SEARCH · PubMed Health

Results for “Introgression”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 811 records · Page 45Linked to original sources

PubMed1999

Two blood pressure/cardiac mass quantitative trait loci on chromosome 3 in Dahl rats.

Interval mapping was used to identify putative quantitative trait loci (QTL) for blood pressure and cardiac mass on Chromosome (Chr) 3 in F1(S x R) x S population of 150 rats raised on an 8% NaCl diet. Two genetic markers 95.7 cM apart, D3Wox3 and D3Mco5 (tightly linked to Edn3), showed "suggestive" linkage to blood pressure (LOD = 2.0 and 1.8 respectively). In addition, D3Wox3 showed "suggestive" linkage to heart weight (LOD = 2.5), and D3Mco5 showed "suggestive" linkage to body weight-adjusted heart weight (LOD = 2.1). Congenic rats (designated S.R-Edn3) were constructed by introgressing the R-rat Edn3 allele (and flanking loci) into the S strain. On a 2% NaCl diet, S.R-Edn3 rats had lower blood pressure (21.4 mm Hg, P = 0. 0005) and heart weight (59 mg, P = 0.0038) compared with S rats, confirming the existence of a blood pressure QTL on Chr 3 near Edn3 even though QTL linkage analysis of blood pressure did not achieve stringent statistical criteria for significance. The results of the congenic experiment and the large distance between the two putative QTL suggest the presence of at least two independent blood pressure/cardiac mass QTL detectable on Chr 3 in the Dahl rat model of genetic hypertension.

Analysis of Variance↗

PubMed2000

Probing meiosis in hybrids of Lolium (Poaceae) with a discriminatory repetitive genomic sequence.

A moderately repetitive genomic DNA sequence (designated pLPBB2-123) derived from Lolium perenne L. (Poaceae) is considerably more abundant in the genome of this species than in that of the closely related L. temulentum. The repetitive sequence probe is clearly able to discriminate between the genomic DNA of both species in Southern analysis, and effectively 'paints' only the chromosome set of L. perenne in diploid and triploid hybrids with L. temulentum. Fluorescence in situ hybridisation of this sequence onto homologous chromosomes during meiosis I of the hybrids shows that the sequence is evenly distributed along all of the chromosomes of L. perenne and appears to have little effect on the structural integrity or recombination potential of hybrid bivalents. Discrimination between chromatin of different parental origin in hybrid bivalents shows for the first time a progressive relaxation of relational coiling of homoeologues throughout meiotic prophase. It also highlights structural irregularities that can now be unequivocally assigned to the longer chromosomes of L. temulentum. The advantages of the use of specific differentially amplified sequences instead of whole genome probes are discussed within the context of introgression breeding programmes within the Lolium/Festuca complex.

Chromosomes↗

PubMed2005

Genetic characterization of asymmetric somatic hybrids between Bupleurum scorzonerifolium Willd and Triticum aestivum L.: potential application to the study of the wheat genome.

In this paper, we describe how Bupleurum scorzonerifolium/Triticum aestivum asymmetric somatic hybrids can be exploited to study the wheat genome. Protoplasts of B. scorzonerifolium Willd were irradiated with ultraviolet light (UV) and fused with protoplasts of common wheat (T. aestivum L.). All cell clones were similar in appearance to those of B. scorzonerifolium, while the regenerated plantlets were either intermediate or B. scorzonerifolium-like. Genotypic screening using isozymes showed that 39.3% of cell clones formed were hybrid. Some of the hybrid cell clones grew vigorously, and differentiated green leaves, shoots or plantlets. DNA marker analysis of the hybrids demonstrated that wheat DNA was integrated into the nuclear genomes of B. scorzonerifolium and in situ karyotyping cells revealed that a few wheat chromosome fragments had been introgressed into B. scorzonerifolium. The average wheat SSR retention frequency of the RH panel was 20.50%, but was only 6.67% in fusions with a non-irradiated donor. B. scorzonerifolium chromosomes and wheat SSR fragments in most asymmetric hybrid cell lines remained stable over a period of 2.5-3.5 years. We suggest the UV-induced asymmetric somatic hybrids between B. scorzonerifolium Willd and T. aestivum L. have the potential for use in the construction of an RH map of the wheat genome.

Bupleurum↗

PubMed2006

Temporally extended gene expression of the ADP-Glc pyrophosphorylase large subunit (AgpL1) leads to increased enzyme activity in developing tomato fruit.

Tomato plants (Solanum lycopersicum) harboring the allele for the AGPase large subunit (AgpL1) derived from the wild species Solanum habrochaites (AgpL1 ( H )) are characterized by higher AGPase activity and increased starch content in the immature fruit, as well as higher soluble solids in the mature fruit following the breakdown of the transient starch, as compared to fruits from plants harboring the cultivated tomato allele (AgpL1 ( E )). Comparisons of AGPase subunit gene expression and protein levels during fruit development indicate that the increase in AGPase activity correlates with a prolonged expression of the AgpL1 gene in the AgpL1 ( H ) high starch line, leading to an extended presence of the L1 protein. The S1 (small subunit) protein also remained for an extended period of fruit development in the AgpL1 ( H ) fruit, linked to the presence of the L1 protein. There were no discernible differences between the kinetic characteristics of the partially purified AGPase-L1(E) and AGPase-L1(H) enzymes. The results indicate that the increased activity of AGPase in the AgpL1 ( H ) tomatoes is due to the extended expression of the regulatory L1 and to the subsequent stability of the heterotetramer in the presence of the L1 protein, implying a role for the large subunit not only in the allosteric control of AGPase activity but also in the stability of the AGPase L1-S1 heterotetramer. The introgression line of S. lycopersicum containing the wild species AgpL1 ( H ) allele is a novel example of transgressive heterosis in which the hybrid multimeric enzyme shows higher activity due to a modulated temporal expression of one of the subunits.

Alleles↗

PubMed2007

Origin of seed shattering in rice (Oryza sativa L.).

A critical evolutionary step during rice domestication was the elimination of seed shattering. Wild rice disperses seeds freely at maturity to guarantee the propagation, while cultivated rice retains seeds on the straws to make easy harvest and decrease the loss of production. The molecular basis for this key event during rice domestication remains to be elucidated. Here we show that the seed shattering is controlled by a single dominant gene, Shattering1 (SHA1), encoding a member of the trihelix family of plant-specific transcription factors. SHA1 was mapped to a 5.5 kb genomic fragment, which contains a single open reading frame, using a backcrossed population between cultivated rice Teqing and an introgression line IL105 with the seed shattering habit derived from perennial common wild rice, YJCWR. The predicted amino acid sequence of SHA1 in YJCWR and IL105 is distinguished from that in eight domesticated rice cultivars, including Teqing, by only a single amino acid substitution (K79N) caused by a single nucleotide change (g237t). Further sequence verification on the g237t mutation site revealed that the g237t mutation is present in all the domesticated rice cultivars, including 92 indica and 108 japonica cultivars, but not in any of the 24 wild rice accessions examined. Our results demonstrate that the g237t mutation in SHA1 accounts for the elimination of seed shattering, and that all the domesticated rice cultivars harbor the mutant sha1 gene and therefore have lost the ability to shed their seeds at maturity. In addition, our data support the theory that the non-shattering trait selection during rice domestication occurred prior to the indica-japonica differentiation in rice evolutionary history.

Amino Acid Sequence↗

PubMed1998

Genetic diversity in porcine Oesophagostomum dentatum and O. quadrispinulatum and their delineation by isoenzyme analysis.

The genetic diversity in eight strains of Oesophagostomum dentatum and O. quadrispinulatum was investigated by the electrophoresis study of ten enzyme systems. The loci Idh-2, Fbp, Sdh, and Pgm were found to be diagnostic between the species examined. Both the proportion of fixed allelic differences (26.3%) and the genetic distance coefficient (D = 0.54) are well above the range for differentiation of valid species. Isoenzyme patterns of susceptible and resistant lines of O. dentatum showed at polymorphic loci a reduced genetic heterogeneity in the latter group. No qualitative difference in terms of the presence/absence of alleles was observed among susceptible and resistant isolates with the enzymes studied. The detection of one possible hybrid indicates that introgression in O. dentatum and O. quadrispinuatum may occur.

Alleles↗

PubMed2001

Two tightly linked QTLs modify tomato sugar content via different physiological pathways.

Congenic lines that differ in a single defined chromosome segment are useful for the study of complex phenotypes, as they allow isolation of the effect of a particular quantitative trait locus (QTL) from those of the entire genome. We conducted high-resolution QTL mapping of a 9-cM introgression, originating from the wild tomato species Lycopersicon pennellii, in two extremely different genetic and physiological backgrounds. In the "indeterminate" glasshouse background we identified only a single QTL ( Brix9-2-5) that affects the total soluble solids of the fruit [mainly sugars, measured in Brix units (B)]. This QTL was previously delimited within the gene for an apoplastic invertase, Lin5, that modulates sugar partitioning to the fruit. Analysis of the effects of the same chromosome segment in "determinate", open-field tomatoes, revealed two QTLs, 0.3 cM apart: the fruit-specific Brix9-2-5 that affects B only, and the shoot-specific PW9-2-5, which accounts for an altered growth habit resulting in increases in plant weight, yield, and B. This study highlights the power of the congenic approach for dissecting developmental pathways leading to complex phenotypes.

Base Sequence↗

PubMed2002

Two broad-spectrum blast resistance genes, Pi9( t) and Pi2( t), are physically linked on rice chromosome 6.

To understand the molecular basis of broad-spectrum resistance to rice blast, fine-scale mapping of the two blast resistance (R) genes, Pi9( t) and Pi2( t), was conducted. These two genes were introgressed from different resistance donors, previously reported to confer resistance to many blast isolates in the Philippines, and were mapped to an approximately 10-cM interval on chromosome 6. To further test their resistance spectrum, 43 blast isolates collected from 13 countries were used to inoculate the Pi2( t) and Pi9( t) plants. Pi9( t)-bearing lines were highly resistant to all isolates tested, and lines carrying Pi2( t) were resistant to 36 isolates, confirming the broad-spectrum resistance of these two genes to diverse blast isolates. Three RAPD markers tightly linked to Pi9( t) were identified using the bulk segregant analysis technique. Twelve positive bacterial artificial chromosome (BAC) clones were identified and a BAC contig covering about 100 kb was constructed when the Pi9( t) BAC library was screened with one of the markers. A high-resolution map of Pi9( t) was constructed using BAC ends. The Pi2( t) gene was tightly linked to all of the Pi9( t) markers in 450 F(2) plants. These data suggest that Pi9( t) and Pi2( t) are either allelic or tightly linked in an approximately 100-kb region. The mapping results for Pi9( t) and Pi2( t) provide essential information for the positional cloning of these two important blast resistance genes in rice.

Chromosomes, Artificial, Bacterial↗

PubMed2005

The recessive potyvirus resistance gene pot-1 is the tomato orthologue of the pepper pvr2-eIF4E gene.

The translation initiation factor 4E (eIF4E) has been implicated in naturally occurring resistance to Potato virus Y (PVY) determined by the pvr2 locus in pepper (Capsicum annuum). Here, the molecular basis of the recessive resistance to PVY and Tobacco etch virus (TEV) controlled by the pot-1 locus in tomato (Lycopersicon esculentum; now Solanum lycopersicum) was investigated. On the basis of genetic mapping data that indicated that pot-1 and pvr2 are located in syntenic regions of the tomato and pepper genomes, the possible involvement of eIF4E in pot-1-mediated resistance was assessed. Genetic mapping of members of the eIF4E multigenic family in tomato introgression lines revealed that an eIF4E locus indeed maps in the same genomic region as pot-1. By comparing eIF4E coding sequences between resistant and susceptible Lycopersicon genotypes, a small number of polymorphisms that co-segregate with the pot-1 locus were identified, suggesting that this gene could be involved in resistance to potyviruses. Functional complementation experiments using Potato virus X-mediated transient expression of eIF4E from a susceptible genotype in a resistant pepper genotype confirmed that a small number of amino acid substitutions in the eIF4E protein indeed account for resistance/susceptibility to both the PVY and TEV, and consequently that pot-1 and pvr2 are orthologues. Taken together, these results support the role of this eIF4E gene as a key component of recessive resistance to potyviruses, and validate the comparative genomic approach for the molecular characterization of recessive resistance genes.

Amino Acid Sequence↗

PubMed2006

A complete physical map of a wild beet (Beta procumbens) translocation in sugar beet.

Two sugar beet lines carry homologous translocations of the wild beet Beta procumbens. Long-range restriction mapping with rare cutting enzymes revealed that both translocations are different in size, however, an overlapping region of about 350 kb could be identified. Both lines are resistant to the beet cyst nematode but only TR520 carries the previously cloned resistance gene Hs1pro-1. Hence, a second gene for nematode resistance (Hs1-1) must be located within this region. A bacterial artificial chromosome (BAC) library was constructed from line TR520. The library was screened with a number of B. procumbens specific probes and 61 BAC clones were identified. Five BAC clones formed a minimal tiling path of 580 kb to cover the overlapping region between both translocations including the translocation breakpoint. The five BACs from the overlapping region and one additional BAC distal from that contig were sequenced. The total sequence length from the five BACs of the overlapping region amounted to 524 kb which is 74.35% of the total insert size of these BACs. The frequency of retrotransposon sequences ranged between 14.7 and 43.3%. A total of 133 ORFs were identified, none of these showed similarity to known disease resistance genes. Of these, 12 ORFs showed homology to genes involved in biotic stress resistance reactions or to transcription factors. This paper demonstrates how genome specific probes can be employed for cloning an alien gene introgression into a cultivated species.

Beta vulgaris↗

PubMed1998

Genetic and physical localization of the root-knot nematode resistance locus mi in tomato.

As part of a map-based cloning strategy designed to isolate the root-knot nematode resistance gene Mi, tomato F2 populations were analyzed in order to identify recombination points close to this economically important gene. A total of 21,089 F2 progeny plants were screened using morphological markers. An additional 1887 F2 were screened using PCR-based flanking markers. Fine-structure mapping of recombinants with newly developed AFLP markers, and RFLP markers derived from physically mapped cosmid subclones, localized Mi to a genomic region of about 550 kb. The low frequency of recombinants indicated that recombination was generally suppressed in these crosses and that crossovers were restricted to particular regions. To circumvent this problem, a population of Lycopersicon peruvianum, the species from which Mi was originally introgressed, that was segregating for resistance was developed. Screening of this population with PCR, RFLP and AFLP markers identified several plants with crossovers near Mi. Recombination frequency was approximately eight-fold higher in the Mi region of the L. peruvianum cross. However, even within the wild species cross, recombination sites were not uniformly distributed in the region. By combining data from the L. esculentum and L. peruvianum recombinant analyses, it was possible to localize Mi to a region of the genome spanning less than 65 kb.

Animals↗

PubMed2001

Genome-wide dissection of Fusarium resistance in tomato reveals multiple complex loci.

Resistance to different pathogenic races of Fusarium oxysporum f. sp. lycopersici (F. o. lycopersici) was explored at two genomic levels in tomato. Six independent Fusarium resistance loci were identified by comparing the responses of a complete set of 53 lines carrying different introgressed regions of the Lycopersicon pennellii genome in a L. esculentum background. The loci confer varying degrees of resistance to different races of the pathogen. Corresponding map positions from different tomato species were aligned and in some cases revealed parallel resistance to F. o. lycopersici with qualitative changes in race specificities. One of the loci identified corresponds to the previously characterized complex resistance locus I2, which is involved in resistance to F. o. lycopersici race 2. A novel member of this locus, I2C-5, which belongs to the NBS-LRR family of resistance genes, was cloned and shown to confer partial resistance in transgenic plants. Thus, at a particular complex locus gene members can confer full or partial resistance to F. o. lycopersici race 2. The results of our whole-genome mapping analysis underline the robust independent origin of resistance to a particular disease and demonstrate the conservation of resistance features at syntenic loci, together with the rapid diversification of genes for innate resistance within loci.

Base Sequence↗

PubMed2004

Contrasting patterns of Y chromosome variation in Ashkenazi Jewish and host non-Jewish European populations.

The molecular basis of more than 25 genetic diseases has been described in Ashkenazi Jewish populations. Most of these diseases are characterized by one or two major founder mutations that are present in the Ashkenazi population at elevated frequencies. One explanation for this preponderance of recessive diseases is accentuated genetic drift resulting from a series of dispersals to and within Europe, endogamy, and/or recent rapid population growth. However, a clear picture of the manner in which neutral genetic variation has been affected by such a demographic history has not yet emerged. We have examined a set of 32 binary markers (single nucleotide polymorphisms; SNPs) and 10 microsatellites on the non-recombining portion of the Y chromosome (NRY) to investigate the ways in which patterns of variation differ between Ashkenazi Jewish and their non-Jewish host populations in Europe. This set of SNPs defines a total of 20 NRY haplogroups in these populations, at least four of which are likely to have been part of the ancestral Ashkenazi gene pool in the Near East, and at least three of which may have introgressed to some degree into Ashkenazi populations after their dispersal to Europe. It is striking that whereas Ashkenazi populations are genetically more diverse at both the SNP and STR level compared with their European non-Jewish counterparts, they have greatly reduced within-haplogroup STR variability, especially in those founder haplogroups that migrated from the Near East. This contrasting pattern of diversity in Ashkenazi populations is evidence for a reduction in male effective population size, possibly resulting from a series of founder events and high rates of endogamy within Europe. This reduced effective population size may explain the high incidence of founder disease mutations despite overall high levels of NRY diversity.

Chromosomes, Human, Y↗

PubMed2005

A complementary method for production of tetraploid Crassostrea gigas using crosses between diploids and tetraploids with cytochalasin b treatments.

We present a new method to produce tetraploid Crassostrea gigas by cytochalasin B inhibition of polar body 2 expulsion in diploid females crossed with tetraploid males. This offers a means of direct introgression of genetic characters from selected diploid to tetraploid lines, avoiding a triploid step. Offspring larval ploidy shifted over time and depended on size, with tetraploids more frequent among the smaller larvae and triploids among the large. Viable tetraploids were found at 4 and 6 months, indicating the technique was successful. The possibility that gynogenesis occurred was tested by microsatellite analysis to confirm the presence of paternally inherited alleles. These were present in all animals of the 2n x 4n + CB (female first) cross. However, a 4n x 2n + CB cross produced triploids, including some gynogens. Our method illustrates for the first time that diploid C. gigas eggs, if selected for large size, can give viable tetraploid offspring.

Animals↗

PubMed2004

Overexpression of mitochondrial genes is caused by interactions between the nucleus of Brassica rapa and the cytoplasm of Diplotaxis muralis in the leaves of alloplasmic lines of B. rapa.

In Brassica species, alloplasmic lines displaying cytoplasmic male sterility (CMS) are established by combining the nucleus from B. rapa with the cytoplasm from Diplotaxis muralis. The failure to observe restriction fragment length polymorphism (RFLP) patterns of mitochondrial genes ( coxII, coxIII, atpA, atp6, atp9, cob, nad3, nad6, and nad9) between alloplasmic lines of B. rapa and D. muralis indicates that introgression of the B. rapa nucleus into the cytoplasm of D. muralis does not cause any alterations in the structure of the mitochondrial genome. To investigate how the nucleus influences the cytoplasm, we examined the expression of mitochondrial genes in the leaves of euplasmic and alloplasmic lines of B. rapa and D. muralis. We detected higher levels of mitochondrial gene mRNAs in alloplasmic lines of B. rapa than in D. muralis. Patterns of mitochondrial gene transcription also differed among the alloplasmic lines of B. rapa. Thus, expression of mitochondrial genes in alloplasmic lines of B. rapa differed in the leaves compared to D. muralis. Overexpression of mitochondrial genes may be the result of novel interactions between the nucleus and the mitochondria in alloplasmic lines of B. rapa. Further study is necessary to clarify how these phenomena are involved in CMS.

Brassica rapa↗

PubMed2005

Genetic analysis and conservation of the endangered Canary Island woody sow-thistle, Sonchus gandogeri (Asteraceae).

Sonchus gandogeri, a woody sow-thistle, is an endangered Canary Island endemic with only two known populations, one in the El Golfo and another in the Las Esperillas of El Hierro. Amplified fragment length polymorphism (AFLP) markers were used to assess the genetic variation within and among populations. The mean genetic diversity of two populations was estimated to be 0.380, and the El Golfo population (0.380) had higher genetic diversity than the southeastern one (0.268). The unbiased Nei's genetic identity between the two populations was 0.846. The mean genetic diversity of S. gandogeri was much higher than that of the other endangered plant species. This is perhaps due to breeding system, life form, extinction, and/or introgressive hybridization and hybrid origin of the taxon. This study also indicates that the two populations are not strongly differentiated (G(ST)=0.149). This study suggests that S. gandogeri is more likely to become extinct due to environmental or demographic forces than genetic factors, such as inbreeding depression. More strict control of introduced herbivores is necessary to protect these populations, and germplasm collection for ex situ conservation is needed.

Atlantic Islands↗

PubMed2006

Extensive Natural Hybridization Between Two Geckos, Gekko tawaensis and Gekko japonicus (Reptilia: Squamata), Throughout Their Broad Sympatric Area.

The status of natural hybridization between the two Japanese geckos, Gekko tawaensis and Gekko japonicus, was surveyed by use of 15 diagnostic allozyme loci. Of 438 specimens examined, 9 were identified as F(l), 1 was a first backcross with G. japonicus, and 15 were identified as more successive generations. Hybridizations were detected at 7 of the 15 localities interspersed throughout a broad sympatric area of the two species, forming a mosaic hybrid zone. A comparison of species-hybrid composition between 2-year samples from a single locality and a 5-year interval showed no evidence for progressive introgression or establishment of a hybrid swarm, despite constant emergences of F(l) hybrids. Nonprevalence of the hybrid genotypes was also indicated by the analysis using hybrid index scores for all other localities examined. These results suggest that strong selection acts against hybrid genotypes. Morphological features of hybrid individuals were also provided.

Alleles↗

PubMed2007

Phylogenetic analysis of AA-genome Oryza species (Poaceae) based on chloroplast, mitochondrial, and nuclear DNA sequences.

Species in the genus Oryza (Poaceae) contain 10 genomic types and are distributed in pan-tropics of the world. To explore phylogenetic relationships of Oryza species having the AA-genome, DNA sequences of the chloroplast trnL intron and trnL-trnF spacer, mitochondrial nad1 intron 2, and nuclear internal transcribed spacer were analyzed, based on materials from 6 cultivated (O. sativa and O. glaberrima) and 13 wild accessions, in addition to a CC-genome species (O. officinalis) that was used as an outgroup. Analyses of the combined sequence data set from different sources provide a much better resolution of the AA-genome species than the individual data set, indicating the limitation of a single gene in phylogenetic reconstruction. The phylogeny based on the combined data set demonstrated an apparent grouping of the AA-genome Oryza species that was well associated with their geographic origin, although the Australian O. meridionalis showed its affinity with the African species. The geographic pattern of the phylogenetic relationship was probably attributed to the frequent genetic exchange and introgression among the AA-genome species from the same continents. In addition, Asian cultivated rice O. sativa showed its close relation to O. rufipogon and O. nivara, whereas African cultivated rice O. glaberrima was closely linked to O. barthii and O. longistaminata, indicating the independent domestication of the two cultivated species in different geographic locations.

Cell Nucleus↗