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11.
Abstract Species of Trillium have a disjunct distribution occurring in both North America and eastern Asia. In North America all 36 species are diploid. The 11 species of eastern Asia, however, include only a single diploid with all the other species being polyploids. Why do different patterns of speciation develop in North America and in eastern Asia? The breeding systems of populations in the North American T. erectum, T. grandiflorum and T. ovatum , and in Asian T. kamtschaticum were investigated by estimating the inbreeding coefficient from cold-induced banding patterns which reveal homozygotes and heterozygotes. From the analyses of the inbreeding coefficients, T. erectum, T. grandiflorum and the Pacific coastal species, T. ovatum are predominantly inbreeding species. T. ovatum populations from the Rocky Mountain region are outbreeders. However the Japanese species, T. kamtschaticum has a mixture of outbreeding and inbreeding among populations. The development of polyploid systems in Asia is possibly the result of the diversity of the breeding systems among the populations. The shift from outbreeding to inbreeding appears to be an important key step in the occurrence of poliploids by hybridization between the different species. 相似文献
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Structure and pre-B lymphocyte restricted expression of the VpreB in humans and conservation of its structure in other mammalian species. 总被引:11,自引:1,他引:10
DNA from several mammals, including humans, was found to contain one or more restriction enzyme digested DNA fragments which hybridized to the mouse VpreB gene under stringencies demonstrating at least 70% nucleotide sequence homologies, indicating that the VpreB locus may be widespread and highly conserved among mammals. A human VpreB genomic clone was isolated and sequenced. Two exons and the intervening intron are spaced almost identically as in the mouse VpreB1 gene, and show 76% sequence homology to the mouse gene. As in the mouse VpreB1 gene, the 5' end of the human VpreB gene contains characteristic features of Ig domains, while the 3' end is Ig non-related. This 3' Ig non-related structure of the VpreB gene(s) may, therefore, have existed before the speciation of humans and mice over 65 million years ago. Sequences encoding the entire putative second framework region and a stretch in the third framework region are identical in human and mouse VpreB. the human VpreB gene appears to be selectively expressed in human pre-B cell lines as an 0.85 kb poly(A)+ RNA. Its expression promises to be a useful marker for the detection of normal and malignant human pre-B lymphocytes. 相似文献
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Ichiro Yamato Hiro Nakamura Hiroshi Murakami Yasuhiro Anraku 《FEMS microbiology letters》1988,56(1):21-27
Abstract The cybB gene on a plasmid encoding cytochrome b 561 in Escherichia coli was disrupted by insertion of Kmrl determinant DNA. The cromosomal cybB gene was replaced by the inactivated cybB gene on the plasmid by homologous recombination using λ phage lysogenization and heat-induction. The replacement was confirmed by Southern and Western blotting analyses. Deficiency on the cybB gene product did not affect the growth properties of the cells, and the oxidase activities of the cells dependent on various substrates were similar to those of the parental strain. Cytochrome b 561 is concluded to be expressed in E. coli , but may not play a major role in cell growth. In the genetic map of E. coli , the cybB gene was determined by conjugational and transductional crosses to be at 31 min between trg and terC . 相似文献
14.
Hiro Nakamura Hiroshi Murakami Ichiro Yamato Yasuhiro Anraku 《Molecular & general genetics : MGG》1988,212(1):1-5
Summary The complete nucleotide sequence of the Escherichia coli cybB gene for diheme cytochrome b
561 and its flanking region was determined. The cybB gene comprises 525 nucleotides and encodes a 175 amino acid polypeptide with a molecular weight of 20160. From its deduced amino acid sequence, cytochrome b
561 is predicted to be very hydrophobic (polarity 33.7%) and to have three membrane spanning regions. Histidines, canonical ligand residues for protohemes, are localized in these regions, and the heme pockets are thought to be in the cytoplasmic membrane. No significant homology of the primary structure of cytochrome b
561 with those of other bacterial b-type cytochromes was observed. 相似文献
15.
Characterisation of Non-Uniform Photosynthesis Induced by Abscisic Acid in Leaves Having Different Mesophyll Anatomies 总被引:29,自引:0,他引:29
Terashima Ichiro; Wong Suan-Chin; Osmond C. Barry; Farquhar Graham D. 《Plant & cell physiology》1988,29(3):385-394
The effects of abscisic acid (ABA) on photosynthesis in leavesof Helianthus annuus L. were compared with those in leaves ofVicia faba L. After the ABA treatment, the response of photosyntheticCO2 assimilation rate, A, to calculated intercellular partialpressure of CO2, Pi, (A(pi) relationship) was markedly depressedin H. annuus. A less marked depression was also observed inV.faba. However, when the abaxial epidermes were removed fromthese leaves, neither the maximum rate nor the CO2 responseof photosynthetic oxygen evolution was affected by the applicationof ABA. Starch-iodine tests revealed that photosynthesis was not uniformover the leaves of H. annuus treated with ABA. The starch contentwas diffferent in each bundle sheath extension compartment (thesmallest subdivision of mesophyll by veins with bundle sheathextensions, having an area of ca. 0.25 mm2 and ca. 50 stomata).In some compartments, no starch was detected. The distributionof open stomata, examined using the silicone rubber impressiontechniques, was similar to the pattern of starch accumulation.In V.faba leaves, which lack bundle sheath extensions, distributionof starch was more homogeneous. These results indicate that the apparent non-stomatal inhibitionof photosynthesis by ABA deduced from the depression of A(pi)relationship is an artifact which can be attributed to the non-uniformdistribution of transpiration and photosynthesis over the leaf.Intercellular gaseous environment in the ABA-treated leavesis discussed in relation to mesophyll anatomy.
1 Present address: Department of Botany, Duke University, Durham,NC 27706, U.S.A. (Received September 30, 1987; Accepted January 13, 1988) 相似文献
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Terashima Ichiro; Sonoike Kintake; Kawazu Tamotsu; Katoh Sakae 《Plant & cell physiology》1991,32(8):1275-1283
To examine the effects of chilling of leaves of cucumber (Cucumissativus L.) in moderate light on the coupling state of thylakoidsin situ, changes in fluorescence, changes in light scatteringand flash-induced changes in absorbance at 518 nm were examinedin intact leaves. After chilling of leaves at 5?C in the lightfor 5 h, the non-photochemical quenching of fluorescence, ameasure of energisation of thylakoids, was largely suppressed.The treatment also caused a suppression of light-induced changesin the light scattering by leaves, which depends on the formationof a pH gradient across thylakoid membranes. When thylakoidswere prepared by very gentle methods from the leaves chilledin the light, through a step of preparation of intact chloro-plasts,the transport of electrons from H2O to ferricyanide was uncoupled,being insensitive to an uncoupler, methylamine. These data provide consistent evidence that the thylakoids areuncoupled in situ by the chilling of leaves in the light and,as a consequence of the uncoupling, the energisation of themembranes is suppressed. However, the decay of the flash-inducedchange in absorbance at 518 nm in leaves was not markedly acceleratedby the treatment. The thylakoids isolated from leaves chilledin the light, which were in the uncoupled state, also did notshow a rapid decay, unless an efficient uncoupler such as gramicidinwas added. These results suggest that even a considerable uncouplingof thylakoids, brought about by chilling of leaves in the light,is not sufficient to cause a marked acceleration of the decayof the flash-induced change in absorbance at 518 nm. Therefore,analysis at 518 nm is not always a sensitive method for assessingthe coupling state of thylakoids. (Received July 1, 1991; Accepted October 4, 1991) 相似文献
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