共查询到20条相似文献,搜索用时 15 毫秒
1.
There are two tightly linked loci (D and CE) for the human Rh blood group. Their gene products are membrane proteins having
12 transmembrane domains and form a complex with Rh50 glycoprotein on erythrocytes. We constructed phylogenetic networks of
human and nonhuman primate Rh genes, and the network patterns suggested the occurrences of gene conversions. We therefore
used a modified site-by-site reconstruction method by using two assumed gene trees and detected 9 or 11 converted regions.
After eliminating the effect of gene conversions, we estimated numbers of nonsynonymous and synonymous substitutions for each
branch of both trees. Whichever gene tree we selected the branch connecting hominoids and Old World monkeys showed significantly
higher nonsynonymous than synonymous substitutions, an indication of positive selection. Many other branches also showed higher
nonsynonymous than synonymous substitutions; this suggests that the Rh genes have experienced some kind of positive selection.
Received: 16 March 1999 / Accepted: 17 June 1999 相似文献
2.
Ferritin, a protein widespread in nature, concentrates iron ∼1011–1012-fold above the solubility within a spherical shell of 24 subunits; it derives in plants and animals from a common ancestor
(based on sequence) but displays a cytoplasmic location in animals compared to the plastid in contemporary plants. Ferritin
gene regulation in plants and animals is altered by development, hormones, and excess iron; iron signals target DNA in plants
but mRNA in animals. Evolution has thus conserved the two end points of ferritin gene expression, the physiological signals
and the protein structure, while allowing some divergence of the genetic mechanisms. Comparison of ferritin gene organization
in plants and animals, made possible by the cloning of a dicot (soybean) ferritin gene presented here and the recent cloning
of two monocot (maize) ferritin genes, shows evolutionary divergence in ferritin gene organization between plants and animals
but conservation among plants or among animals; divergence in the genetic mechanism for iron regulation is reflected by the
absence in all three plant genes of the IRE, a highly conserved, noncoding sequence in vertebrate animal ferritin mRNA. In
plant ferritin genes, the number of introns (n= 7) is higher than in animals (n= 3). Second, no intron positions are conserved when ferritin genes of plants and animals are compared, although all ferritin
gene introns are in the coding region; within kingdoms, the intron positions in ferritin genes are conserved. Finally, secondary
protein structure has no apparent relationship to intron/exon boundaries in plant ferritin genes, whereas in animal ferritin
genes the correspondence is high. The structural differences in introns/exons among phylogenetically related ferritin coding
sequences and the high conservation of the gene structure within plant or animal kingdoms suggest that kingdom-specific functional
constraints may exist to maintain a particular intron/exon pattern within ferritin genes. In the case of plants, where ferritin
gene intron placement is unrelated to triplet codons or protein structure, and where ferritin is targeted to the plastid,
the selection pressure on gene organization may relate to RNA function and plastid/nuclear signaling.
Received: 25 July 1995 / Accepted: 3 October 1995 相似文献
3.
4.
The sequences of the entire blue opsin gene in the squirrel monkey (Saimiri boliviensis) and the five introns of the human blue opsin gene were obtained. Intron 3 of these genes contains an Alu sequence and intron
4 contains a partial mer13 sequence. A comparison of the squirrel monkey opsin sequence with published mammalian opsin sequences
shows that features believed to be functionally critical are all conserved. However, the blue opsin has evolved twice as fast
as rhodopsin and is only as conservative as the β globin, which has evolved at the average rate of mammalian proteins. Interestingly,
the interhelical loops are, on average, actually more conservative than the transmembrane α helical regions. The introns of
the blue opsin gene have evolved at the average rate of introns in primate genes.
Received: 5 August 1996 / Accepted: 2 October 1996 相似文献
5.
6.
7.
Takehiro Kusakabe Isato Araki Noriyuki Satoh William R. Jeffery 《Journal of molecular evolution》1997,44(3):289-298
The origin and evolutionary relationship of actin isoforms was investigated in chordates by isolating and characterizing
two new ascidian cytoplasmic and muscle actin genes. The exon–intron organization and sequences of these genes were compared
with those of other invertebrate and vertebrate actin genes. The gene HrCA1 encodes a cytoplasmic (nonmuscle)-type actin, whereas the MocuMA2 gene encodes an adult muscle-type actin. Our analysis of these genes showed that intron positions are conserved among the
deuterostome actin genes. This suggests that actin gene families evolved from a single actin gene in the ancestral deuterostome.
Sequence comparisons and molecular phylogenetic analyses also suggested a close relationship between the ascidian and vertebrate
actin isoforms. It was also found that there are two distinct lineages of muscle actin isoforms in ascidians: the larval muscle
and adult body-wall isoforms. The four muscle isoforms in vertebrates show a closer relationship to each other than to the
ascidian muscle isoforms. Similarly, the two cytoplasmic isoforms in vertebrates show a closer relationship to each other
than to the ascidian and echinoderm cytoplasmic isoforms. In contrast, the two types of ascidian muscle actin diverge from
each other. The close relationship between the ascidian larval muscle actin and the vertebrate muscle isoforms was supported
by both neighbor-joining and maximum parsimony analyses. These results suggest that the chordate ancestor had at least two
muscle actin isoforms and that the vertebrate actin isoforms evolved after the separation of the vertebrates and urochordates.
Received: 20 June 1996 / Accepted: 16 October 1996 相似文献
8.
9.
Jean-Luc Da Lage Maurice Wegnez Marie-Louise Cariou 《Journal of molecular evolution》1996,43(4):334-347
While the two amylase genes of Drosophila melanogaster are intronless, the three genes of D. pseudoobscura harbor a short intron. This raises the question of the common structure of the Amy gene in Drosophila species. We have investigated the presence or absence of an intron in the amylase genes of 150 species
of Drosophilids. Using polymerase chain reaction (PCR), we have amplified a region that surrounds the intron site reported
in D. pseudoobscura and a few other species. The results revealed that most species contain an intron, with a variable size ranging from 50 to
750 bp, although the very majoritary size was around 60–80 bp. Several species belonging to different lineages were found
to lack an intron. This loss of intervening sequence was likely due to evolutionarily independent and rather frequent events.
Some other species had both types of genes: In the obscura group, and to a lesser extent in the ananassae subgroup, intronless copies had much diverged from intron-containing genes. Base composition of short introns was found to
be variable and correlated with that of the surrounding exons, whereas long introns were all A-T rich. We have extended our
study to non-Drosophilid insects. In species from other orders of Holometaboles, Lepidoptera and Hymenoptera, an intron was
found at an identical position in the Amy gene, suggesting that the intron was ancestral.
Received: 23 October 1995 / Accepted: 5 March 1996 相似文献
10.
11.
Boldogköi Z 《Journal of molecular evolution》2000,51(6):600-606
The question whether the noncoding DNA strand had or still has the capability for encoding functional polypeptides has been
addressed in several articles. The theoretical background of the views advocating this idea arose from two groups of findings.
One of them was based on various observations implying that the genetic code was adapted for double-strand coding. The other
group of theories arose from the observation of gene-length overlapping open reading frames (O-ORFs) on the antisense DNA
strand in a number of genes. In fact, the above theories, which I term selectionist, conceive a novel conception of gene evolution,
proposing that new genes can be created by the utilization of antisense DNA strand. In contrast, neutralist theory claims
that the O-ORFs are mere by-products of evolutionary processes acting to create special codon usage and base distribution
patterns in the coding sequences.
Received: 16 June 2000 / Accepted: 31 August 2000 相似文献
12.
Alexander E. Vinogradov 《Journal of molecular evolution》1999,49(3):376-384
The intron–genome size relationship was studied across a wide evolutionary range (from slime mold and yeast to human and
maize), as well as the relationship between genome size and the ratio of intervening/coding sequence size. The average intron
size is scaled to genome size with a slope of about one-fourth for the log-transformed values; i.e., on the global scale its
increase in evolution is lower than the increase in genome size by four orders of magnitude. There are exceptions to the general
trend. In baker's yeast introns are extraordinarily long for its genome size. Tetrapods also have longer introns than expected
for their genome sizes. In teleost fish the mean intron size does not differ significantly, notwithstanding the differences
in genome size. In contrast to previous reports, avian introns were not found to be significantly shorter than introns of
mammals, although avian genomes are smaller than genomes of mammals on average by about a factor of 2.5. The extra-/intragenic
ratio of noncoding DNA can be higher in fungi than in animals, notwithstanding the smaller fungal genomes. In vertebrates
and invertebrates taken separately, this ratio is increasing as the increase in genome size. Two hypotheses are proposed to
explain the variation in the extra-/intragenic ratio of noncoding DNA in organisms with similar numbers of genes: transition
(dynamic) and equilibrium (static). According to the transition model, this variation arises with the rapid shift of genome
size because the bulk of extragenic DNA can be changed more rapidly than the finely interspersed intron sequences. The equilibrium
model assumes that this variation is a result of selective adjustment of genome size with constraints imposed on the intron
size due to its putative link to chromatin structure (and constraints of the splicing machinery).
Received: 23 October 1997 / Accepted: 14 April 1999 相似文献
13.
The human RH locus is responsible for the expression of the Rh blood group antigens. It consists of two closely linked genes, RHD and RHCE, that exhibit 92% similarity between coding regions. These observations suggest that they are derived from a relatively recent duplication event. Previously a study of nonhuman primate RH-like genes demonstrated that ancestral RH gene duplication occurred in the common ancestor of man, chimpanzees and gorillas. By amplification of intron 3 and intron 4 of gorilla RH-like genes, we have now shown that, like man, gorillas possess two types of RH intron 3 (RHCE intron 3 being 289 bp longer than the RHD intron 3) and two types of intron 4 (RHCE intron 4 being 654 bp longer than the RHD intron 4). Here we report the characterization of a cDNA encoded by a gorilla RH-like gene which possesses introns 3 and 4 of the RHCE type. A comparison of this gorilla RHCE-like coding sequence with previously characterized human and ape cDNA sequences suggests that RH genes experienced complex recombination events after duplication in the common ancestor of humans, chimpanzees and gorillas. 相似文献
14.
15.
It has been hypothesized that a large fraction of 24% noncoding DNA in R. prowazekii consists of degraded genes. This hypothesis has been based on the relatively high G+C content of noncoding DNA. However,
a comparison with other genomes also having a low overall G+C content shows that this argument would also apply to other bacteria.
To test this hypothesis, we study the coding potential in sets of genes, pseudogenes, and intergenic regions. We find that
the correlation function and the χ2-measure are clearly indicative of the coding function of genes and pseudogenes. However, both coding potentials make almost
no indication of a preexisting reading frame in the remaining 23% of noncoding DNA. We simulate the degradation of genes due
to single-nucleotide substitutions and insertions/deletions and quantify the number of mutations required to remove indications
of the reading frame. We discuss a reduced selection pressure as another possible origin of this comparatively large fraction
of noncoding sequences.
Received: 27 December 1999 / Accepted: 5 July 2000 相似文献
16.
Mashiguchi K Urakami E Hasegawa M Sanmiya K Matsumoto I Yamaguchi I Asami T Suzuki Y 《Plant & cell physiology》2008,49(2):178-190
Arabinogalactan proteins (AGPs) are hydroxyproline-rich glycoproteins present at the plasma membrane and in extracellular spaces. A synthetic chemical, beta-glucosyl Yariv reagent (beta-GlcY), binds specifically to AGPs. We previously reported that gibberellin signaling is specifically inhibited by beta-GlcY treatment in barley aleurone protoplasts. In the present study, we found that beta-GlcY also inhibited gibberellin-induced programmed cell death (PCD) in aleurone cells. We examined the universality and specificity of the inhibitory effect of beta-GlcY on gibberellin signaling using microarray analysis and found that beta-GlcY was largely effective in repressing gibberellin-induced gene expression. In addition, >100 genes were up-regulated by beta-GlcY in a gibberellin-independent manner, and many of these were categorized as defense-related genes. Defense signaling triggered by several defense system inducers such as jasmonic acid and a chitin elicitor could inhibit gibberellin-inducible events such as alpha-amylase secretion, PCD and expression of some gibberellin-inducible genes in aleurone cells. Furthermore, beta-GlcY repressed the gibberellin-inducible Ca2+-ATPase gene which is important for gibberellin-dependent gene expression, and induced known repressors of gibberellin signaling, two WRKY genes and a NAK kinase gene. These effects of beta-GlcY were also phenocopied by the chitin elicitor and/or jasmonic acid. These results indicate that gibberellin signaling is under the regulation of defense-related signaling in aleurone cells. It is also probable that AGPs are involved in the perception of stimuli causing defense responses. 相似文献
17.
18.
The evolutionary relationship of muscle and nonmuscle actin isoforms in deuterostomia was studied by the isolation and characterization
of two actin genes from the cephalochordate Branchiostoma lanceolatum and two from the hemichordate Saccoglossus kowalevskii The Branchiostoma genes specify a muscle and a nonmuscle actin type, respectively. Together with earlier results on muscle actins from vertebrates
and urochordates, a N-terminal sequence signature is defined for chordate muscle actins. These diagnostic amino acid residues
separate the chordates from the echinoderms and other metazoa. Although the two Saccoglossus actins characterized so far lack the diagnostic residues, in line with the presumptive phylogenetic position of hemichordates
outside the chordates, a definitive conclusion can only be expected once the full complement of actin genes of Saccoglossus is established. Comparison of the intron patterns of the various deuterostomic actin genes shows that intron 330-3, which
is present in all vertebrate genes, is conspicuously absent from nonvertebrate genes. The possible origin of this intron is
discussed.
Received: 4 July 1997 / Accepted: 29 August 1997 相似文献
19.
Hiroshi Wada Mari Kobayashi Riki Sato Nori Satoh Hitoshi Miyasaka Yoshihisa Shirayama 《Journal of molecular evolution》2002,54(1):118-128
To test the validity of intron–exon structure as a phylogenetic marker, the intron–exon structure of EF-1α genes was investigated
for starfish, acornworms, ascidians, larvaceans, and amphioxus and compared with that of vertebrates. Of the 11 distinct intron
insertion sites found within the coding regions of the deuterostome EF-1α genes, 7 are shared by several taxa, while the remainder
are unique to certain taxa. Examination of the shared introns of the deuterostome EF-1α gene revealed that independent intron
loss or intron insertion must have occurred in separate lineages of the deuterostome taxa. Maximum parsimony analysis of the
intron–exon data matrix recovered five parsimonious trees (consistency index = 0.867). From this result, we concluded that
the intron–exon structure of deuterostome EF-1α has evolved more dynamically than previously thought, rendering it unsuitable
as a phylogenetic marker. We also reconstructed an evolutionary history of intron insertion–deletion events on the deuterostome
phylogeny, based on several molecular phylogenetic studies. These analyses revealed that the deuterostome EF-1α gene has lost
individual introns more frequently than all introns simultaneously. 相似文献