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91.
Evolution of the primary and secondary structures of the E1a mRNAs of the adenovirus 总被引:1,自引:0,他引:1
In this paper we investigate and compare (evolutionary) patterns in the
primary and secondary structure of four homologous E1a mRNAs of the
adenovirus. Our main results are as follows: (1) The similarity of the
coding regions of the mRNA sequences reflects both similarity in function
(i.e., oncogenicity) and evolutionary divergence. (2) The similarity of the
leader and the trailer regions reflects host specificity (i.e., human or
simian) and must therefore arise from convergence. (3) Minimal energy
foldings of the mRNAs show similar secondary structures (in particular
around the splice sites). The conservation of pre-mRNA secondary structure
shows that mRNAs are subject to selection constraints in addition to those
associated with proteins. (4) The conserved secondary (helical) structures
consist of nonhomologous subsequences, i.e., shifts have occurred. The
observed shifts near the splice sites seem to be the simplest way of
dealing with the dual constraints.
相似文献
92.
Complete sequences of the rRNA genes of Drosophila melanogaster 总被引:19,自引:0,他引:19
In this, the first of three papers, we present the sequence of the
ribosomal RNA (rRNA) genes of Drosophila melanogaster. The gene regions of
D. melanogaster rDNA encode four individual rRNAs: 18S (1,995 nt), 5.8S
(123 nt), 2S (30 nt), and 28S (3,945 nt). The ribosomal DNA (rDNA) repeat
of D. melanogaster is AT rich (65.9% overall), with the spacers being
particularly AT rich. Analysis of DNA simplicity reveals that, in contrast
to the intergenic spacer (IGS) and the external transcribed spacer (ETS),
most of the rRNA gene regions have been refractory to the action of
slippage-like events, with the exception of the 28S rRNA gene expansion
segments. It would seem that the 28S rRNA can accommodate the products of
slippage-like events without loss of activity. In the following two papers
we analyze the effects of sequence divergence on the evolution of (1) the
28S gene "expansion segments" and (2) the 28S and 18S rRNA secondary
structures among eukaryotic species, respectively. Our detailed analyses
reveal, in addition to unequal crossing-over, (1) the involvement of
slippage and biased mutation in the evolution of the rDNA multigene family
and (2) the molecular coevolution of both expansion segments and the
nucleotides involved with compensatory changes required to maintain
secondary structures of RNA.
相似文献
93.
A new species of Sabellaria is described from the southeast coast of Brazil and compared with related species known from South or North America. 相似文献
94.
95.
L6 skeletal muscle myoblasts stably overexpressing glucose transporter GLUT1 or GLUT4 with exofa- cial myc-epitope tags were characterized for their response to insulin. In clonally selected cultures, 2-deoxyglucose uptake into L6-GLUT1myc myoblasts and myotubes was linear within the time of study. In L6-GLUT1myc and L6-GLUT4myc myoblasts, 100 nmol/L insulin treatment increased the GLUT1 content of the plasma membrane by 1.58±0.01 fold and the GLUT4 content 1.96±0.11 fold, as well as the 2-deoxyglucose uptake 1.53±0.09 and 1.86±0.17 fold respectively, all by a wortmannin-inhibitable manner. The phosphorylation of Akt in these two cell lines was increased by insulin. L6-GLUT1myc myoblasts showed a dose-dependent stimulation of glucose uptake by insulin, with unaltered sensitiv- ity and maximal responsiveness compared with wild type cells. By contrast, the improved insulin re- sponsiveness and sensitivity of glucose uptake were observed in L6-GLUT4myc myoblasts. Earlier studies indicated that forskolin might affect insulin-stimulated GLUT4 translocation. A 65% decrease of insulin-stimulated 2-deoxyglucose uptake in GLUT4myc cells was not due to an effect on GLUT4 mobi- lization to the plasma membrane, but instead on direct inhibition of GLUT4. Forskolin and dipyridamole are more potent inhibitors of GLUT4 than GLUT1. Alternatively, pentobarbital inhibits GLUT1 more than GLUT4. The use of these inhibitors confirmed that the overexpressed GLUT1 or GLUT4 are the major functional glucose transporters in unstimulated and insulin-stimulated L6 myoblasts. Therefore, L6-GLUT1myc and L6-GLUT4myc cells provide a platform to screen compounds that may have differ- ential effects on GLUT isoform activity or may influence GLUT isoform mobilization to the cell surface of muscle cells. 相似文献
96.
JESSICA M. DA SILVA JOHN S. DONALDSON GAIL REEVES TERRY A. HEDDERSON 《Biological journal of the Linnean Society. Linnean Society of London》2012,105(2):293-308
Declining populations of less than 250 mature individuals are symptomatic of many Critically Endangered cycads, which, globally, comprise the most threatened group of organisms as a result of collecting and habitat loss. Survival plans focus on law enforcement, reintroduction, and augmentation programmes using plants from the wild and botanical gardens. Augmentation is one of the few remaining options for cycad populations, although the assumed benefits remain untested and there is a possibility that augmentation from different sources could compromise the genetic integrity of existing populations, especially when garden plants have no provenance data. We studied Encephalartos latifrons, a South African endemic, which is a typical Critically Endangered cycad. We studied the extent and structure of genetic diversity in wild and ex situ populations to assess the potential benefits and risks associated with augmentation programmes. We examined 86 plants using amplified fragment length polymorphisms (AFLPs). The 417 AFLP markers thus generated yielded a unique DNA ‘fingerprint’ for each plant. Wild populations retain high levels of genetic diversity and this is reflected among the ex situ holdings at the Kirstenbosch Botanical Garden. No population differentiation is evident, indicating a single panmictic population, consistent with moderately high levels of gene flow between subpopulations and a sexual mode of reproduction. Bayesian clustering identified four genotype groups in the wild, as well as a genotype group only found in ex situ collections. Our results indicate that E. latifrons would benefit from augmentation programmes, including the use of undocumented collections, and careful management of breeding plants would increase the heterogeneity of propagules. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 105 , 293–308. 相似文献
97.
甜瓜幼苗叶片光合变化特性 总被引:3,自引:1,他引:2
为探讨甜瓜光响应变化特性与环境因子的关系,选择光响应曲线适宜测定的时段,以甜瓜幼苗为试材,将1 d分为3个时段:10:00-12:00、12:00-15:00和15:00-17:00,每个叶位叶片测定1 d,并采用直角双曲线修正模型拟合光响应曲线,研究不同时段下甜瓜叶片光响应曲线、光响应参数的变化趋势和不同叶位叶片光响应参数特性。结果表明:当环境中光合有效辐射增强,叶面温度(Tl)升高,空气相对湿度(RH)降低;当环境中光合有效辐射减弱,Tl降低,RH升高。10:00-12:00光响应曲线和12:00-15:00的第1-4叶光响应曲线呈双曲线,在强光下趋向饱和状况,12:00-15:00的第5叶光合速率和15:00-17:00光合速率在强光下出现明显的光抑制现象。1 d的不同时段均表现为10:00-12:00最大净光合速率(Pmax)和光饱和点(LSP)最高,12:00-17:00降低;12:00-15:00光补偿点(LCP)和暗呼吸速率(Rd)较高,其它两个时段较低,10:00-17:00光补偿点量子效率(φc)、气孔导度(Gs)和胞间CO2浓度(Ci)总体呈降低趋势,气孔限制值(Ls)升高。10:00-15:00相同时段测得的不同叶位叶片光响应参数,以第4-5叶光合性能较好,15:00-17:00以第3叶Pmax最高,第5叶次之;10:00-17:00 Gs和Ci以第5叶较低,第1叶较高,Ls以第5叶较高,第1叶较低。RH为影响Pmax的主要决策因子,测定时段、叶面饱和蒸汽压亏缺(Vpdl)和Tl为主要限制因子。10:00-12:00适宜进行光响应曲线测定,气孔限制为不同时段光合作用不同的主要因素,非气孔限制为影响不同叶位叶片光合作用的主要因素。 相似文献
98.
ANDREA FERREIRA DA COSTA PABLO JOSÉ FRANCISCO PENA RODRIGUES MARIA DAS GRAÇAS LAPA WANDERLEY 《Botanical journal of the Linnean Society. Linnean Society of London》2009,159(1):163-181
The species related to Vriesea paraibica (Bromeliaceae, Tillandsioideae) have controversial taxonomic limits. For several decades, this group has been identified in herbarium collections as V. × morreniana, an artificial hybrid that does not grow in natural habitats. The aim of this study was to assess the morphological variation in the V. paraibica complex through morphometric analyses of natural populations. Two sets of analyses were performed: the first involved six natural populations (G1) and the second was carried out on taxa that emerged from the first analysis, but using material from herbarium collections (G2). Univariate ANOVA was used, as well as discriminant analysis of 16 morphometric variables in G1 and 18 in G2. The results of the analyses of the two groups were similar and led to the selection of diagnostic traits of four species. Lengths of the lower and median floral bracts were significant for the separation of red and yellow floral bracts. Vriesea paraibica and V. interrogatoria have red bracts; these two species are differentiated by the widths of the lower and median portions of the inflorescence and by scape length. These structures are larger in the former and smaller in the latter. Of the species with yellow floral bracts, V. eltoniana is distinguished by longer leaf blades and scapes and V. flava is characterized by its shorter sepal lengths. © 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 159 , 163–181. 相似文献
99.
Abstract: The hitherto poorly known, monotypic trilobite genus Fenestraspis from the Lower Devonian of Bolivia is revised and its original assignment to the Synphoriinae supported. The thoracic morphology of the genus remains very poorly known. Fenestraspis is morphologically unusual because of the development of extensive fenestrae in the pleural region of the pygidium and apparently of the thorax; the presence of upwardly directed spines on the cephalon, thorax and pygidium; and the exceptionally large and highly elevated eyes with the palpebral rim projecting outwards above the visual surface. The function of the fenestrae remains uncertain. If they formed openings in the body of the trilobite in life they may have allowed circulation of oxygenated water to the limb exites so that respiration could have been maintained while the trilobite was enrolled. If they were covered with a flexible membrane, they may have been secondary respiratory structures or had a sensory function. The Synphoriinae is regarded as a subfamily of the Dalmanitidae rather than as an independent family of the Dalmanitoidea as proposed by some authors. The type species of the poorly known monotypic genus Dalmanitoides from the Lower Devonian of Argentina is illustrated photographically for the first time and compared with Fenestraspis . 相似文献
100.
Lopes DM DA Silva FO Fernandes Salomão TM Campos LA Tavares MG 《Molecular ecology resources》2009,9(3):923-925
Eight microsatellite primers were developed from ISSR (intersimple sequence repeats) markers for the stingless bee Melipona rufiventris. These primers were tested in 20 M. rufiventris workers, representing a single population from Minas Gerais state. The number of alleles per locus ranged from 2 to 5 (mean = 2.63) and the observed and expected heterozygosity values ranged from 0.00 to 0.44 (mean = 0.20) and from 0.05 to 0.68 (mean = 0.31), respectively. Several loci were also polymorphic in M. quadrifasciata, M. bicolor, M. mandacaia and Partamona helleri and should prove useful in population studies of other stingless bees. 相似文献