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171.
We sequenced the entire control region and portions of flanking genes
(tRNA(Phe), tRNA(Glu), and ND6) in the common chaffinch (Fringilla
coelebs), blue chaffinch (F. teydea), brambling (F. montifringilla), and
greenfinch (Carduelis chloris). In these finches the control region is
similar in length (1,223-1,237 bp) and has the same flanking gene order as
in other birds, and contains a putative TAS element and the highly
conserved CSB-1 and F, D, and C boxes recognizable in most vertebrates.
Cloverleaf-like structures associated with the TAS element at the 5' end
and CSB-1 at the 3' end of the control region may be involved with the stop
and start of D-loop synthesis, respectively. The pattern of nucleotide and
substitution bias is similar to that in other vertebrates, and consequently
the finch control region can be subdivided into a central, conserved G-rich
domain (domain II) flanked by hypervariable 5'-C-rich (domain I) and
3'-AT-rich (domain III) segments. In pairwise comparisons among finch
species, the central domain has unusually low transition/transversion
ratios, which suggests that increased G + T content is a functional
constraint, possibly for DNA primase efficiency. In finches the relative
rates of evolution vary among domains according to a ratio of 4.2 (domain
III) to 2.2 (domain I) to 1 (domain II), and extensively among sites within
domains I and II. Domain I and III sequences are extremely useful in
recovering intraspecific phylogeographic splits between populations in
Africa and Europe, Madeira, and a basal lineage in Nefza, Tunisia. Domain
II sequences are highly conserved, and are therefore only useful in
conjunction with sequences from domains I and III in phylogenetic studies
of closely related species.
相似文献
172.
DDX4 (VASA) is an RNA helicase expressed in the germ cells of all animals. To gain greater insight into the role of this gene in mammalian germ cell development, we characterized DDX4 in both a marsupial (the tammar wallaby) and a monotreme (the platypus). DDX4 is highly conserved between eutherian, marsupial, and monotreme mammals. DDX4 protein is absent from tammar fetal germ cells but is present from Day 1 postpartum in both sexes. The distribution of DDX4 protein during oogenesis and spermatogenesis in the tammar is similar to eutherians. Female tammar germ cells contain DDX4 protein throughout all stages of postnatal oogenesis. In males, DDX4 is in gonocytes, and during spermatogenesis it is present in spermatocytes and round spermatids. A similar distribution of DDX4 occurs in the platypus during spermatogenesis. There are several DDX4 isoforms in the tammar, resulting from both pre- and posttranslational modifications. DDX4 in marsupials and monotremes has multiple splice variants and polyadenylation motifs. Using in silico analyses of genomic databases, we found that these previously unreported splice variants also occur in eutherians. In addition, several elements implicated in the control of Ddx4 expression in the mouse, including RGG (arginine-glycine-glycine) and dimethylation of arginine motifs and CpG islands within the Ddx4 promoter, are also highly conserved. Collectively these data suggest that DDX4 is essential for the regulation of germ cell proliferation and differentiation across all three extant mammalian groups-eutherians, marsupials, and monotremes. 相似文献
173.
瑞典国家财产委员会拥有骑士岛的所有权与管理权,并计划对该岛上所有的公共空间进行更新和开发,以提高其可达性与吸引力。该项目的核心是找到一种更新和修复岛屿的方法,从而在尊重历史价值的同时满足现代功能需求。对骑士岛南部的改造是岛上公共空间更新的第一部分。设计的关键条件是沿滨水区域创造可以供人步行与停坐的大面积空间,并在保持开放海港氛围的同时,对旧的道路铺装进行管理。设计者设计了一套灵活使用公共空间的综合解决方案,将开放空间与之前的码头一样,沿着水滨的形态进行布局。 相似文献
174.
Allosteric antagonism of insect odorant receptor ion channels 总被引:1,自引:0,他引:1
Jones PL Pask GM Romaine IM Taylor RW Reid PR Waterson AG Sulikowski GA Zwiebel LJ 《PloS one》2012,7(1):e30304
Background
At a molecular level, insects utilize members of several highly divergent and unrelated families of cell-surface chemosensory receptors for detection of volatile odorants. Most odors are detected via a family of odorant receptors (ORs), which form heteromeric complexes consisting of a well-conserved OR co-receptor (Orco) ion channel and a non-conserved tuning OR that provides coding specificity to each complex. Orco functions as a non-selective cation channel and is expressed in the majority of olfactory receptor neurons (ORNs). As the destructive behaviors of many insects are principally driven by olfaction, Orco represents a novel target for behavior-based control strategies. While many natural and synthetic odorants have been shown to agonize Orco/Or complexes, only a single direct Orco modulator, VUAA1, has been described. In an effort to identify additional Orco modulators, we have investigated the structure/activity relationships around VUAA1.Results
A search of our compound library identified several VUAA1 analogs that were selected for evaluation against HEK cells expressing Orco from the malaria vector Anopheles gambiae (AgOrco). While the majority of compounds displayed no activity, many of these analogs possess no intrinsic efficacy, but instead, act as competitive VUAA1 antagonists. Using calcium mobilization assays, patch clamp electrophysiology, and single sensillum in vivo recording, we demonstrate that one such candidate, VU0183254, is a specific allosteric modulator of OR signaling, capable of broadly inhibiting odor-mediated OR complex activation.Conclusions
We have described and characterized the first Orco antagonist, that is capable of non-competitively inhibiting odorant-evoked activation of OR complexes, thereby providing additional insight into the structure/function of this unique family of ligand-gated ion channels. While Orco antagonists are likely to have limited utility in insect control programs, they represent important pharmacological tools that will facilitate the investigation of the molecular mechanisms underlying insect olfactory signal transduction. 相似文献175.
ABSTRACT: Co-evolving positions within protein sequences have been used as spatial constraints to develop a computational approach for modeling membrane protein structures. 相似文献
176.
Andrew J Pask Natalie E Calatayud Geoff Shaw William M Wood Marilyn B Renfree 《BMC biology》2010,8(1):113
Background
Hormones are critical for early gonadal development in nonmammalian vertebrates, and oestrogen is required for normal ovarian development. In contrast, mammals determine sex by the presence or absence of the SRY gene, and hormones are not thought to play a role in early gonadal development. Despite an XY sex-determining system in marsupial mammals, exposure to oestrogen can override SRY and induce ovarian development of XY gonads if administered early enough. Here we assess the effect of exogenous oestrogen on the molecular pathways of mammalian gonadal development. 相似文献177.
178.
Relocation of a Ca2+-dependent protein kinase activity during pollen tube reorientation 总被引:9,自引:0,他引:9 下载免费PDF全文
Pollen tube reorientation is a dynamic cellular event that is crucial for successful fertilization. We have shown previously that pollen tube orientation is regulated by cytosolic free calcium ([Ca2+]c). In this paper, we studied the activity of a Ca2+-dependent protein kinase during reorientation. The kinase activity was assayed in living cells by using confocal ratio imaging of BODIPY FL bisindolylmaleimide. We found that growing pollen tubes exhibited higher protein kinase activity in the apical region, whereas nongrowing cells showed uniform distribution. Modification of growth direction by diffusion of inhibitors/activators from a micropipette showed the spatial redistribution of kinase activity to predict the new growth orientation. Localized increases in [Ca2+]c induced by photolysis of caged Ca2+ that led to reorientation also increased kinase activity. Molecular and immunological assays suggest that this kinase may show some functional homology with protein kinase C. We suggest that the tip-localized gradient of kinase activity promotes Ca2+-mediated exocytosis and may act to regulate Ca2+ channel activity. 相似文献
179.
Gordon Pask 《Bulletin of mathematical biology》1965,27(1):261-273
Systems in which a human subject interacts with an adaptive control mechanism through display and response facilities are
examined. A cybernetic model is discussed, together with supporting experimental data.
The research reported in this paper has been supported by the Air Force Office of Scientific Research, under Contract AF.
61.052.640. (for Cybernetic models for learning) and by the Aerospace Medical Research Laboratories A.F.C.S., under contract
AF. 61.052.402. (for adaptive teaching systems), through the European Office for Aerospace Research. 相似文献
180.