Pgd Locus Research Articles

Morphologically Intermediate form betweenAthous haemorrhoidalisandA. vittatus(Coleoptera: Elateridae): A Case of Hybridization? a Preliminary Study

In the present preliminary study we report an investigation on taxonomic status of individuals displaying diagnostic traits of intermediate values between the morphologically typical forms of Athous haemorrhoidalis (Fabricius 1801) and A. vittatus (Gmelin 1790) species occurring sympatrically. The presence of the “intermediate form” invoked the hypothesis of interspecific hybridization between A. haemorrhoidalis and A. vittatus species. An alternative explanation is that the “intermediate form” comprises individuals that are morphological variants of either of the species, without interspecific gene flow. We used partial sequences of two mitochondrial genes coding for the cytochrome oxidase subunit I (cox1) and 16S ribosomal RNA (rrnL), respectively. Additionally, we examined the variability of five polymorphic allozyme loci: 6Pgd, Idh, Mdh, Pgm and Gpi. Altogether, 28 A. haemorrhoidalis, 7 A. vittatus and 8 “intermediate form” individuals were included into the study. Phylogenetic analyses produced the trees of a consistent topology with high statistical support regardless of the method used. The specimens signified as the “intermediate form” constituted a monophyletic group with individuals of A. vittatus species. Empirical data confirmed that the reproductive isolation between the species studied is complete. No haplotype was shared between A. haemorrhoidalis and A. vittatus in sympatry. Similar results were obtained using the analysis of allozyme data. Especially at Idh and 6Pgd loci, alleles characteristic for A. vittatus and the “intermediate form” were not found in A. haemorrhoidalis, despite the larger sample examined. This suggests that the “intermediate form” is a phenotypic variant of A. vittatus without the signature of introgression.

Genetic Structure and Variation of Van Cats

To determine the genetic structure and variation of Van cats and some other cats, seven enzyme loci were examined using horizontal starch gel electrophoresis. ME bands were observed for the first time in cats. For the enzyme loci CA ( 1 ), SOD, GPI, and GOT, neither the individual Van cats nor the specimens of other cat species exhibited any variation. These enzymes presented identical bands, all of which were homozygous. With respect to the PGD, ME, and ESD loci, however, genetic variation was observed in all of the cats. Hence, three of the seven gene-enzyme systems (43%) were polymorphic with two alleles, contributing to an estimate of average heterozygosity of 0.33-0.49 for the Van cats. PGD was the most discriminatory among the three polymorphic loci. The phylogenetic tree indicated that the Van, Persian, Turkish Angora, and Turkish Tekir cats are distinct from Siamese and Bombay cats.

Interpopulation Crosses, Inheritance Study, and Genetic Variability in the Brown Planthopper Complex, Nilaparvata lugens (Homoptera: Delphacidae)

Studies on hybridization, inheritance, and population genetics of brown planthoppers that infest rice and weeds were undertaken using starch gel electrophoresis to determine whether the weed-infesting population represents a biological race or a species. F(1) and F(2) generations were produced by crosses between parental insects from the two populations with little indication of hybrid sterility. Gpi, Mdh, and Idh loci were inherited in a simple Mendelian fashion in families of two sympatric populations. Sixteen populations of Nilaparvata spp. from eight locations were collected. The Mdh, Idh, Pgm, Gpi, 6Pgd, and Acp loci were polymorphic. The N. lugens of rice with high esterase activity were clustered into a group and characterized by the presence of alleles Gpi (110) and Gpi (120), whereas N. lugens from weeds with low esterase activity were clustered into another group and characterized by Gpi (100) and Gpi (90) . There was a lack of heterozygotes between the common alleles of the two populations. This means that the two groups of individuals belong to different gene pools.

Absence of genetic linkage between A1BG, PGD and HPX loci in rabbits

Linkage relationships between A1BG, PGD, and HPX loci of rabbits were studied on segregation data in backcross matings. No sign of linkage between the three studied loci was found.

Selection at 6-PGD locus in laboratory populations ofBactrocera oleae

We have previously shown that laboratory populations of the olive fruitfly Bactrocera oleae come to equilibrium with allele frequencies at the 6-phosphogluconate dehydrogenase (6-PGD) locus markedly different from those of wild populations. In this study, we present new evidence from perturbation experiments in support of the notion that the locus is under selective pressure under laboratory conditions. Eleven populations were started with frequencies at the 6-PGD locus different from the laboratory equilibrium. Over 12 generations, the populations showed a return to the previous equilibrium, indicating a direct and powerful selection pressure on the naturally occurring allozymes of this locus. That is, a marked increase of the F allele followed by a compensatory decrease of allele I. Populations were set up to minimize the effects of associative overdominance, and we discuss the possible influence of this factor. Nucleotide sequence for the 6-PGD F and I alleles revealed two missense mutations at positions 501 and 730 leading to different amino acids among the two alleles.

Position-effect variegation in Drosophila melanogaster X chromosome inversion with a breakpoint in a satellite block and its suppression in a secondary rearrangement.

In(1LR)pn2a is a pericentric inversion with a euchromatic breakpoint in the 2E polytene region and a heterochromatic breakpoint in the right arm of the X chromosome. It is associated with position-effect variegation (PEV) of the pn, wapl, Pgd and other vital loci of the 2E region, which are relocated near the bulk of the X heterochromatin. Cytological analysis showed that the rearrangement brings the 1A-2E euchromatic segment directly into contact with a major portion of the h34 block, a heterochromatic region that is positively stained by the N-banding technique and contains the AAGAG satellite sequences. Molecular cloning revealed the presence of a new junction between euchromatin and AAGAG satellite sequences and demonstrated that the euchromatic breakpoint of In(1LR)pn2a lies in the vinculin gene. In the X ray-induced secondary rearrangement In(1LR)r30, consisting of a pericentric inversion superimposed on In(1LR)pn2a, the h34 material remains associated with the 2E region but is separated from the rest of the X heterochromatin. In this case, the pn, wapl and Pgd loci no longer variegate, suggesting that the satellite-containing h34 region is not able per se to induce detectable PEV on the adjacent euchromatic genes.

Glucose utilization by 6pgd genotypes in Lolium perenne

To gain a deeper understanding of the mechanisms underlying associations between allozyme genotypes and rates of respiration in Lolium perenne, Vmax Km and rates of glucose flux through glycolysis and the pentose phosphate pathway were estimated for the three genotypes of the 6pgd locus. Km Vmax and Vmax/Km differed significantly among genotypes. Values of Km for the 11, 12, and 22 genotypes were 0.29, 0.25, 0.13, while the values of Vmax/Km for die 11, 12, and 22 genotypes were 3.79, 3.85, 6.70. Flux through the pentose shunt did not differ among genotypes at 20 °C, but at 35 °C the rates of flux for the 11, 12, and 22 genotypes were 0.15, 0.25 and 0.42, respectively. Thus, the 6PGD allozyme genotypes differ markedly in both enzyme kinetic characteristics and in flux through a metabolic pathway. These associations reveal potentially causal relationships between allozyme genotypes and rates of respiration.

Single-strand conformation polymorphism analysis coupled with stratified DNA sequencing reveals reduced sequence variation in the su(s) and su(wa) regions of the Drosophila melanogaster X chromosome.

Single-strand conformation polymorphism (SSCP) analysis followed by DNA sequencing of stratified sub-samples was used to survey DNA polymorphism in the su(s) and su(wa) regions in a natural population of Drosophila melanogaster. su(s) and su(wa) are located near the telomere of the X chromosome, where the rate of crossing over per kilobase of DNA monotonically decreases toward the tip. SSCP was assessed in 12 noncoding segments amplified from the su(s) region (3213 bp) and in 8 noncoding segments amplified from the su(wa) region (1955 bp). Sets of segments were multiplexed in a single electrophoretic lane to increase the number of base pairs assayed per lane. Eight segments were monomorphic, and the other 12 segments exhibited two to four SSCP classes. Only four within-SSCP-class DNA sequence differences (a single nucleotide substitution) were observed among 24,360 bp compared within classes. The between-SSCP-class DNA sequence comparisons revealed 27 substitutions and 9 insertion/deletion polymorphisms. The average numbers of substitutional differences per site were 0.0010 and 0.0021 for su(s) and su(wa), respectively. These values are intermediate between those reported for the more distal y-ASC region (0.0004) and the more proximal Pgd locus (0.0024). This observation is consistent with the prediction of the hitchhiking-effect model-i.e., a monotonic increase in polymorphism as a function of crossing over per kilobase.

Detection of the ryanodine receptor mutation associated with malignant hyperthermia in purebred swine populations1

A restriction endonuclease assay (REA) that reveals a C/T transition in the ryanodine receptor gene (ryr-1 locus) was proposed to test swine for malignant hyperthermia. The REA was tested in a heterologous pig population of 1,227 individuals representing Hampshire, Duroc, Landrace, and Yorkshire breeds. Of this group, 713 pigs had been classified on the basis of the halothane challenge and progeny testing into the three possible Hal genotypes (685 negatives, 24 carriers, and 4 susceptibles). The REA confirmed the four susceptibles as T/T, 17/24 carriers as C/T, and 659/685 negatives as C/C. The rest of the sample was constituted of 514 pigs that had not been selected on the basis of the halothane gene. The proportions of C/T and T/T pigs within the breeds represented were 3.2 and 1.6% for Duroc, 27.3 and 1.4% for Landrace, and 17.9 and 1.9% for Yorkshire. No T/T allelic pairs were found in the Hampshire breed, although the sample was very small. Genotypic distribution and allelic frequencies at the ryr-1, Phi, and Pgd loci were reported among the breeds.

Direct measurement of in vivo flux differences between electrophoretic variants of G6PD from Drosophila melanogaster.

Demonstrating that naturally occurring enzyme polymorphisms significantly impact metabolic pathway flux is a fundamental step in examining the possible adaptive significance of such polymorphisms. In earlier studies of the glucose-6-phosphate dehydrogenase (G6PD) polymorphism in Drosophila melanogaster, we used two different methods, exploiting both genotype-dependent interactions with the 6Pgd locus, and conventional steady-state kinetics to examine activity differences between the two common allozymes. In this report we use 1-14C- and 6-14C-labeled glucose to estimate directly genotype-dependent flux differences through the pentose shunt. Our results show that G6pdA genotype possesses statistically lower pentose shunt flux than G6pdB at 25 degrees. We estimate this to be about a 32% reduction, which is consistent with the two former studies. These results reflect a significant responsiveness of pentose shunt flux to activity variation at the G6PD-catalyzed step, and predict that the G6PD allozymes generate a polymorphism for pentose shunt flux.

Expression and distribution of cytosolic 6-phosphogluconate dehydrogenase isozymes in maize.

Maize (Zea mays L.) cytosolic 6-phosphogluconate dehydrogenase isozymes (EC 1.1.1.44; 6-PGD) are encoded by unlinked loci Pgd1 and Pgd2. Two families from a Robertson's Mutator line were isolated which have no detectable expression of Pgd2. These Pgd2-null mutants and a Pgd1-null line were used to generate plants homozygous for null alleles at both cytosolic 6-PGD loci. The specific activity of 6-PGD in the double-null mutant was between 20 and 30% of wild-type levels in root extracts. The double-null mutant was reproductively viable in a moderate environment, suggesting that wild-type levels of cytosolic 6-PGD activity are not essential for growth. Isozyme dimer ratios in roots, leaves, and scutellum were binomial and reflected the wild-type gene copy number. 6-PGD isozymes showed tissue- and cell type-specific expression.

Genetic and linkage analysis of isozyme loci in Daucus carota L.

Electrophoretic polymorphisms of eight enzyme systems were studied in leaves of Daucus carota ssp. sativus in order to identify additional isozyme loci and generate first linkage groups of genetic markers. The genetic analysis of aconitase (ACO), leucin aminopeptidase (LAP), menadione reductase (MDR), phosphoglucomutase (PGM), 6-phosphogluconic dehydrogenase (6-PGD), shikimate dehydrogenase (SKD), and triose phosphate isomerase (TPI) zymograms resulted in the identification of 8 isozyme marker loci, designated as Aco-1, Lap-1, Pgm-1, Pgm-3, 6-Pgd-2, Skd-1, Tpi-1, and Tpi-2. All loci segregated with codominant alleles and encoded for monomers (ACO, LAP, PGM, SKD), and dimers (6-PGD, TPI), respectively. MDR enzymes of the variable region MDR-2 appeared to be identical with Dia-2 isozymes. Tests of joint segregation for pairwise comparisons of all 14 isozyme marker loci now available in carrots indicate that 12 loci are linked in 4 linkage groups (marked K1 to K4) in the following order: Aco-1, Pgi-1, and Dia-3 (K1), Tpi-2, Got-2, and Lap-1 (K2), Got-3 and Tpi-1 (K3) and Pgm-1, Pgm-3, 6-Pgd-2 and Skd-1 (K4). Dia-2 and Got-1 remained unlinked. The possible duplication of a PGM locus and a 6-PGD locus is discussed.

Localization of the PGD and TGFβ‐1 loci to pig chromosome 6q

The TGF beta-1 and PGD loci have been localized by in situ hybridization to the C-greater than q2.1 and q2.2 -greater than q2.5 regions of pig chromosome 6. These assignments confirm that the conversation of syntenic groups around GPI and PGD extends to pigs where these two groups are uniquely found to be linked. Our data also support the hypothesis that the porcine and human inherited malignant hyperthermia syndromes are caused by mutations in homologous genes which map to human chromosome 19q, porcine chromosome 6q and murine chromosome 7.

Lack of association between allozymic variation and social dominance in free-living White-throated Sparrows

This study examined possible associations between allozymic variation in metabolic enzymes and social dominance or survival in a large free-living population of wintering White-throated Sparrows (Zonotrichia albicollis). Electrophoresis of 15 enzymes resolved from muscle biopsies from 173 sparrows revealed nine enzymes with some variation. Two of these (PGM and 6-PGD) showed substantial variation, with the frequency of the common allele below 0.9. During two seasons dominance interactions among the biopsied birds were observed at three feeding stations. There was no association between social dominance (percentage of opponents dominated) and genotype at the two most variable loci or overall proportion of heterozygotes at either the two most variable loci or the seven most consistently scored loci. Older birds were more likely than expected to be heterozygous at both the PGM and 6-PGD loci, but heterozygotes did not return more frequently than homozygotes in subsequent years. Although we cannot exclude a weak association of dominance and isozyme variability, we can conclude that social dominance during winter lacks any strong relationship with variation at loci for metabolic enzymes.

Migration and linkage disequilibrium in local populations of the housefly (Musca domestica) in Japan.

Housefly populations in Hokkaido, Japan were examined. The frequency of females carrying a female-determining factor (F), which is epistatic to the male-determining factor (M), has been estimated to be very low. This means that most of the chromosomes carrying an M factor are transferred from male parents to their male progeny without recombination. Based on this characteristic situation, the association between theMfactor and one of the 6PGD alleles in Hokkaido in 1983 and 1984 was studied, and strong linkage disequilibrium was found in the samples from six spots in and around Sapporo. A specific allele, 6PGD1, was associated in most of the cases with theMfactor-carrying third chromosome (IIIM). The 6PGD locus was highly polymorphic in the M factor-free third chromosome (III). Based on these experimental results, it is suggested that the frequency of chromosome IIIMhas recently increased in the population around Sapporo.

A new allele at the Pgd locus in pigs.

A new electrophoretic variant of porcine 6-phosphogluconate dehydrogenase (PGD) is described. The new variant, PGD C, has been shown to be controlled by a third allele, PgdC, at the Pgd locus.

Gene constitution of indigenous chickens in Bangladesh.

Morphological characteristics, blood groups and blood protein polymorphisms of indigenous chickens in Bangladesh were investigated. Gene frequencies were analyzed at 29 loci controlling comb shape (the P, R and Cr loci), plumage color (the B, E, I and S loci), shank color (the Id locus), blood groups (the Ea-A, Ea-B, Ea-D and Ea-E loci) and blood proteins (the Amy-1 and -3, Akp and Akp-2, Es-1, Alb, Tf, Pas, Hb-1 and -2, LDH, 6-PGD, PGM, PHI, To, MDH and Es-D loci). In addition, phenotypic frequency of earlobe color was also examined. Among these 29 loci, 8 blood protein loci were monomorphic. Gene frequencies were compared among the local populations in Bangladesh. The frequencies of the E and I alleles for plumage color and of the Amy-1A and Hb-1A alleles for blood proteins showed a geographical cline. These frequencies were a little higher in the populations of the Chittagong Division than in those of the Dhaka Division. Although gene frequencies at other loci also varied considerably among the local populations, no geographical cline was found. Genetic distances between each pair of the local populations were small, and the coefficient of gene differentiation among them, GST, was only .058. These results suggest that the indigenous chickens (nondescript deshi type) of Bangladesh may be regarded as one breed or population.

Inheritance and linkage relationships of 6-phosphogluconate dehydrogenase isozymes in soybean

The inheritance of 6-phosphogluconate dehydrogenase (6-PGD) in dry seeds of cultivated and wild soybean was studied electrophoretically. There are four 6-PGD anodal bands that are controlled by three loci. Bands 1 and 3 are homodimers, whereas band 2 is the interlocus heterodimer of bands 1 and 3, which are products of the Pgd1 and Pgd2 loci, respectively. Both Pgd1 and Pgd2 loci have three codominant alleles (Pgd1-a, Pgd1-b, Pgd1-c and Pgd2-a, Pgd2-b, Pgd2-c) and each of the alleles specifies an isozyme band. The two variants of the fourth band are the result of two codominant alleles (Pgd3-a and Pgd3-b) of the Pgd3 locus. The Pgd3-a allele is found only in PI486.220, a Glycine soja accession from Japan. The Pgd2 is linked to Ap, Ti, and Lap1 in the order of Ap–Ti–Lap1–Pgd2 and belongs to linkage group 9. Key words: soybean isozymes linkage, genetics of Pgd loci.

Associations between enzyme genotypes and dark respiration in perennial ryegrass, Lolium perenne L.

In this study, we determined whether relationships existed between dark respiration and genotype at five enzyme polymorphisms in perennial ryegrass, Lolium perenne L. Positive correlations were found between Q 10 of dark respiration and genotype at the phosphoglucomutase (PGM) and 6-phosphogluconate dehydrogenase (6PGD) loci. Plants doubly homozygous for the common allele at these loci were found to have Q 10 values 20% higher than those for double heterozygotes. In plants that were heat stressed for five consecutive days, Q 10 was found to be negatively correlated with apparent vigor after stressing. Individuals homozygous for PGM and 6PGD (with higher Q 10 values) exhibited more apparent damage following the stress than heterozygous individuals. Both PGM and 6PGD occupy positions in metabolism with regulatory potential. Although caution must be used in assigning causal relationships, the results suggest that specific forms of these enzymes are directly related to, or are correlated with, the determinants of respiratory efficiency in L. perenne.

Localization of the Po2 locus in the S, Phi, Hal, H, Po2, Pgd linkage group in pigs

The localization of the Po2 locus controlling a polymorphic serum postalbumin was studied in 41 families of the Czech Landrace breed. The haplotypes involving six closely linked loci (S, Phi, Hal, H, Po2, Pgd) were determined for each family member. The crossovers observed between the H, Po2 and Pgd loci indicated that Po2 is located between H and Pgd. The Po2 locus appears to be closer to H [theta = 0.54% (0.06%-1.92%)] than to Pgd [theta = 4.02% (1.67%-7.96%)]. A strong Ha-Po2S association (r = 0.96, P less than 0.001) and H-PO2 linkage disequilibrium (D = 0.2218, P less than 0.01, D/DMax = 0.98) were found.