A map of barley chromosome 2 using isozymic and morphological markers

The F₂ progeny of a cross between a chromosome 2 multiple marker stock and an adapted cultivar of barley were analyzed for four morphological markers and electrophoretic patterns of eight leaf isozymes. TheIdh-2 locus was linked to thePer-5 locus (27.96±5.07 cM) and to thee locus (10.26±3.13 cM). Also, thePer-5 ande loci were located on the short arm of chromosome 2. In additionIdh-2 was also located on barley chromosome 2 and was linked to thev locus (13.18±3.56 cM), which is located on the long arm of chromosome 2. Two other marker genes,li andwst,,B, were linked (26.50±5.24 cM) on chromosome 2 but segregate independently of the other loci evaluated. This project was supported by funds from the U.S.-Spain Joint Committee for Scientific and Technological Cooperation.     

Linkage analysis of the mutation locus in the eye lens obsolescence (Elo) mouse

To map precisely the mutation locus of eye lens obsolescence (Elo) on mouse chromosome 1, subsequent linkage analysis was achieved using backcross mating between 129/SvSl-Elo (Elo/+) and 129/SvSl (+/+). Mouse genomic DNAs from 17 strains including the Elo mutant mouse were first digested with several restriction enzymes and analyzed by hybridization using gamma 2- and gamma 4-crystallin cDNAs as probes. Restriction endonuclease DraI showed distinct RFLP patterns in both cases. When gamma 2-crystallin cDNA was used as the probe, two strong bands were observed at 4.0 and 2.4 kb in the majority of strains, but the former fragment shifted to the 3.4-kb position in 129/SvSl-Elo (Elo/Elo) and CFO. The polymorphism between 4.0- and 3.4-kb fragments corresponded to the gamma 1-crystallin locus (Cryg-1), and that of the 2.4-kb one, to the gamma 2-crystallin locus (Cryg-2). Mouse DNAs were also analyzed by hybridization using gamma 4-crystallin cDNA (Cryg-4). In this case, 3.4- and 3.0-kb fragments were observed in Elo and wild-type mice, respectively. The backcross offsprings were analyzed with respect to Elo, Idh-1, Cryg-1, and Cryg-4 loci. Among 223 mice analyzed, recombination between Elo and Idh-1 loci was observed in three offsprings; and that between Cryg-1 or Cryg-4 and Idh-1 loci, in one offspring. No recombination occurred between Cryg-1 and Cryg-4 alleles.     

Linkage of faded gene (fe) to chromosome 6 of the mouse

Linkage tests on the faded gene were carried out with some coat color and biochemical markers, It was shown that the faded locus was not closely linked to the following loci: Idh-1 (chromosome 1), a (2), Car 2 (3), Mup-1 (4), Pgm-1 (5), Hbb (7), Gpi-1 (7), Es-1 (8), Trf (9), Es-3 (11), s (14), Sod-1 (16) and Ce-2 (17). The mutant locus showed linkage with Ggc on chromosome 6.     

Mapping of the bcl-2 oncogene on mouse chromosome 1

Two bcl-2 alleles have been identified in inbred strains of mice by restriction fragment length polymorphism (RFLP). Analysis of a bcl-2 RFLP in a series of bilineal congenic strains (C.D2), developed as a tool for chromosomal mapping studies, revealed linkage of bcl-2 to the Idh-1/Pep-3 region of murine chromosome 1. The co-segregation of bcl-2 alleles with allelic forms of two other chromosome 1 loci, Ren-1,2 and Spna-1, in a set of back-cross progeny, positions bcl-2 7.8 cM centromeric from Ren-1,2.     

Assignment of the human γ-crystallin gene cluster (CRYG) to the long arm of chromosome 2, region q33–36

Summary The -crystallins of the human eye lens are encoded by a multigene family of which at least six genes have recently been assigned to chromosome 2. We have now localized these genes to the distal region of the long arm of chromosome 2 (region q33-36, most probably q34-35) using somatic cell hybrids containing different parts of this chromosome and by in situ hybridization. The -crystallin genes map to the same chromosomal region as IDH-1. Similar linkage exists between the loci Len-1 and Idh-1 on mouse chromosome 1.     

Genetic differentiation and local adaptation in the salt-marsh beetle Pogonus chalceus: a comparison between allozyme and microsatellite loci

The genetic structure of Pogonus chalceus from 11 Atlantic and seven Mediterranean Western European populations was analysed. Results from seven allozyme loci were compared to five microsatellites to test the hypothesis that some enzymatic loci undergo selection. Both allozyme and microsatellite results showed that Mediterranean beetle populations are genetically distinct from Atlantic populations. The analysis of the genetic structure showed that FST values derived from all microsatellite loci were much smaller than those obtained from allozymes. The enzymatic locus Idh-1 exhibited a high value compared to the other loci, suggesting that it is non-neutral. The same Idh-1 locus was implicated in differentiation between temporary and stable populations, as followed also from a highly significant relationship between the allele two of this Idh-1 locus and dispersal power population estimates. The 'parallel evolution' model may account for the diversification of locally adapted Pogonus chalceus populations between different microhabitats.     

Interspecific hybridization and genetic variability of Phlebotomus sandflies

The first successful hybridization is reported between Phlebotomus papatasi and P. duboscqi, two important Old World sandfly vectors of leishmaniasis and other diseases. Laboratory strains of P. papatasi and P. duboscqi were separable by six diagnostic enzyme loci: Est-3, Idh-1, Mdh-2, Mpi, Tre-1 and Tre-3. Hybrids between the two species were verified by the recovery of heterozygous isozyme patterns for the diagnostic loci. No F2 or backcross progeny were obtained. P. papatasi was separated from P. bergeroti by three diagnostic enzyme loci: Est-3, Mpi and Pgd. The isozyme patterns of P. bergeroti contain elements of both P. duboscqi and P. papatasi, although seven diagnostic loci (Est-3, Idh-1, Me, Mpi, Pgd, Tre-1 and Tre-3) separated P. bergeroti from P. duboscqi. Genetic variability profiles of the three species were established for 20 enzyme loci. Three geographically distant strains of P. papatasi from Calcutta, Maharashtra and Israel had isozyme genetic distances of < 0.05. The recently established Calcutta strain showed an unexpectedly low genetic variability with only one (Idh-2) of 20 loci being polymorphic (average heterozygosity of 1.9%) in contrast to 5-8 polymorphic loci (10-12% heterozygosity) in the Maharashtra and Israel strains. Mass and single pair crosses between the three P. papatasi strains were fertile with normal progeny numbers. Thus we found no signs of speciation in P. papatasi.     

Linkage relationships and chromosomal locations of enzyme-coding genes in pepper,Capsicum annuum

The linkage relationships and chromosomal locations of 14 enzyme-coding genes were investigated in Capsicum annuum L. (garden pepper) by monitoring segregations in backcross and F₂ progeny of an interspecific cross between C. annuum cv. NM6-4 and C. chinense CA4 and by studying allele dosage effects in five hybrid primary trisomics. These conclusions can be reached: 6Pgdh-i is on the metacentric chromosome corresponding to the noir trisomie; Idh-1 and Est-3 are on chromosome 12; an aerocentric chromosome which corresponds to the pourple trisomie; Idh-1 is near the centromere and Est-3 is distal on the long arm of that chromosome. The other loci can be arranged in the following linkage groups and are apparently not located on the trisome corresponding to any of the trisomics tested: Est-4-18cM-(Pgi-1-3cM-Pgm-1); Prx-7-2cM-Tk-1; Pgm-2-2cM-Skdh-1; Est-1-OcM-Est-7. Linkage and dosage data combined with karyotype and meiotic analyses of the two species and F₁ hybrids suggest that Idh-1 and Skdh-1/Pgm-2 are near the breakpoints on the two chromosomes involved in a reciprocal translocation for which the two species differ. One locus, Pgm-3, was detected only in C. annuum cultivars and is apparently the result of a duplication of Pgm-2 which codes for cytosolic phosphoglucomutase activity. Pgm-2 and Pgm-3 are not tightly linked (approximately 20% recombination) which supports the proposal that Pgm-3 originated from a mechanism other than unequal crossing over. A comparison of the linkage relationships of enzyme-coding genes in pepper with those of putative orthologous loci in tomato reveals that two linkage blocks, Est-1-Est-7 and Pgi-1-Est-4, may have remained intact since the divergence of Capsicum and Lycopersicon.     

Effects of marked chromosome sections on quantitative traits in the mouse

Summary An investigation of the influences of marked chromosome sections on quantitative traits in a backcross-generation with 2321 mice (C57BL/6JHan × (AKR/NHan×C57BL/6JHan)) is described. In the animals the chromosomes 1, 4, 7, and 8 were marked by the gene loci Idh-1, Gpd-1, Gpi-1s, Es-1, resp. Within the backcross-generation, for Idh-1 and Es-1, more heterozygous genotypes were found than expected under random conditions. By comparing animal-groups with different homologous sections of the marked chromosomes, effects were observed on quantitative traits (body length and weight, dry weight and matter, fat weight and content). The results indicate that a few chromosome sections influence to a major extent the genetic variation of some quantitative traits.This investigation was supported by the Deutsche Forschungsgemeinschaft (Sonderforschungsbereich 146)     

云南松居群遗传学研究的等位酶分析方法

针对１５个云南松Ｐｉｎｕｓｙｕｎｎａｎｅｎｓｉｓ居群,开展了１４种酶系统的水平切片淀粉凝胶电泳实验,在谱带遗传分析的基础上确定了３３个等位酶位点及其等位基因。其中有３２个等位酶位点是多态的（有２个以上的等位基因）,只有一个单态位点Ｄｉａ－４。有３个等位基因的位点有Ｌａｐ－１、Ｌａｐ－２、Ａａ－３、Ｓｋｄ－１、Ｓｋｄ－２、Ａｄｈ－１、Ａｄｈ－３、Ｇｄｈ、Ｐｇｄ－１、Ｐｇｍ－１、Ｐｇｍ－３、Ｐｇｉ－１、Ｐｇｉ－３、Ｍｄｈ－１、Ｍｅ、Ｇ６ｐｄ、Ｄｉａ－１、Ｔｐｉ－１、Ｔｐｉ－２、Ｔｐｉ－３和Ｔｐｉ－４,有４个等位基因的位点有Ｓｋｄ－３、Ａｄｈ－２、Ｐｇｄ－２、Ｍｄｈ－２、Ｍｄｈ－３、Ｍｄｈ－４和Ｄｉａ－２,有５个等位基因的位点有Ａａｔ－１和Ｄｉａ－３。云南松居群的等位基因平均数Ａ＝２１,在松属中居于中上水平。本研究揭示了云南松居群酶位点及其等位基因带谱的变异式样,为松属植物的遗传多样性研究提供了一批酶位点及其等位基因的参考图谱     

Genetic polymorphism, mapping, and characterization of isocitrate dehydrogenase in Anopheles quadrimaculatus

The isocitrate dehydrogenase-2 (Idh-2) locus of Anopheles quadrimaculatus was analyzed genetically and the enzyme was characterized physiochemically. Three-point testcrosses involving chromosome 3 markers showed that in female hybrids the gene sequence and the map distances are: nonstripe (st)--6.8--Idh-2--43.5--short antenna (Sa). Reduced recombination frequencies were observed in male hybrids (st--3.4--Idh-2--25.5--Sa). Idh-2 activity gradually increases during development and reaches a peak intensity in adults. Maximum enzyme activity of Idh-2 was obtained at pH 7.5. One-minute heat treatment at 50 degrees C caused about 50 percent reduction of IDH-2. Ethylene diamine tetraacetic acid (EDTA 5 mM) and p-chloromercuribenzoate (pCMB 10(-5)M) caused complete loss of activity of IDH-2, but pretreatment of the enzyme in situ with mercaptoethanol protected the activity of allozymes from inhibition by pCMB treatment.     

Genetic differentiation in Chilean hake Merluccius gayi gayi (Pisces: Merlucciidae)

The genetic structure of Chilean hake Merluccius gayi gayi, was analyzed using starch gel protein electrophoresis. Samples were collected from four localities along the coast off Chile. A total of 1500 specimens sampled from Coquimbo, San Antonio, Talcahuano and Puerto Montt were used in the study. Genetic information was obtained for six allozyme loci Pgi-1, Pgi-2, Pgm, Idh-1, Idh-2 and Aat. The results of the analysis showed no significant allelic differences among samples from various localities, with an average F_ST value of 0.007 for all loci and samples. A heterogeneity test for all loci and specimens from the four localities showed only two significant values. Thus, Chilean hake populations along the coast of Chile appear to be genetically homogeneous.     

Isozyme analysis of progeny derived from (Allium fistulosum ×Allium cepa) ×Allium cepa

Summary Relatively large quantities of seed were obtained from the interspecific backcross (A. fistulosum xA. cepa) ×A. cepa allowing, for the first time, an extensive study of the heritable traits exhibited by backcross progeny. Two backcross populations, BC1034 and BC1040, distinguished by differentA. fistulosum parents, were characterized for the isozyme markersIdh-1, Adh-1, andPgi-1. Statistical methods are described to calculate cell probabilities for a mixed population of F₂ and BC₁ progeny, using an estimate of the fraction of F₂ progeny in the population derived from the isozyme data. Cell probability distributions were calculated for a mixed population with independent pairs of loci and a mixed population with nonindependent pairs of loci. The isozyme lociIdh-1 andPgi-1 appear to be linked, with a map distance estimated at 33 centimorgans (cM) in BC1034 and 42 cM in BC1040. The probability distribution model for linked loci did not account for all of the distorted segregation ratios inIdh-1 ×Adh-1 orPgi-1 ×Adh-1. The cytological literature does not support linkage betweenIdh-1 ×Adh-1 orPgi-1 ×Adh-1. The distorted segregation ratios for these pairs of loci are likely the result of genetic incompatibilities between the two species.Journal Article No. 1578, Agricultural Experiment Station, New Mexico State University, Las Cruces, NM, USA     

Is natural selection a plausible explanation for the distribution of Idh‐1 alleles in the cricket Allonemobius socius?

Abstract.  1. Allozyme alleles in natural populations have been proposed as either neutral markers of genetic diversity or the product of natural selection on enzyme function, as amino acid substitutions that change electrophoretic mobility may also alter enzyme performance. To address these possibilities, researchers have used both correlative analyses and empirical studies.
2. Here, geographically structured variation of the enzyme isocitrate dehydrogenase ( Idh- 1) in the striped ground cricket Allonemobius socius Scudder (Orthoptera: Gryllidae) is examined. The distributions of Idh- 1 alleles appear to be related to environmental gradients, as allele frequencies showed significant relationships with mean annual temperature and precipitation. Specifically, the slowest mobility allele was more frequent at colder temperatures, while the converse occurred for the fastest mobility allele.
3. An exploratory experiment was performed to examine fitness effects of possessing different Idh- 1 alleles at two temperatures to test the hypothesis that the geographic structure of this locus may reflect environmental adaptation. Results showed that a significant interaction between temperature and Idh- 1 genotype affected the number of eggs laid, with success of homozygous individuals matching environmental expectations.
4. The above results show that (1) variation in the frequency of Idh- 1 alleles is significantly related to environmental gradients in the eastern U.S.A. and (2) alternative alleles of Idh- 1 appear to influence the egg-laying ability of individuals differently depending on environmental temperature. Together, these results suggest that natural selection is a plausible mechanism underlying the distribution of Idh- 1 alleles in this species, although more detailed studies are needed.     

Four independent electrophoretic markers in spadefoot toads

Four enzyme-encoding genes (Idh-1, Idh-2, Ldh-1, and Mdh-1), with alleles diagnostic for the spadefoot toads Scaphiopus multiplicatus and Scaphiopus bombifrons, were investigated in order to characterize their inheritance and linkage relationships. Electrophoretic phenotypes in the offspring of natural crosses exhibit Mendelian segregation, behaving as genotypes produced by alternative alleles at four independently assorting loci. These phenotypes are useful markers of genetic identity and the degree of genetic admixture in the analyses of hybrid zone dynamics for these two species. Concurrent use of a morphological index verified the diagnostic value of the markers. The morphological index is useful for the identification of parental species and many F1 hybrids, however offspring of backcrosses usually express parental species characteristics. Electrophoretic typing allows the identification of all hybrids and 87 percent of the offspring from backcrosses. It also facilitates the identification of tadpoles, which are extremely difficult to distinguish morphologically. The technique is useful for the assessment of introgression and the evaluation of reproductive interaction in these species, even though it slightly underestimates backcross offspring.     

Genetic mapping of a quantitative trait locus (QTL) that enhances the shoot differentiation rate in Hordeum vulgare L.

A quantitative trait locus (QTL) controlling shoot differentiation from immature embryo callus was identified by linkage analysis with morphological and isozyme markers in barley, Hordeum vulgare L. Immature embryos were isolated from cvs Azumamugi (difficult to differentiate), Kanto Nakate Gold (easy to differentiate), their hybrids (F₁) and a backcross population derived from a cross Azumamugi x F₁. The embryos were cultured in vitro for callus initiation and subsequent shoot differentiation. The shoot differentiation rate was closely associated with ear type (v locus), isocitrate dehydrogenase isozyme (Idh-2), and esterase isozyme (Est-11). These markers were found to reside in a chromosome segment of approximately 30cM on chromosome 2. Recombination frequency was 9.9% between v and a proposed QTL named Shd1 (shoot differentiation), 11.5% between Idh-2 and Shd1, and 21.3% between Est-11 and Shd1. All data showed the Idh-2, v, Shdl and Est-11 loci to be arranged in this order from proximal to distal on the long arm of chromosome 2.     

Gene flow analysis demonstrates that Phytophthora fragariae var. rubi constitutes a distinct species, Phytophthora rubi comb. nov

Isozyme analysis and cytochrome oxidase sequences were used to examine whether differentiation of P. fragariae var. fragariae and P. fragariae var. rubi at the variety level is justified. In isozyme studies six strains of both P. fragariae varieties were analyzed with malate dehydrogenase (MDH), glucose phosphate isomerase (GPI), aconitase (ACO), isocitrate dehydrogenase (IDH) and phosphogluconate dehydrogenase (PGD), comprising altogether seven putative loci. Five unique alleles (Mdh-1(A), Mdh-2(B), Gpi(A), Aco(B) and Idh-1(B)) were found in strains of P. fragariae var. fragariae, whereas five unique alleles (Mdh-1(B), Mdh-2(A), Gpi(B), Aco(A) and Idh-1(A)) were present in strains of P. fragariae var. rubi. It was inferred from these data that there is no gene flow between the two P. fragariae varieties. Cytochrome oxidase I (Cox I) sequences showed consistent differences at 15 positions between strains of Fragaria and Rubus respectively. Based on isozyme data, cytochrome oxidase I sequences, and previously published differences in restyriction enzyme patterns of mitochondrial DNA, sequences of nuclear and mitochondrial genes, AFLP patterns and pathogenicity, it was concluded that both specific pathogenic varieties of P. fragariae are reproductively isolated and constitute a distinct species. Consequently strains isolated from Rubus idaeus are assigned to Phytophthora rubi comb. nov.     

Inheritance of Allozyme Loci in Bombina: Second Linkage Group Established

Segregation and linkage relationship of nine allozyme loci, which are fixed for alternative alleles in the European fire-bellied toads, Bombina bombina and B. variegata,were studied using artificial F₁ hybrids to obtain backcross and F₂ progeny. Alleles coding for electromorphs at nine loci (Ldh-1, Mdh-1, Idh-1, Ck, Ak, Gpi, Aat-1, Np, and G6pd)showed Mendelian ratios. Two of the loci, Ak and G6pd, were found to be closely linked (2 cM apart); the other loci assorted independently.     

Gene pool state and degree of infestation by bark beetle (<Emphasis Type="Italic">Ips tipographus</Emphasis> L.) of Norway spruce (<Emphasis Type="Italic">Picea abies</Emphasis> L. Karst.) natural populations and planted stands in Moscow region

A comparative analysis of the gene pool state in natural populations and planted stands of Norway spruce and the degree of their infestation by the bark beetle in the Moscow region was conducted taking into account the dynamic state of communities (4 populations, 148 samples, 24 isoenzyme loci). The degree of infestation by the bark beetle of conditionally native communities is 0%; for planted stands, it is 90–100%; and for a short-term community, it is 15–20%. The comparison of “healthy” populations and those infested with bark beetle by average values of observed heterozygosity (H _O) detected no significant differences. However, the test on allelic frequency heterogeneity demonstrated the difference of planted stands from conditionally native populations both by three loci (Fe-2, Idh-1, Mdh-3) and by the totality of 18 polymorphic isoenzyme loci; the short-term population differs from conditionally native population only by two loci. The value of the inbreeding coefficient by the Idh-1 locus is significantly higher in both populations infested with the bark beetle than in “healthy” populations. The results of conducted studies demonstrate the necessity of continuation of the study on the gene pool state in Norway spruce populations owing to the degree of their infestation by the bark beetle along with the study on the dynamic state of the communities; this can provide a key to solving the problem of the forest preservation from pests.     

Genetic variation and its evolutionary implications in a Mediterranean island endemic lizard

The peculiar bioclimatic and geographic features of Corso–Sardinian islands may provide an ideal scenario for investigating microevolutionary processes, given their large heterogeneity of environments, which could affect dispersal and gene flow among populations, as well as processes of local adaptation. The genetic variation and differentiation among populations of the endemic lizard Archaeolacerta bedriagae were studied by allozyme electrophoresis at 20 presumptive loci. The genetic structure of this species is characterized by relatively high levels of polymorphism and low differentiation among populations. The pattern of genetic differentiation cannot be explained by genetic drift as a function of geographic distance. Genetic distance data show that genetic variation is distributed into three geographically coherent population groups and suggest a recent (Late Pleistocene) origin for the observed geographic fragmentation. The analysis of environmental correlates of allozymic variation indicates a strong correlation of the Idh-1 locus with climatic variables. The frequency of the Idh-1¹⁰⁶ allele is negatively correlated with annual temperature, and positively correlated with annual precipitation. In addition, the observed heterozygosity at this locus decreases towards more arid climatic regimes. The results obtained support the assumption of differential selection acting on Idh-1 allozymes under diverse climates. An association between Idh-1 allozymes and local bioclimatic regimes was also observed for the sympatric lizard Podarcis tiliguerta , suggesting a key role for such selective agents on Idh-1 polymorphism in these two Corso–Sardinian lacertids.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 98 , 661–676.