in the regulation of centriole duplication in mammalian cells. Here we show that Nubp1 and Nubp2 are integral components of centrioles throughout the cell cycle, recruited independently of KIFC5A. We further demonstrate their localization at the basal body of the primary cilium in quiescent vertebrate cells or invertebrate sensory cilia, as well as in the motile cilia of mouse cells and in the flagella of Chlamydomonas. RNAi-mediated silencing of nubp-1 in C. elegans causes the formation of morphologically aberrant and additional cilia in sensory neurons. Correspondingly, downregulation of Nubp1 or Nubp2 in mouse quiescent NIH 3T3 cells markedly increases the number of ciliated cells, while knockdown of KIFC5A dramatically reduces ciliogenesis. Simultaneous double silencing of Nubp1 + KIFC5A restores the percentage of ciliated cells to control levels. We document the normal ciliary recruitment, during these silencing regimes, of basal body proteins critical for ciliogenesis, namely CP110, CEP290, cenexin, Chibby, AurA, Rab8, and BBS7. Interestingly, we uncover novel interactions of Nubp1 with several members of the CCT/TRiC molecular chaperone complex, which we find enriched at the basal body and recruited independently of the Nubps or KIFC5A. Our combined results for Nubp1, Nubp2, and KIFC5A and their striking effects on cilium formation suggest a central regulatory role for these proteins, likely involving CCT/TRiC chaperone activity, in ciliogenesis. 相似文献
25.
Many sequence variants affecting diversity of adult human height 总被引:1,自引:0,他引:1
Gudbjartsson DF Walters GB Thorleifsson G Stefansson H Halldorsson BV Zusmanovich P Sulem P Thorlacius S Gylfason A Steinberg S Helgadottir A Ingason A Steinthorsdottir V Olafsdottir EJ Olafsdottir GH Jonsson T Borch-Johnsen K Hansen T Andersen G Jorgensen T Pedersen O Aben KK Witjes JA Swinkels DW den Heijer M Franke B Verbeek AL Becker DM Yanek LR Becker LC Tryggvadottir L Rafnar T Gulcher J Kiemeney LA Kong A Thorsteinsdottir U Stefansson K 《Nature genetics》2008,40(5):609-615
Adult human height is one of the classical complex human traits. We searched for sequence variants that affect height by scanning the genomes of 25,174 Icelanders, 2,876 Dutch, 1,770 European Americans and 1,148 African Americans. We then combined these results with previously published results from the Diabetes Genetics Initiative on 3,024 Scandinavians and tested a selected subset of SNPs in 5,517 Danes. We identified 27 regions of the genome with one or more sequence variants showing significant association with height. The estimated effects per allele of these variants ranged between 0.3 and 0.6 cm and, taken together, they explain around 3.7% of the population variation in height. The genes neighboring the identified loci cluster in biological processes related to skeletal development and mitosis. Association to three previously reported loci are replicated in our analyses, and the strongest association was with SNPs in the ZBTB38 gene. 相似文献
26.
Benzinou M Creemers JW Choquet H Lobbens S Dina C Durand E Guerardel A Boutin P Jouret B Heude B Balkau B Tichet J Marre M Potoczna N Horber F Le Stunff C Czernichow S Sandbaek A Lauritzen T Borch-Johnsen K Andersen G Kiess W Körner A Kovacs P Jacobson P Carlsson LM Walley AJ Jørgensen T Hansen T Pedersen O Meyre D Froguel P 《Nature genetics》2008,40(8):943-945
Mutations in PCSK1 cause monogenic obesity. To assess the contribution of PCSK1 to polygenic obesity risk, we genotyped tag SNPs in a total of 13,659 individuals of European ancestry from eight independent case-control or family-based cohorts. The nonsynonymous variants rs6232, encoding N221D, and rs6234-rs6235, encoding the Q665E-S690T pair, were consistently associated with obesity in adults and children (P = 7.27 x 10(-8) and P = 2.31 x 10(-12), respectively). Functional analysis showed a significant impairment of the N221D-mutant PC1/3 protein catalytic activity. 相似文献
27.
Unoki H Takahashi A Kawaguchi T Hara K Horikoshi M Andersen G Ng DP Holmkvist J Borch-Johnsen K Jørgensen T Sandbaek A Lauritzen T Hansen T Nurbaya S Tsunoda T Kubo M Babazono T Hirose H Hayashi M Iwamoto Y Kashiwagi A Kaku K Kawamori R Tai ES Pedersen O Kamatani N Kadowaki T Kikkawa R Nakamura Y Maeda S 《Nature genetics》2008,40(9):1098-1102
We conducted a genome-wide association study using 207,097 SNP markers in Japanese individuals with type 2 diabetes and unrelated controls, and identified KCNQ1 (potassium voltage-gated channel, KQT-like subfamily, member 1) to be a strong candidate for conferring susceptibility to type 2 diabetes. We detected consistent association of a SNP in KCNQ1 (rs2283228) with the disease in several independent case-control studies (additive model P = 3.1 x 10(-12); OR = 1.26, 95% CI = 1.18-1.34). Several other SNPs in the same linkage disequilibrium (LD) block were strongly associated with type 2 diabetes (additive model: rs2237895, P = 7.3 x 10(-9); OR = 1.32, 95% CI = 1.20-1.45, rs2237897, P = 6.8 x 10(-13); OR = 1.41, 95% CI = 1.29-1.55). The association of these SNPs with type 2 diabetes was replicated in samples from Singaporean (additive model: rs2237895, P = 8.5 x 10(-3); OR = 1.14, rs2237897, P = 2.4 x 10(-4); OR = 1.22) and Danish populations (additive model: rs2237895, P = 3.7 x 10(-11); OR = 1.24, rs2237897, P = 1.2 x 10(-4); OR = 1.36). 相似文献
28.
Morth JP Pedersen BP Toustrup-Jensen MS Sørensen TL Petersen J Andersen JP Vilsen B Nissen P 《Nature》2007,450(7172):1043-1049
The Na+,K+-ATPase generates electrochemical gradients for sodium and potassium that are vital to animal cells, exchanging three sodium ions for two potassium ions across the plasma membrane during each cycle of ATP hydrolysis. Here we present the X-ray crystal structure at 3.5 A resolution of the pig renal Na+,K+-ATPase with two rubidium ions bound (as potassium congeners) in an occluded state in the transmembrane part of the alpha-subunit. Several of the residues forming the cavity for rubidium/potassium occlusion in the Na+,K+-ATPase are homologous to those binding calcium in the Ca2+-ATPase of sarco(endo)plasmic reticulum. The beta- and gamma-subunits specific to the Na+,K+-ATPase are associated with transmembrane helices alphaM7/alphaM10 and alphaM9, respectively. The gamma-subunit corresponds to a fragment of the V-type ATPase c subunit. The carboxy terminus of the alpha-subunit is contained within a pocket between transmembrane helices and seems to be a novel regulatory element controlling sodium affinity, possibly influenced by the membrane potential. 相似文献
29.
Enterotypes of the human gut microbiome 总被引:6,自引:0,他引:6
Arumugam M Raes J Pelletier E Le Paslier D Yamada T Mende DR Fernandes GR Tap J Bruls T Batto JM Bertalan M Borruel N Casellas F Fernandez L Gautier L Hansen T Hattori M Hayashi T Kleerebezem M Kurokawa K Leclerc M Levenez F Manichanh C Nielsen HB Nielsen T Pons N Poulain J Qin J Sicheritz-Ponten T Tims S Torrents D Ugarte E Zoetendal EG Wang J Guarner F Pedersen O de Vos WM Brunak S Doré J;MetaHIT Consortium Antolín M Artiguenave F Blottiere HM Almeida M Brechot C Cara C Chervaux C Cultrone A 《Nature》2011,473(7346):174-180
Our knowledge of species and functional composition of the human gut microbiome is rapidly increasing, but it is still based on very few cohorts and little is known about variation across the world. By combining 22 newly sequenced faecal metagenomes of individuals from four countries with previously published data sets, here we identify three robust clusters (referred to as enterotypes hereafter) that are not nation or continent specific. We also confirmed the enterotypes in two published, larger cohorts, indicating that intestinal microbiota variation is generally stratified, not continuous. This indicates further the existence of a limited number of well-balanced host-microbial symbiotic states that might respond differently to diet and drug intake. The enterotypes are mostly driven by species composition, but abundant molecular functions are not necessarily provided by abundant species, highlighting the importance of a functional analysis to understand microbial communities. Although individual host properties such as body mass index, age, or gender cannot explain the observed enterotypes, data-driven marker genes or functional modules can be identified for each of these host properties. For example, twelve genes significantly correlate with age and three functional modules with the body mass index, hinting at a diagnostic potential of microbial markers. 相似文献
30.
A prerequisite for life is the ability to maintain electrochemical imbalances across biomembranes. In all eukaryotes the plasma membrane potential and secondary transport systems are energized by the activity of P-type ATPase membrane proteins: H+-ATPase (the proton pump) in plants and fungi, and Na+,K+-ATPase (the sodium-potassium pump) in animals. The name P-type derives from the fact that these proteins exploit a phosphorylated reaction cycle intermediate of ATP hydrolysis. The plasma membrane proton pumps belong to the type III P-type ATPase subfamily, whereas Na+,K+-ATPase and Ca2+-ATPase are type II. Electron microscopy has revealed the overall shape of proton pumps, however, an atomic structure has been lacking. Here we present the first structure of a P-type proton pump determined by X-ray crystallography. Ten transmembrane helices and three cytoplasmic domains define the functional unit of ATP-coupled proton transport across the plasma membrane, and the structure is locked in a functional state not previously observed in P-type ATPases. The transmembrane domain reveals a large cavity, which is likely to be filled with water, located near the middle of the membrane plane where it is lined by conserved hydrophilic and charged residues. Proton transport against a high membrane potential is readily explained by this structural arrangement. 相似文献