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131.
Variation in heat shock proteins within tropical and desert species of poeciliid fishes 总被引:8,自引:0,他引:8
Norris CE; diIorio PJ; Schultz RJ; Hightower LE 《Molecular biology and evolution》1995,12(6):1048-1062
The 70-kilodalton heat shock protein (hsp70) family of molecular
chaperones, which contains both stress-inducible and normally abundant
constitutive members, is highly conserved across distantly related taxa.
Analysis of this protein family in individuals from an outbred population
of tropical topminnows, Poeciliopsis gracilis, showed that while
constitutive hsp70 family members showed no variation in protein isoforms,
inducibly synthesized hsp70 was polymorphic. Several species of
Poeciliopsis adapted to desert environments exhibited lower levels of
inducible hsp70 polymorphism than the tropical species, but constitutive
forms were identical to those in P. gracilis, as they were in the
confamilial species Gambusia affinis. These differences suggest that
inducible and constitutive members of this family are under different
evolutionary constraints and may indicate differences in their function
within the cell. Also, northern desert species of Poeciliopsis synthesize a
subset of the inducible hsp70 isoforms seen in tropical species. This
distribution supports the theory that ancestral tropical fish migrated
northward and colonized desert streams; the subsequent decrease in
variation of inducible hsp70 may have been due to genetic drift or a
consequence of adaptation to the desert environment. Higher levels of
variability were found when the 30- kilodalton heat shock protein (hsp30)
family was analyzed within different strains of two desert species of
Poeciliopsis and also in wild-caught individuals of Gambusia affinis. In
both cases the distribution of hsp30 isoform diversity was similar to that
seen previously with allozyme polymorphisms.
相似文献
132.
Interest in the use of low-copy nuclear genes for phylogenetic analyses of
plants has grown rapidly, because highly repetitive genes such as those
commonly used are limited in number. Furthermore, because low- copy genes
are subject to different evolutionary processes than are plastid genes or
highly repetitive nuclear markers, they provide a valuable source of
independent phylogenetic evidence. The gene for granule-bound starch
synthase (GBSSI or waxy) exists in a single copy in nearly all plants
examined so far. Our study of GBSSI had three parts: (1) Amino acid
sequences were compared across a broad taxonomic range, including grasses,
four dicotyledons, and the microbial homologs of GBSSI. Inferred structural
information was used to aid in the alignment of these very divergent
sequences. The informed alignments highlight amino acids that are conserved
across all sequences, and demonstrate that structural motifs can be highly
conserved in spite of marked divergence in amino acid sequence. (2)
Maximum-likelihood (ML) analyses were used to examine exon sequence
evolution throughout grasses. Differences in probabilities among
substitution types and marked among-site rate variation contributed to the
observed pattern of variation. Of the parameters examined in our set of
likelihood models, the inclusion of among-site rate variation following a
gamma distribution caused the greatest improvement in likelihood score. (3)
We performed cladistic parsimony analyses of GBSSI sequences throughout
grasses, within tribes, and within genera to examine the phylogenetic
utility of the gene. Introns provide useful information among very closely
related species, but quickly become difficult to align among more divergent
taxa. Exons are variable enough to provide extensive resolution within the
family, but with low bootstrap support. The combined results of amino acid
sequence comparisons, maximum-likelihood analyses, and phylogenetic studies
underscore factors that might affect phylogenetic reconstruction. In this
case, accommodation of the variable rate of evolution among sites might be
the first step in maximizing the phylogenetic utility of GBSSI.
相似文献
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136.
Of all the terminal electron acceptors, Fe(III) is the most naturally abundant in many subsurface environments. Fe(III)-reducing microorganisms are phylogenetically diverse and have been isolated from a variety of sources. Unlike most electron acceptors, Fe(III) has a very low solubility and is usually present as insoluble oxides at neutral pH. The mechanisms by which microorganisms access and reduce insoluble Fe(III) are poorly understood. Initially, it was considered that microorganisms could only reduce insoluble Fe(III) through direct contact with the oxide. However, recent studies indicate that extracellular electron shuttling or Fe(III)-chelating compounds may alleviate the need for cell–oxide contact. These include microbially secreted compounds or exogenous electron shuttling agents, mainly from humic substances. Electron shuttling via humic substances is likely a significant process for Fe(III) reduction in subsurface environments. This paper reviews the various mechanisms by which Fe(III) reduction may be occurring in pure culture and in soils and sediments. 相似文献
137.
Soluble methane monooxygenase (sMMO) can degrade many chlorinated and aromatic pollutants. It is produced by certain methanotrophs such as Methylosinus trichosporium when grown on methane under copper limitation but, due to its low aqueous solubility, methane cannot support dense biomass growth. Since it is water soluble, methanol may be a more attractive growth substrate, but it is widely believed that sMMO is not produced on methanol. In this study, when the growth-limiting substrate was switched from methane to methanol, in the presence of the particulate MMO inhibitor, allylthiourea, growth of M. trichosporium OB3b continued unabated and sMMO activity was completely retained. When allylthiourea was then removed, sMMO activity was maintained for an additional 24 generations, albeit at a slightly lower level due to the presence of 0.70 microM of Cu(2+) in the feed medium. While a biomass density of only 2 g l(-1) could be obtained on methane, 7.4 g l(-1) was achieved by feeding methanol exponentially, and 29 g l(-1) was obtained using a modified feeding strategy employing on-line carbon dioxide production measurement. It was concluded that methanol can be employed to produce large amounts of M. trichosporium biomass containing sMMO. 相似文献
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139.
Laura Eggertson Noni MacDonald Cindy L. Baldassi Paul C. Hébert Ken Flegel Joan Ramsay 《CMAJ》2009,181(12):E265-E266
140.
Piya Lahiry Jian Wang John F. Robinson Jacob P. Turowec David W. Litchfield Matthew B. Lanktree Gregory B. Gloor Erik G. Puffenberger Kevin A. Strauss Mildred B. Martens David A. Ramsay C. Anthony Rupar Victoria Siu Robert A. Hegele 《American journal of human genetics》2009,84(2):134-147
Six infants in an Old Order Amish pedigree were observed to be affected with endocrine-cerebro-osteodysplasia (ECO). ECO is a previously unidentified neonatal lethal recessive disorder with multiple anomalies involving the endocrine, cerebral, and skeletal systems. Autozygosity mapping and sequencing identified a previously unknown missense mutation, R272Q, in ICK, encoding intestinal cell kinase (ICK). Our results established that R272 is conserved across species and among ethnicities, and three-dimensional analysis of the protein structure suggests protein instability due to the R272Q mutation. We also demonstrate that the R272Q mutant fails to localize at the nucleus and has diminished kinase activity. These findings suggest that ICK plays a key role in the development of multiple organ systems. 相似文献