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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Molecular genetics and genomics 108 (1970), S. 225-232 
    ISSN: 1617-4623
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Reversion at the gl 1 locus in maize has been studied by using crosses between 10 gl 1 mutants of independent origin and an o 2 gl st sl stock. The observed reversion frequencies have been explained on the basis of intragenic recombination. These frequencies make it possible to detect in the gl 1 cistron the existence of different positions where mutational events take place. The finding of a high number of reversions with parental outside markers can be explained by genetic mechanisms different from classical crossing-over, but comparable to those known in microorganisms as “high negative interference”.
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  • 2
    ISSN: 1617-4623
    Keywords: Potato transformation ; Ac transposition ; Gene tagging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The maize transposable element Ac has been introduced into potato via the T-DNA (transferred DNA) of Agrobacterium tumefaciens. Ac was inserted within the untranslated leader region of a neomycin phosphotransferase II (NPT-II) gene such that excision restored NPT-II activity. Two approaches to monitor Ac excision were used. (i) Using an Agrobacterium strain harbouring plasmid pGV3850::pKU3, leaf discs were selected on kanamycin (Km) after exposure to Agrobacterium. (ii) Using a strain containing plasmid pGV3850HPT::pKU3, the leaf discs were selected on hygromycin (Hm) and the resulting shoots were checked for NPT-II expression. Thirteen kanamycin resistant shoots transformed with pGV3850::pKU3 were isolated, suggesting that Ac had excised from the NPT-II gene. Out of 43 hygromycin resistant shoots transformed with pGV3850HPT::pKU3, 22 expressed the NPT-II gene, indicating that Ac had undergone excision in approximately 50% of the hygromycin resistant shoots. Southern analysis revealed that all kanamycin resistant plants contained the DNA restriction fragments expected when Ac excises from the NPT-II gene. The presence of Ac at new locations within the genomic DNA of several transformants was also detected.
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  • 3
    ISSN: 1617-4623
    Keywords: Self-incompatibility ; Solanum ; S locus ; Molecular recognition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Allelic complexity is a key feature of self-incompatibility (S) loci in gametophytic plants. We describe in this report the allelic diversity and gene structure of the S locus in Solanum tuberosum revealed by the isolation and characterization of genomic and cDNA clones encoding S-associated major pistil proteins from three alleles (S 1, S r1, S 2). Genomic clones encoding the S1 and S2 proteins provide evidence for a simple gene structure: Two exons are separated by a small intron of 113 (S 1) and 117 by (S 2). Protein sequences deduced from cDNA clones encoding S1 and Sr1 proteins show 95% homology. 15 of the 25 residues that differ between these S 1and S r1alleles are clustered in a short hypervariable protein segment (amino acid positions 44–68), which corresponds in the genomic clones to DNA sequences flanking the single intron. In contrast, these alleles are only 66% homologous to the S 2allele, with the residues that differ between the alleles being scattered throughout the sequence. DNA crosshybridization experiments identify a minimum of three classes of potato S alleles: one class contains the alleles S 1, S r1and S 3, the second class S 2and an allele of the cultivar Roxy, and the third class contains at present only S 4. It is proposed that these classes reflect the origin of the S alleles from a few ancestral S sequence types.
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  • 4
    ISSN: 1617-4623
    Keywords: Potato virus X ; Resistance genes ; RFLP ; Solanum tuberosum ; Genetic introgression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Two different chromosomal locations of major genes controlling extreme resistance to potato virus X (PVX) were found by restriction fragment length polymorphism (RFLP) analysis of two populations segregating for the resistance. The resistance geneRx1 mapped to the distal end of chromosome XII, whereasRx2 was located at an intermediate position on linkage group V in a region where reduced recombination and segregation distortion have also been observed. These linkage anomalies were due to abnormal behaviour of the chromosome contributed by the resistant parent P34. The results presented were obtained using two different strategies for mapping genes of unknown location. One approach was the use of probes revealing polymorphic loci spread throughout the genome and resulted in the mapping ofRx1. The second approach was based on the assumption of possible linkage between the resistance gene and clone-specific DNA fragments introduced from a wild potato species.Rx2 was mapped by adopting this strategy.
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  • 5
    ISSN: 1617-4623
    Keywords: Potato ; Phytophthora infestans ; Resistance ; Restriction fragment length polymorphism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Late blight in potato is caused by the fungusPhytophthora infestans and can inflict severe damage on the potato crop. Resistance toP. infestans is either based on major dominantR genes conferring vertical, race-specific resistance or on “minor” genes inducing horizontal, unspecific resistance. A dihaploid potato line was identified which carried theR1 gene, conferring vertical resistance to allP. infestans races, with the exception of those homozygous for the recessive virulence allele of the locusV1. The F1 progeny of a cross between this resistant parent P(R1) and P(r), a line susceptible to all races, was analysed for segregation ofR1 and of restriction fragment length polymorphism (RFLP) markers distributed on the potato RFLP map comprising more than 300 loci. TheR1 locus was mapped to chromosome V in the interval between RFLP markers GP21 and GP179. The map position ofR1 was found to be very similar to the one ofRx2, a dominant locus inducing extreme resistance to potato virus X.
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  • 6
    ISSN: 1617-4623
    Keywords: Key words Endosperm ; Opaque-2 locus ; General control ; Amino acid biosynthesis ; Carbon partitioning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The maize Opaque-2 (O2) protein is a transcription factor of the basic/leucine-zipper class, involved in the regulation of endosperm proteins including the 22 kDa α-zein storage proteins and b32 protein. In this study we have focussed our attention on the relationship between O2 and the cyPPDK1gene, which encodes a cytoplasmic pyruvate orthophosphate dikinase (PPDK) isoform. The results of this study showed that PPDK activity is detectable in wild-type maize endosperms, while in o2 mutant endosperms, the levels of PPDK protein, mRNA, and enzymatic activity are reduced, indicating that O2 is involved in the regulation of cyPPDK1 in this tissue. By employing transient expression experiments in tobacco mesophyll protoplasts, we have demonstrated that the O2 protein can activate expression of a chloramphenicol acetyl transferase reporter gene placed under the control of the cyPPDK1 promoter. An in vitro binding assay and DNaseI footprint analysis demonstrated that a specific sequence in the cyPPDK1 promoter can be recognized and protected by maize O2 protein. The regulation by the O2 locus of cyPPDK1 reported here, and control of α-zein synthesis by O2 suggest that the O2 protein may play a more general role in maize endosperm development than previously thought.
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  • 7
    ISSN: 1617-4623
    Keywords: Key words Opaque-2 ; 22 kD α-zeins ; Endosperm ; Transient gene expression ; Particle bombardment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Opaque-2 (O2) encodes a transcriptional activator of the basic domain-leucine zipper (bZIP) class, which controls the expression level in maize endosperm of the 22 kD α-zeins and a number of non-storage proteins. The interaction of the O2 protein at three clustered binding sites on an isolated 22 kD zein gene promoter has been investigated. O2 is shown to transactivate transcription from these sites in tobacco mesophyll protoplasts as well as in maize endosperm cells transformed by particle bombardment. The binding sites have been mutated by base exchanges, singly or in different combinations, to determine their contribution to transactivation in vivo in both the leaf protoplast and the maize endosperm system. The effect of these mutations on binding of O2 in vitro was determined by electrophoretic mobility shift assays (EMSA), using O2 protein expressed in E. coli. Two of the sites seemed to be equally effective in responding to Opaque-2 in vivo in both cell types, although one of them does not contain an ACGT core sequence, and has a lower affinity for O2 in vitro than the ACGT-containing binding site. A third site, which has the lowest affinity of all three, confers no detectable O2-dependent promoter activation alone, but significantly increases activation in combination with either one of the other sites. Hence, weaker O2 binding sites can still mediate major O2-dependent effects when present in target promoters in vivo.
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  • 8
    ISSN: 1617-4623
    Keywords: Barley ; RFLP markers ; AFLP markers Genome mapping ; Genome mapping
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract AFLP marker technology allows efficient DNA fingerprinting and the analysis of large numbers of polymorphic restriction fragments on polyacrylamide gels. Using the doubled haploids from the F1 of the cross Proctor × Nudinka, 118 AFLP markers were mapped onto a barley (Hordeum vulgare L.) RFLP map, also including five microsatellite and four protein marker loci. The AFLP markers mapped to all parts of the barley chromosomes and filled in the gaps on barley chromosomes 2L, 4L and 6 in which no RFLP loci had been mapped. Interestingly, the AFLP markers seldom interrupted RFLP clusters, but grouped next to them. The combined map covers 1873 cM, with a total of 282 markers. The merging of AFLP and RFLP markers increased the total map length; 402 cM were added to the map at the tips of chromosomes or in regions corresponding to earlier gaps. Another 375 cM resulted from mapping AFLP markers near to RFLP clusters or in between non-clustered RFLP markers.
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  • 9
    ISSN: 1617-4623
    Keywords: Potato ; Phytophthora infestans ; Resistance ; Map-based cloning ; AFLP markers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The R1 allele confers on potato a race-specific resistance to Phytophthora infestans. The corresponding genetic locus maps on chromosome V in a region in which several other resistance genes are also located. As part of a strategy for cloning R1, a high-resolution genetic map was constructed for the segment of chromosome V that is bordered by the RFLP loci GP21 and GP179 and includes the R1 locus. Bulked segregant analysis and markers based on amplified fragment length polymorphisms (AFLP markers) were used to select molecular markers closely linked to R1. Twenty-nine of approximately 3200 informative AFLP loci displayed linkage to the R1 locus. Based on the genotypic analysis of 461 gametes, eight loci mapped within the GP21–GP179 interval. Two of those could not be seperated from R1 by recombination. For genotyping large numbers of plants with respect to the flanking markers GP21 and GP179 PCR based assays were also developed which allowed marker-assisted selection of plants with genotypes Rr and rr and of recombinant plants.
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  • 10
    ISSN: 1617-4623
    Keywords: Potato ; Solanum tuberosum ; Nematode resistance ; Map-based cloning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The dominant allele Gro1 confers on potato resistance to the root cyst nematode Globodera rostochiensis. The Gro1 locus has been mapped to chromosome VII on the genetic map of potato, using RFLP markers. This makes possible the cloning of Gro1 based on its map position. As part of this strategy we have constructed a high-resolution genetic map of the chromosome segment surrounding Gro1, based on RFLP, RAPD and AFLP markers. RAPD and RFLP markers closely linked to Gro1 were selected by bulked segregant analysis and mapped relative to the Gro1 locus in a segregating population of 1105 plants. Three RFLP and one RAPD marker were found to be inseparable from the Gro1 locus. Two AFLP markers were identified that flanked Gro1 at genetic distances of 0.6 cM and 0.8 cM, respectively. A genetic distance of 1 cM in the Gro1 region corresponds to a physical distance of ca. 100 kb as estimated by long-range restriction analysis. Marker-assisted selection for nematode resistance was accomplished in the course of constructing the high-resolution map. Plants carrying the resistance allele Gro1 could be distinguished from susceptible plants by marker assays based on the polymerase chain reaction (PCR).
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