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51.
Corine Vernet Joëlle Boretto Marie-Geneviève Mattéi Masahide Takahashi Lucinda J. W. Jack Ian H. Mather Sylvie Rouquier Pierre Pontarotti 《Journal of molecular evolution》1993,37(6):600-612
Summary During a search for novel coding sequences within the human MHC class I region (chromosome 6p21.3), we found an exon (named B30-2) coding for a 166-amino-acid peptide which is very similar to the C-terminal domain of several coding sequences: human 52-kD Sjögren's syndrome nuclear antigen A/Ro (SS-A/Ro) and ret finger protein (RFP), Xenopus nuclear factor 7 (XNF7), and bovine butyrophilin. The first three of these proteins share similarities over the whole length of the molecule whereas butyrophilin is similar in the C-terminal domain. The N-terminal domain of butyrophilin is similar to rat myelin/oligodendrocyte glycoprotein (MOG) and chicken B blood group system (B-G) protein. These domains are components of a new subfamily of the immunoglobulin superfamily (IgSF). Butyrophilin is thus a mosaic protein composed of the MOG/B-G Ig-like domain and the C-terminal domain of 52-kD SS-A/Ro, RFP, and XNF7 (1330-2-like domain). Moreover, in situ hybridization shows that RFP, butyrophilin, and MOG map to the human chromosome 6p2l.3-6p22 region and are thus close to the MHC class I genes. It is therefore possible that the butyrophilin gene is the product of an exon shuffling event which occurred between ancestors of the RFP and MOG genes. To our knowledge, this is the first example of the colocalization of a chimeric gene and its putative progenitors. Finally, regulatory protein T-lymphocyte 1 (Rpt-1) shares similarities with the N-terminal halves of RFP, 52-kD SS-A/Ro, and XNF7, but not with the B30-2-like domain. We show that the ancestral Rpt-l gene evolved by overprinting.
Correspondence to: P. Pontarotti 相似文献
52.
Noboru Sueoka 《Journal of molecular evolution》1993,37(2):137-153
Using a general form of the directional mutation theory, this paper analyzes the effect of mutations in mutator genes on the
G + C content of DNA, the frequency of substitution mutations, and evolutionary changes (cumulative mutations) under various
degrees of selective constraints. Directional mutation theory predicts that when the mutational bias between A/T and G/C nucleotide
pairs is equilibrated with the base composition of a neutral set of DNA nucleotides, the mutation frequency per gene will
be much lower than the frequency immediately after the mutator mutation takes place. This prediction explains the wide variation
of the DNA G + C content among unicellular organisms and possibly also the wide intragenomic heterogeneity of third codon
positions for the genes of multicellular eukaryotes. The present analyses lead to several predictions that are not consistent
with a number of the frequently held assumptions in the field of molecular evolution, including belief in a constant rate
of evolution, symmetric branching of phylogenetic trees, the generality of higher mutation frequency for neutral sets of nucleotides,
the notion that mutator mutations are generally deleterious because of their high mutation rates, and teleological explanations
of DNA base composition.
Presented at the NATO Advanced Research Workshop onGenome Organization and Evolution, Spetsai, Greece, 16–22 September 1992 相似文献
53.
54.
Several genera of N2-fixing bacteria establish symbiotic associations with plants. Among these, the genus Rhizobium has the most significant contribution, in terms of yield, in many important crop plants. The establishment of the Rhizobium-legume symbiosis is a very complex process involving many genes which need to be co-ordinately regulated. In the first instance, plant signal molecules, known to be flavonoids, trigger the expression of host-specific genes in the bacterial partner through the action of the regulatory NodD protein. In response to these signals, Rhizobium bacteria synthesize lipo-oligosaccharide molecules which in turn cause cell differentiation and nodule development. Once the nodule has formed, Rhizobium cells differentiate into bacteroids and another set of genes is activated. These genes, designated nif and fix, are responsible for N2 fixation. In this system, several regulatory proteins are involved in a complex manner, the most important being NifA and a two component (FixK and FixL) regulatory system. Our knowledge about the establishment of these symbioses has advanced recently, although there are many questions yet to be solved. 相似文献
55.
56.
小麦Kr基因在小麦与玉米或鸭茅状摩擦禾杂交中的失活 总被引:2,自引:0,他引:2
用37个小麦(Triticumaestivum)品种(系)为母本,分别与黑麦(Secalecereale)、球茎大麦(Hordeumbulbosum)、玉米(Zeamays)和鸭茅状摩擦禾(Tripsacumdactyloides)杂交,比较其亲和性,小麦和玉米或鸭茅状摩擦禾杂交比小麦与黑麦或球茎大麦杂交的亲和性显著提高。携带着显性Kr1和Kr2基因的小麦品种Hope与黑麦杂交,不能形成胚,而与玉米及鸭茅状摩擦禾杂交时,成胚率分别达16.00%和32.50%。表明控制小麦与黑麦及球茎大麦杂交亲和性的Kr基因系统在小麦与玉米及小麦与鸭茅状摩擦禾属间杂交中失活。讨论了还存在有其它控制小麦属间杂交亲和性的遗传调控系统的可能性。 相似文献
57.
Rapid typing of truffle mycorrhizal roots by PCR amplification of the ribosomal DNA spacers 总被引:4,自引:0,他引:4
DNA analyses were developed to type mycorrhizas of two Tuber species of commercial value (T. melanosporum, T. borchii) and a competitive fungus (Sphaerosporella brunnea) which forms ectomycorrhizas with plants usually considered hosts for truffles. Polymerase chain reaction (PCR) amplification
of DNA isolated from fruitbodies, mycelia, mycorrhizas and leaves of host plants, was performed with a primer pair for an
internal transcribed spacer ITS1-4. ITS amplification followed by restriction fragment length polymorphism (RFLP) analysis
of the amplified products clearly distinguished the two Tuber species at the fruitbody, mycorrhiza and mycelium levels.
Accepted: 6 September 1996 相似文献
58.
A. Guivarc'h J. C. Caissard A. Azmi T. Elmayan D. Chriqui M. Tepfer 《Transgenic research》1996,5(5):281-288
Among the methods now available to localize the sites of gene expression in plant materials, reporter genes based on thegus (uidA) gene ofEscherichia coli, which encodes a -glucuronidase (E.C. 3.2.1.31; GUS), have been the most widely used during the last ten years. The apparent simplicity of the histochemical GUS assay has been a major factor in the increase in articles usinggus genes. However, over the last four years, there have been occasional reports expressing doubts concerning the specificity of the observed localizations based on discrepancies between results obtained with GUS histochemistry and immunocytochemistry and/orin situ hybridization. This brief review compares the results obtained with immunocytochemistry with those obtained with various GUS substrates for histochemical studies. Certain sources of artefact are discussed, as are the limits that should be imposed on interpretation of GUS histochemistry results at the organ, tissue and cell levels. 相似文献
59.
小麦返白系与不同基因型小麦品种杂交后代IPO表达的研究 总被引:3,自引:1,他引:2
以小麦返白系和对照矮变1号以及返白系与各不同生态类型的冬性、半冬性、春性小麦的杂交、回交F1、F2代为材料,研究这些不同基因型品种在返白期间过氧化物酶同工酶(IPO)基因表达模式的动态变化特点。结果表明,在返白期间以返白系为母本的各杂交、回交品种的白化苗中,IPO的个别酶分子表现了可逆的基因阻遏和去阻遏的表达现象。这种表达特点在正、反杂交后F1代中表现一致,从遗传模式上分别属于质-核互作型的分子遗 相似文献
60.
Identification of New Oligodendrocyte- and Myelin-Specific Genes by a Differential Screening Approach 总被引:4,自引:2,他引:2
N. Schaeren-Wiemers C. Schaefer D. M. Valenzuela G. D. Yancopoulos M. E. Schwab 《Journal of neurochemistry》1995,65(1):10-22
Abstract: We have isolated several new genes that are specifically expressed by oligodendrocytes in the CNS. This was achieved by differential screening of a rat spinal cord cDNA library with probes derived from normal and from oligodendrocyte-free spinal cord mRNAs. Four of these genes are exclusively expressed by oligodendrocytes: Three of these are not related to known genes, whereas one encodes the myelin oligodendrocyte glycoprotein (MOG). Four other genes are expressed by oligodendrocytes as well as by Schwann cells. One gene codes for apolipoprotein D, which is thought to be involved in lipid metabolism. A second cDNA sequence codes for the recently identified galactosylceramide-synthesizing enzyme UDP-galactose:ceramide galactosyl-transferase. The third gene encodes a small protein with four putative transmembrane domains that is related to a T-lymphocyte-specific membrane protein, MAL. The fourth gene encodes the rat homologue of the stearyl-CoA-desaturase 2 (SCD2) gene, which is specifically expressed in the nervous system and involved in the synthesis and regulation of long-chain unsaturated fatty acids essential for myelination. Finally, we found that a member of the β-tubulin family is highly expressed in oligodendrocytes as well as neurons. The identification of several new proteins that may play a role in myelin synthesis and sheath formation will lead to new insight into this complex mechanism. 相似文献