Chloroplast DNA inheritance in theStellaria longipes complex (Caryophyllaceae)

Inheritance of chloroplast DNA (cpDNA) was examined in F₁ progenies derived from three crosses and three corresponding reciprocal crosses betweenStellaria porsildii andS. longifolia. Chloroplast DNA restriction fragments were analyzed using methods of nonradioactive digoxigenin-11-dUTP labeling and chemiluminescent detection with Lumi-Phos 530. Distinct interspecific restriction fragment polymorphisms were identified and used to demonstrate the mode of cpDNA inheritance. Mode of cpDNA inheritance differed among crosses. Two crosses in whichS. porsildii, SP2920-21, was the maternal parent exhibited three different types of plastids, maternal, paternal and biparental, among the F₁ hybrids, suggesting a biparental cpDNA inheritance and plastid sorting-out inStellaria.     

Thinopyrum distichum chromosome morphology and C-band distribution

Thinopyrum distichum is indigenous to the southern and south western coastal shores of South Africa. Like many of the Thinopyrum species it can be hybridized with wheat. The resulting progeny treated with colchicine produce fertile amphiploids. The need to distinguish the Th. Distichum chromosomes from one another and from those of wheat prompted the investigation of the C-band distribution. The chromosome pairs of Th. distichum were distiguishable from each other and from those of wheat using C-band patterns, morphology and size as identification criteria. The chromosomes ranged from heterobrachial to metacentric with interstitial and telomeric C-bands. The C-band patterns of Th. distichum were similar, but not identical, to those of other Thinopyrum species.     

Interpretation of randomly amplified polymorphic DNA marker data for fingerprinting sweet potato (Ipomoea batatas L.) genotypes

In this paper we present a method for the generation of randomly amplified polymorphic DNA (RAPD) markers for sweet potato. These were applied to produce genetic fingerprints of six clonal cultivars and to estimate genetic distances between these cultivars. The level of polymorphism within the species was extremely high. From the 36-decamer random primers used, 170 fragments were amplified, of which 132 (77.6%) were polymorphic. Ten primers resulted in no detected amplification. Of the remaining 26 primers for which amplification was achieved, only one did not reveal polymorphism. Six primers used alone enabled the discrimination of all six genotypes. Pattern analysis, which employed both a classification and ordination method, enabled the grouping of cultivars and the identification of primers which gave greatest discrimination among the cultivars.     

Genetic analysis of morphological variation in Brassica oleracea using molecular markers

A cross between the open-pollinated Brassica oleracea cabbage cultivar Wisconsin Golden Acre and the hybrid broccoli cultivar Packman was used with molecular markers to investigate the genetic control of morphological variation. Twenty-two traits derived from leaf, stem, and flowering measurements were analyzed in 90 F₂ individuals that were also classified for genotype by restriction fragment length polymorphism (RFLP) markers. Seventy-two RFLP loci, which covered the mapped genome at an average of 10 map-unit intervals on all nine linkage groups, were tested individually for associations to phenotypic measurements by single factor ANOVA, and markers with significant associations (P<0.05) were used to develop multilocus models. These data were utilized to describe the location, parental contribution of alleles, magnitude of effect, and the gene action of trait loci. Single marker loci that were significantly associated (P<0.05) with trait measurements accounted for 6.7–42.7% of the phenotypic variation. Multilocus models described as much as 60.1% of the phenotypic variation for a given trait. In some cases, different related traits had common marker-locus associations with similar gene action and genotypic class ranking. The numbers, action, and linkages, of genes controlling traits estimated with marker loci in this population corresponded to estimates based on classical genetic methods from other studies using similar, or similarly-wide, crosses. There was no evidence that genome duplication accounted for a significant portion of multiple genes controlling trait loci over the entire genome, but possible duplications of trait loci were identified for two regions with linked, duplicated marker loci.     

RFLP tagging of a new semidwarfing gene in rice

A new rice semidwarfing gene which is not allelic tosd1, temporarily designated assdg, might be of use as a new source of semidwarfism in rice breeding programs. We report here the identification of a DNA marker closely linked to this gene. The DNA marker was identified by testing 120 mapped rice RFLP makers as hybridization probes for Southern analysis of a pair of nearly isogenic lines with or withoutsdg. Linkage association of the marker with the gene was verified using a F₂ population segregating for semidwarfism. RFLP analysis showed thatsdg is closely linked to a single-copy DNA clone RZ182 on chromosome 5, with a distance of 4.3 centiMorgans between them. This marker may facilitate early selection for the semidwarfing gene in rice breeding programs     

A population analysis of Robertsonian and Ag-NOR polymorphisms in brown trout (Salmo trutta)

An analysis of Robertsonian polymorphism and variation in the number of active NORs has been carried out in several populations of brown trout (Salmo trutta) from Northwestern Spain. The karyotype of this species appears to be soundly established, and essentially no variation has been found in chromosome number. Interindividual and interpopulation variation in arm number was detected, with figures ranging between 100 and 102 among individuals, and between 100.10 and 100.80 among populations. This variation in arm number is solely attributable to the polymorphism of the short arm of the main NOR-bearing pair 11, which can appear from acrocentric to metacentric in different individuals. Most populations analyzed showed the standard distribution of active NORs previously observed in this species. The Miño drainage basin, and specially the Chamoso population, showed a multi-chromosomal distribution of active NORs, with several new locations, always telomeric. In most cases no concordance was observed between previously detected rDNA sites in S. trutta and the new Ag-NOR locations. This fact suggests a transposition mechanism rather than an activation of silent rDNA sites to explain this multichromosomal NOR pattern.     

Growth hormone and insulin-like growth factor I concentrations in bulls of various growth hormone genotypes

A leucine/valine substitution at amino acid position 127 was identified by the polymerase chain reaction and restriction fragment length polymorphism in the bovine growth hormone gene. Genotyping was performed in 84 AI bulls of three different breeds, in which plasma concentrations of growth hormone (GH) and insulin-like growth factor I (IGF-1) were also measured. Gene frequencies of variants L (leucine) und V (valine) were 0.80/0.20 (Black and White), 0.90/0.10 (Brown), 0.71/0.29 (Simmental). Hormone concentrations were measured during different physiological conditions (normal feeding, fasting, realimentation) in the majority of animals. Generally, genotype LL was associated with higher concentrations of GH than LV. This difference was significant in Black and White bulls (P < 0.05). In contrast, IGF-1 concentrations were higher in LV than in LL animals. This was most pronounced in mature, realimented Simmental bulls. We conclude that the various GH alleles influence the circulating concentrations of GH and IGF-1.     

Selection by wild birds on artificial dimorphic prey on varied backgrounds

Our aim was to test the effects of prey frequency and background composition on selection by free-ranging birds. We did three series of experiments with populations of grey and orange pastry prey scattered among coloured stones that made the prey either conspicuous or inconspicuous. Series 1 tested whether the predicted equilibrium frequency of the two prey types was influenced by the frequency of matching grey and orange stones. Birds at a single site were given a random sequence of combinations of prey frequency and stone frequency. Selection was dependent on background and the effect of prey frequency also varied with background. In series 2, we explored the frequency-independent effect of background: birds at five sites were given equal numbers of the two prey in three frequencies of matching stones and two of non-matching. There was a higher risk of predation for prey that matched rarer stones. In series 3 we attempted to measure, at a single site, the actual equilibrium prey frequencies in three different backgrounds: two extreme stone frequencies and one intermediate. Each experiment started with a population of equal numbers of grey and orange prey. After half the prey had been eaten we calculated the frequencies of the survivors and presented a new population of the original size but with the new prey frequencies; each experiment ran for 25 such 'generations'. The results suggested that at equilibrium the commoner 'morph' was the one that resembled the commoner colour of stone. Overall, our findings support the idea that visual selection can result in morph frequencies becoming related to the proportions of their matching background components and that this equilibrium will 'track' temporal or spatial changes in the background.     

HIV-1 integrase blocks infection of bacteria by single-stranded DNA and RNA bacteriophages

Expression of human immunodeficiency virus-1 integrase in Escherichia coli, at levels that had no effect on bacterial cell growth, blocked plaque formation by bacteriophages having single-stranded genomic DNA (M13) or RNA (R17, Q, PRR1). Plaque formation by phages having double-stranded genomic DNA (T4, PR4) was unaffected. Integrase also inhibited infection by the phagemid M13KO7, but it had no effect on production of phage once infection by M13KO7 was established. This result indicated that integrase affects an early stage in infection. Integrase also inhibited phage production following transfection by either single-stranded or double-stranded (replicative form) M13 DNA, it blocked M13 DNA replication, as assayed by incorporation of radioactive nucleotides into DNA, and it failed to affect bacterial pilus function. These data suggest that integrase interacts in vivo with phage nucleic acid, a conclusion supported by studies in which integrase was shown to have a DNA-binding activity in its C-terminal portion. This portion of integrase was both necessary and sufficient for interference of plaque formation by M13 in the present study. Expression of the N-terminal portion of integrase at the same level as intact integrase had little effect on phage growth, indicating that expression of foreign protein in general was not responsible for the inhibitory effect. The simple bacteriophage assay described is potentially useful for identifying integrase mutants that lack single-stranded DNA binding activity.     

A 70-amino acid zinc-binding polypeptide fragment from the regulatory chain of aspartate transcarbamoylase causes marked changes in the kinetic mechanism of the catalytic trimer.

Interaction between a 70-amino acid and zinc-binding polypeptide from the regulatory chain and the catalytic (C) trimer of aspartate transcarbamoylase (ATCase) leads to dramatic changes in enzyme activity and affinity for active site ligands. The hypothesis that the complex between a C trimer and 3 polypeptide fragments (zinc domain) is an analog of R state ATCase has been examined by steady-state kinetics, heavy-atom isotope effects, and isotope trapping experiments. Inhibition by the bisubstrate ligand, N-(phosphonacetyl)-L-aspartate (PALA), or the substrate analog, succinate, at varying concentrations of substrates, aspartate, or carbamoyl phosphate indicated a compulsory ordered kinetic mechanism with carbamoyl phosphate binding prior to aspartate. In contrast, inhibition studies on C trimer were consistent with a preferred order mechanism. Similarly, 13C kinetic isotope effects in carbamoyl phosphate at infinite aspartate indicated a partially random kinetic mechanism for C trimer, whereas results for the complex of C trimer and zinc domain were consistent with a compulsory ordered mechanism of substrate binding. The dependence of isotope effect on aspartate concentration observed for the Zn domain-C trimer complex was similar to that obtained earlier for intact ATCase. Isotope trapping experiments showed that the compulsory ordered mechanism for the complex was attributable to increased "stickiness" of carbamoyl phosphate to the Zn domain-C trimer complex as compared to C trimer alone. The rate of dissociation of carbamoyl phosphate from the Zn domain-C trimer complex was about 10(-2) that from C trimer.(ABSTRACT TRUNCATED AT 250 WORDS)