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941.
Nathaniel L. Clark Joe Gasper Masashi Sekino Stevan A. Springer Charles F. Aquadro Willie J. Swanson 《PLoS genetics》2009,5(7)
Reproductive proteins are among the fastest evolving in the proteome, often due to the consequences of positive selection, and their rapid evolution is frequently attributed to a coevolutionary process between interacting female and male proteins. Such a process could leave characteristic signatures at coevolving genes. One signature of coevolution, predicted by sexual selection theory, is an association of alleles between the two genes. Another predicted signature is a correlation of evolutionary rates during divergence due to compensatory evolution. We studied female–male coevolution in the abalone by resequencing sperm lysin and its interacting egg coat protein, VERL, in populations of two species. As predicted, we found intergenic linkage disequilibrium between lysin and VERL, despite our demonstration that they are not physically linked. This finding supports a central prediction of sexual selection using actual genotypes, that of an association between a male trait and its female preference locus. We also created a novel likelihood method to show that lysin and VERL have experienced correlated rates of evolution. These two signatures of coevolution can provide statistical rigor to hypotheses of coevolution and could be exploited for identifying coevolving proteins a priori. We also present polymorphism-based evidence for positive selection and implicate recent selective events at the specific structural regions of lysin and VERL responsible for their species-specific interaction. Finally, we observed deep subdivision between VERL alleles in one species, which matches a theoretical prediction of sexual conflict. Thus, abalone fertilization proteins illustrate how coevolution can lead to reproductive barriers and potentially drive speciation. 相似文献
942.
943.
Swanson BO Anderson SP Digiovine C Ross RN Dorsey JP 《Integrative and comparative biology》2009,49(1):21-31
Spider silk is a high-performance biomaterial with exceptional mechanical properties and over half a century of research into its mechanics, structure, and biology. Recent research demonstrates that it is a highly variable class of materials that differs across species and individuals in complex and interesting ways. Here, we review recent literature on mechanical variation and evolution in spider silk. We then present new data on material properties of silk from nine species of spiders in the Mesothelae and Mygalomorphae, the two basal clades of spiders. Silk from spiders in the Araneomorphae (true spiders where most previous research on silk has focused) is significantly stronger and therefore much tougher than the silk produced by spiders in the basal groups. These data support the hypothesis that the success and diversity seen in araneomorph spiders is associated with the evolution of this high-performance fiber. This comparative approach shows promise as a way to understand complex, high-performance biomaterials. 相似文献
944.
Dawn M. E. Bowdish Kaori Sakamoto Mi-Jeong Kim Mariliis Kroos Subhankar Mukhopadhyay Cynthia A. Leifer Karl Tryggvason Siamon Gordon David G. Russell 《PLoS pathogens》2009,5(6)
Virtually all of the elements of Mycobacterium tuberculosis (Mtb) pathogenesis, including pro-inflammatory cytokine production, granuloma formation, cachexia, and mortality, can be induced by its predominant cell wall glycolipid, trehalose 6,6′-dimycolate (TDM/cord factor). TDM mediates these potent inflammatory responses via interactions with macrophages both in vitro and in vivo in a myeloid differentiation factor 88 (MyD88)-dependent manner via phosphorylation of the mitogen activated protein kinases (MAPKs), implying involvement of toll-like receptors (TLRs). However, specific TLRs or binding receptors for TDM have yet to be identified. Herein, we demonstrate that the macrophage receptor with collagenous structure (MARCO), a class A scavenger receptor, is utilized preferentially to “tether” TDM to the macrophage and to activate the TLR2 signaling pathway. TDM-induced signaling, as measured by a nuclear factor-kappa B (NF-κB)-luciferase reporter assay, required MARCO in addition to TLR2 and CD14. MARCO was used preferentially over the highly homologous scavenger receptor class A (SRA), which required TLR2 and TLR4, as well as their respective accessory molecules, in order for a slight increase in NF-κB signaling to occur. Consistent with these observations, macrophages from MARCO−/− or MARCO−/−SRA−/− mice are defective in activation of extracellular signal-related kinase 1/2 (ERK1/2) and subsequent pro-inflammatory cytokine production in response to TDM. These results show that MARCO-expressing macrophages secrete pro-inflammatory cytokines in response to TDM by cooperation between MARCO and TLR2/CD14, whereas other macrophage subtypes (e.g. bone marrow–derived) may rely somewhat less effectively on SRA, TLR2/CD14, and TLR4/MD2. Macrophages from MARCO−/− mice also produce markedly lower levels of pro-inflammatory cytokines in response to infection with virulent Mtb. These observations identify the scavenger receptors as essential binding receptors for TDM, explain the differential response to TDM of various macrophage populations, which differ in their expression of the scavenger receptors, and identify MARCO as a novel component required for TLR signaling. 相似文献
945.
Renée Guérin Cynthia Turcotte Alexandre Leroux & Luis A. Rokeach 《FEMS yeast research》2009,9(8):1250-1259
Yeasts have evolved numerous responsive pathways to survive in fluctuating and stressful environments. The endoplasmic reticulum (ER) is sensitive to adverse conditions, which are detected by response pathways to ensure correct protein folding. Calnexin is an ER transmembrane chaperone acting in both quality control of folding and response to persistent stress. Calnexin is a key protein required for viability in certain organisms such as mammals and the fission yeast Schizosaccharomyces pombe . Nevertheless, S. pombe calnexin-independent (Cin) cells were obtained after transient expression of a particular calnexin mutant. The Cin state is dominant, is stably propagated by an epigenetic mechanism and segregates in a non-Mendelian fashion to the meiotic progeny. The nucleolar protein Cif1p was identified as an inducer of the Cin state in a previous genetic screen. Here, we report the identification of novel inducers isolated in an overexpression genetic screen: pyruvate kinase (Pyk1p) and phosphoglycerate kinase (Pgk1p). Addition of pyruvate, the end product of pyruvate kinase and glycolysis, also induced calnexin independence in a dose-dependent manner. Remarkably, growth in respiration media or cold temperatures induced the appearance of Cin cells at high frequencies. Taken together, our results indicate that the Cin state can be triggered by extracellular changes, suggesting that this state represents an epigenetic adaptative response to environmental modifications. 相似文献
946.
Spread of an invasive grass in closed-canopy deciduous forests across local and regional environmental gradients 总被引:1,自引:0,他引:1
Cynthia D. Huebner 《Biological invasions》2010,12(7):2081-2089
Establishment of Microstegium vimineum, an invasive exotic grass, in closed-canopy U.S. eastern forests was evaluated across a local (roadside to forest interior)
and regional (across two geographic provinces) environmental gradient in West Virginia. The two geographic provinces were
the Allegheny Plateau (more mesic) and the Ridge and Valley Province (more xeric). Biotic, abiotic, and disturbance variables
were measured in (1) systematically located plots, starting from the roadside and extending 50 m into the forests, and (2)
randomly selected, forest interior plots, with equal numbers of plots containing or not containing M. vimineum. Associations between the variables and the presence of M. vimineum at both scales were evaluated using generalized linear models. Relative importance of the variables related to M. vimineum establishment in the forest interior plots at the regional scale was determined using logistic regression. Results confirmed
Microstegium vimineum’s reduced reproductive capacity in the forest interior compared to the roadside. Patches of M. vimineum in the forest interiors across the regional gradient were best defined by high native plant richness and diversity. Greater
canopy opening, more moss, and shallower litter depths were also positively and significantly associated with M. vimineum presence, but only during the driest sample year. 相似文献
947.
948.
Synthesis and SAR of novel histamine H3 receptor antagonists 总被引:1,自引:0,他引:1
Jesudason CD Beavers LS Cramer JW Dill J Finley DR Lindsley CW Stevens FC Gadski RA Oldham SW Pickard RT Siedem CS Sindelar DK Singh A Watson BM Hipskind PA 《Bioorganic & medicinal chemistry letters》2006,16(13):3415-3418
The synthesis and biological evaluation of novel tetrahydroisoquinoline, tetrahydroquinoline, and tetrahydroazepine antagonists of the human and rat H(3) receptors are described. The substitution around these rings as well as the nature of the substituent on nitrogen is explored. Several compounds with high affinity and selectivity for the human and rat H(3) receptors are reported. 相似文献
949.
Swanson DM Wilson SJ Boggs JD Xiao W Apodaca R Barbier AJ Lovenberg TW Carruthers NI 《Bioorganic & medicinal chemistry letters》2006,16(4):897-900
Aplysamine-1 (1), a marine natural product, was synthesized and screened for in vitro activity at the human and rat histamine H3 receptors. Aplysamine-1 (1) was found to possess a high binding affinity for the human H3 receptor (Ki = 30+/-4 nM). Synthetic analogs of 1, including des-bromoaplysamine-1 (10) and dimethyl-{2-[4-(3-piperidin-1-yl-propoxy)-phenyl]-ethyl}-amine (13), were potent H3 antagonists. 相似文献
950.
Finley DR Bell MG Borel AG Bloomquist WE Cohen ML Heiman ML Kriauciunas A Matthews DP Miles T Neel DA Rito CJ Sall DJ Shuker AJ Stephens TW Tinsley FC Winter MA Jesudason CD 《Bioorganic & medicinal chemistry letters》2006,16(21):5691-5694
The synthesis and biological evaluation of a series of benzimidazolone beta(3) adrenergic receptor agonists are described. A trend toward the reduction of rat atrial tachycardia upon increasing steric bulk at the 3-position of the benzimidazolone moiety was observed. 相似文献