Polymorphism at the esterase isozyme locus Est10 associated with phylogenetic differentiation in rice

A new esterase isozyme locus, Est10, with 6 alleles including the null form, has been found in rice by using polyacrylamide gel electrophoresis. Thirty F(2) populations of all possible combinations between 5 different band morphs were studied. The segregation pattern indicated that bands 1, 2, 3, 4, and the null form (0) were allelic with each other. The alleles of Est10 were distributed at different frequencies among different varietal groups of rice and also between cultivated rice and its wild relatives (Oryza rufipogon Griff.). Alleles 1 and 2 were frequently found in Japonica and Indica types, respectively. Allele 3 showed a high frequency in Aus and Boro, both Indica types cultivated in South Asia. Allele 4 was frequent in wild rice O. rufipogon. Judging from the linkage between Est10 and RFLP marker RG220 and isozyme marker Est5, Est10 is located on chromosome 1. The importance of this locus in evolutionary studies of rice is discussed.     

Variation at the Est3 locus and adaptability to organophosphorous compounds in Zaprionus indianus populations

Carboxylesterases are enzymes often associated with insect resistance to insecticides. The Est3 locus of Zaprionus indianus Gupta (Diptera: Drosophilidae) harbors four alleles that encode carboxylesterases with potentially detoxifying roles. In this study, we propose a model of resistance to insecticides in Z. indianus based on the adaptability of the Est3 locus inferred from the spread of its alleles over 27 generations in experimental populations, and their frequencies in field populations, which were either exposed or unexposed to the organophosphorous insecticide malathion. The increase in the frequency of this allele in experimental populations, and its high prevalence in field populations exposed to organophosphorous insecticides suggest that natural selection favors individuals with the Est3-3 allele. The low frequency of this allele in unexposed field populations, and the low productivity of Est3-3 homozygotes indicate that an adaptive cost is associated with this allele. The existence of a marker locus for insecticide resistance in Z. indianus makes it possible to use this species as a bioindicator for monitoring the excessive use of organophosphorous products and the emergence of resistance, and to devise strategies for the management of agricultural pests.     

Analysis of linkage between biochemical and morphological markers of 1R-, 2R-, and 5R-chromosomes in rye with autofertility mutations in main incompatibility loci

In F2 hybrids between self-sterile plants of the Volkhova cultivar and self-fertile lines with established self-fertility mutations (sf-mutations) at the major incompatibility loci S (1R), Z (2R), and T (5R), the effect of sf-mutations on the inheritance of secalin-encoding, isozyme, and morphological markers located on the same chromosomes was investigated. Linkage between loci Prx7 and S and locus Sec3 coding for high-molecular-weight secalins on chromosome 1R was shown for the first time The frequency of recombination between Prx7 and Sec3 and between S and Sec3 was 29.1 +/- 4.8% and 30.9 +/- 7.0%, respectively. Independent inheritance of locus Z and isozyme markers of chromosome 2R, Est3/5 and beta-Glu, from locus Sec2 encoding 75-kDa gamma-secalins was shown; in hybrids, the recombination frequency between Est3/5 and locus Z varied from 19.2 +/- 8.1 to 50%. Independent inheritance of morphological (Ddw and Hs) and isozyme markers (Est4, Est6/9, and Aco2) of chromosome 5R from locus T located on the same chromosome was demonstrated.     

西藏和埃塞俄比亚大麦6个同工酶位点遗传变异的对比分析

我们对比分析了埃塞俄比亚(简称埃)和西藏共777份栽培大麦材料在6个同工酶位点(Est1、Est2、Kst3、Est4、Acp1和Got1)的遗传变异。结果表明,无论是从单个位点上分析还是在多位点基因组合形式上评价,埃大麦与西藏大麦群体在遗传组成和多位点基因结构上都有着很大的差异。遗传多样性对比分析表明,从单个位点基因类型看,西藏大麦与埃大麦遗传变异程度大致相当,但从多位点基因组合形式看,西藏大麦遗传多样性程度极显著地高于埃大麦。     

Genetic control of leucine aminopeptidase and esterase isozymes in the interspecific cross Cucurbita ecuadorensis x C. maxima

Starch gel electrophoretic analyses of crude seed extracts of Cucurbita ecuadorensis, C. maxima, their F₁ and F₂, and three of the four possible interspecific backcrosses reveal that the genus is polymorphic for alpha-naphthyl acetate esterases (Est) and leucine aminopeptidase (LAP). The two electrophoretic forms of both Est and LAP are controlled by codominant alleles. The two loci do not exhibit linkage. Neither the LAP nor the Est phenotypes exhibit a significant deviation from the expected 1:1 ratio in interspecific backcrosses when the donor parent alleles are transmitted through female gametes, but there is a significant deviation for Est when transmission is through male gametes. Differential gametic selection involving the Est-1 locus suggests structural differences between the genomes of the parental species for the chromosomal region in which this locus occurs. No structural differences are indicated between the parental genomes for the chromosome region bearing the Lap-1 locus.     

The genetics and expression of an esterase locus inAnopheles gambiae

The main polymorphic system of esterase isoenzymes in adults of the G3 laboratory strain ofAnopheles gambiae consists of two to five major bands of activity per individual. The bands are designated 5S, 5F, 13, 14, and 15. In genetic crosses, the genes which coded for the bands assorted as three codominant alleles, Est A, Est B, and Est C, at a single autosomal locus. Homozygotes for the Est C allele were significantly underrepresented among backcross progeny. The developmental pattern of esterase expression was examined. Esterase gene expression in embryos was first detectable between 2 and 12 hr after oviposition. The initiation or termination of expression of some of the bands corresponded to boundaries between developmental stages. Most of the esterase fractions were not specifically localized within the tissues tested, with the exception of a series of bands which were restricted largely to adult male testes.     

Variabilité génétique entre les populatiosn de Speonomus zophosinus

Genetic variability was examined in six troglobitic populations of Speonomus zophosinus which were limited to a very small geographical area. Results indicate a high genetic variation and a high degree of heterozygosity (H 0.43). The genetic variability observed between the populations reveals the existence of two genetically heterogeneous groups (one upstream, one downstream. There are significant differences in the frequency of the six alleles of the locus Est 3 found in these two groups.     

Genetic polymorphism at two linked loci,Sod and Est-6, in Drosophila melanogaster

We have examined the patterns of polymorphism at two linked loci, Sod and Est-6, separated by nearly 1000 kb on the left arm of chromosome 3 of Drosophila melanogaster. The evidence suggests that natural selection has been involved in shaping the polymorphisms. At the Sod locus, a fairly strong (s>0.01) selective sweep, started ≥2600 years ago, increased the frequency of a rare haplotype, F(A), to about 50% frequency in populations of Europe, Asia, and the Americas. More recently, an F(A) allele mutated to an S allele, which has increased to frequencies 5–15% in populations of Europe, Asia and North America. All S alleles are identical (or very nearly) in sequence and differ by one nucleotide substitution (which accounts for the F→S electrophoretic difference) from F(A) alleles. At the Est-6 locus, the evidence indicates both directional and balancing selection impacting separately the promoter and the coding regions of the gene, with linkage disequilibrium occurring within each region. Some linkage disequilibrium also exists between the two genes.     

Evidence for Positive Selection in the Superoxide Dismutase (Sod) Region of Drosophila Melanogaster

DNA sequence variation in a 1410-bp region including the Cu,Zn Sod locus was examined in 41 homozygous lines of Drosophila melanogaster. Fourteen lines were from Barcelona, Spain, 25 were from California populations and the other two were from laboratory stocks. Two common electromorphs, SOD(S) and SOD(F), are segregating in the populations. Our sample of 41 lines included 19 Sod(S) and 22 Sod(F) alleles (henceforward referred to as Slow and Fast alleles). All 19 Slow alleles were identical in sequence. Of the 22 Fast alleles sequenced, nine were identical in sequence and are referred to as the Fast A haplotypes. The Slow allele sequence differed from the Fast A haplotype at a single nucleotide site, the site that accounts for the amino acid difference between SOD(S) and SOD(F). There were nine other haplotypes among the remaining 13 Fast alleles sequenced. The overall level of nucleotide diversity (π) in this sample is not greatly different than that found at other loci in D. melanogaster. It is concluded that the Slow/Fast polymorphism is a recently arisen polymorphism, not an old balanced polymorphism. The large group of nearly identical haplotypes suggests that a recent mutation, at the Sod locus or tightly linked to it, has increased rapidly in frequency to around 50%, both in California and Spain. The application of a new statistical test demonstrates that the occurrence of such large numbers of haplotypes with so little variation among them is very unlikely under the usual equilibrium neutral model. We suggest that the high frequency of some haplotypes is due to natural selection at the Sod locus or at a tightly linked locus.     

Cleft palate: more genetic lessons from mice

Cleft palate occurred in high frequency (14%) in the F2 generation of the cross between two stocks of mice, LGG and SELH, neither of which produces more than 2% cleft palate. The cleft palate trait results from a new combination of alleles that is not present in either parental stock. The lack of cleft palate in the F2 generation after outcrosses of both parental stocks to other strains shows that this new combination of alleles has specific contributions from both parental strains, and also that there must be at least two loci involved. A deficiency of Mod-1 homozygotes in the SELH/LGG F2 adults suggests that one of the loci involved may be linked to Mod-1 and that the number of loci involved is few. Significantly more F2 males (19%) than females (9%) were affected with cleft palate. The data can be explained by a two-locus epistatic model with a dominant mutation (P) at one locus that causes cleft palate when not suppressed by or compensated for by a dominant allele (S) at a second locus. The parental stocks would be PPSS and ppss. In the F2 generation, the new combinations PPss and Ppss would express cleft palate, a total expected of 19%. Similar new combinations of alleles at two loci may explain some instances of high occurrence of cleft palate or other developmental threshold traits in previously unaffected human families.     

Genetic variation at a pig serum protein locus, Po-2 and its assignment to the Phi, Hal, S, H, Pgd linkage group

Two-dimensional agarose gel (pH 5.4)-polyacrylamide gel (pH 9.0) electrophoresis of pig serum samples revealed a new serum protein (postalbumin-2, PO-2) polymorphism. Family data supported the hypothesis that the three PO-2 phenotypes observed were controlled by two codominant, autosomal alleles (Po-2F and Po-2s) at a single locus. The frequency of Po-2F in Swedish Landrace and in Swedish Yorkshire breeds was estimated at 0.74 and 0.65, respectively. Evidence was presented for close genetic linkage between Po-2 and the red cell phosphohexose isomerase locus (Phi). A recombination frequency of 3.2% was obtained from double backcross material. Data obtained in a Danish Landrace material showing linkage between the Po-2 locus and the H blood group locus, the Pgd locus and Hal (locus for halothane sensitivity) are also given. A total of seven recombinants were observed. They show that Po-2 is a new locus in a previously established linkage group. The likely sequence of the loci is: Phi, Hal, S, H, Po-2, Pgd.     

Genetic analysis of disease resistance to all strains of BaYMV in a Chinese barley landrace, Mokusekko 3

 A Chinese landrace of barley, Mokusekko 3, is unique in being completely resistant against all strains of barley yellow mosaic virus (BaYMV). The present investigation revealed that the resistance of Mokusekko 3 is governed by two recessive genes. As one of the resistance genes was known to be tightly linked with alleles at the Est complex locus, consisting of the Est1, Est2 and Est4 loci for esterase isozymes, each of the resistance genes could be separated by means of marker-assisted selection using an isozyme allelic combination as a marker. One of the resistance genes, ym1, is linked to K (hooded lemma) and gl3 (glossy leaf 3) with recombination values of 25.3% and 9.7% respectively, and these three genes are located in the order K-gl3-ym1 on chromosome 4. Another newly designated resistance gene, ym5, is linked to alleles at the Est complex locus and cu2 (curly growth 2), with recombination values of 1.9% and 19.5% respectively, in the order cu2-Est-ym5 from proximal to distal on the long arm of chromosome 3. The complete resistance of Mokusekko 3 is caused by combining two resistance genes, ym1 and ym5. However, almost all the “resistant” cultivars derived from crosses with Mokusekko 3 are susceptible to the recently detected strain BaYMV-III in Japan, since they contain only one resistance gene, ym5. Marker-assisted selection to combine resistance genes into a cultivar is discussed for the breeding of stabilizing resistance to BaYMV. Received: 23 September 1996 / Accepted: 8 November 1996     

Thermal adaptive significance of ADH and EST-6 allozymes in Indian geographical populations of Drosophila melanogaster

Indian geographical populations of Drosophila melanogaster exhibit significant correlation (r 0.95) of allelic frequencies at Est -6 and Adh loci with latitude as well as altitude. Est -6^S and AdhF allozymes are well adapted to colder environments while Est -6^F and AdhS are warm adapted. The data on allozymic clines match climatic conditions on the Indian subcontinent. On the basis of multiple regression analysis, one major conclusion is that coefficient of variation of temperature ( T _CV) along latitude/altitude accounts for alterations in allelic frequency at the Adh locus while T _max and T _max explain changes at the Est -6 locus. Thus, climatic conditions lead to thermal selection of allozymes in Indian populations of D. melanogaster .     

Concordance of allozyme and microsatellite differentiation in a marine fish, but evidence of selection at a microsatellite locus

Previous studies have reported higher levels of divergence for microsatellites than for allozymes in several species, suggested to reflect stabilizing selection on the allozymes. We compared the differentiation patterns of 11 allozyme and nine microsatellite loci using 679 spawning Atlantic herring (Clupea harengus) collected in the Baltic and North Seas to test for differential natural selection on these markers. Observed distributions of F statistics for the two types of markers are conspicuously dissimilar, but we show that these differences can largely be explained by sampling phenomena caused by different allele frequency distributions and degrees of variability. The results show consistently low levels of differentiation for both marker types, with the exception of one outlier microsatellite locus with a notably high F(ST). The aberrant pattern at this locus is primarily due to two alleles occurring at markedly high frequencies in the Baltic, suggesting selection at this locus, or a closely linked one. When excluding this locus, the two marker types show similar, weak differentiation patterns with F(ST) values between the Baltic and the North Seas of 0.001 and 0.002 for allozymes and microsatellites, respectively. This small heterogeneity, and weak isolation by distance, is easier to distinguish statistically with microsatellites than with allozymes that have fewer alleles and skewed frequency distributions. The allozymes, however, also detect surprisingly low levels of divergence. Our results support suggestions that previously described differences between marker types are primarily caused by a small number of outlier loci.     

Inheritance of grain esterase genes in rye populations (Secale cereale L.)

Genetic analysis of four tow straw rye populations has been carried out basing on the trait electrophoretic spectrum of grain esterase isozymes. Expression of seven independent Est genes has been shown. Three of them are clustered and their intrapopulation polymorphism exceeds two alleles. Comparative analysis of the frequences of different genes in parental populations and in F2 with literature data about localization of Est genes makes it possible to carry out chromosomal localization of the genes identified according to the fact of presence or absence of linking with the genes of rye self-incompatibility.     

Geographic distribution of alleles at the Ga2 locus for segregation distortion in barley

Summary A distorted segregation of esterase alleles at the complex loci, Est1, Est2 and Est4, was found in an F₂ population. This distortion is typical for cross combinations between the Ga2Ga2 and ga2ga2 genotypes responsible for segregation distortion, since the Ga2 locus is linked with the complex loci encoding the esterase isozymes. The segregation of esterase isozyme patterns in F₂ populations between 473 varieties of barley and a tester of ga2ga2 genotype was examined, and the genotypes inducing segregation distortion were detected. Varieties with a ga2ga2 genotype are widely distributed throughout the world, whereas Ga2Ga2 varieties are found only in eastern and southern regions of Asia, from Japan to North India, with a low frequency. In varieties collected from these regions, some associations were detected between alleles at the Ga2 locus and esterase isozyme patterns. Additionally, most of the Ga2 barley varieties are naked and possess a BtBtbt2bt2 genotype for a non-brittle rachis.     

Distorted segregation of the esterase isozyme genotypes in barley (Hordeum vulgare L.)

Distorted segregation of the esterase isozyme genotypes was observed in F2 population which was produced from a cross combination between 'Ko A' and 'Mokusekko 3' of barley varieties. After examining the segregation of esterase isozyme genotypes in B1F1 hybrids derived from the reciprocal backcrosses, it was made clear that the distorted segregation was caused by certation between pollens of different genotypes, independent of the female genotypes. Furthermore, the certation was controlled by a newly designated gene, Ga2, at the locus which was linked with the multiocus, Est1, Est2 and Est4, for esterase isozymes at the long arm of chromosome 3. The distorted segregation ratios did not significantly vary among F2 populations derived from F1 hybrids of the same combination which were grown in different years. Mechanically mixed pollens of the parents, however, could not induce the certation.     

ESTERASE VARIATION AND GENETIC STRUCTURE IN THREE GEOGRAPHIC POPULATIONS OF SITODIPLOSIS MOSELLANA (GEHIN) (DIPTERA: CECIDOMYIIDAE) IN WESTERN CHINA*

Abstract This paper investigates the esterase variation and genetic structure in three geographic populations of Sitodiplosis mosellana (Géhin) in western China by PAGE. The localities surveyed are Gaolan (36.3°N, 103.9°E) and Wuwei (37.9°N, 102.6°E) in spring wheat region and Chang'an (34. 1°N, 108.9° E) in winter wheat region. The results suggest that the esterase is coded by two loci: Est‐1 and Est‐2. Est‐1 is coded by a plastogene producing only one band that is the fastest on the gel among all bands. The Est‐2 is duplicated loci with 8 alleles, namely, a, b, c, d, e, f, g, h, which produce altogether 8 bands in all the populations and 1–4 bands in individual samples. There are 19 zymogram types observed in the three geographic populations. Seventeen zymogram types emerge in Chang'an population, but 5 and 4 zymogram types are found respectively in Gaolan and Wuwei populations. II₂ zymogram type is the commonest in all the populations. The alleles that had the highest frequencies in all the populations are d, e, g. All 8 alleles at the Est2 were observed in Chang'an population, but only total 3 alleles‐d, e, g at the Est‐2 appeared in Gaolan and Wuwei populations. The analysis of genetic identity and cluster (UPGMA) on the alloenzyme indicates that the relationship between the two populations of spring wheat region seems to be closer, as compared with the relationship between spring wheat population and winter wheat population. It is evident that there exists some infraspecific variation caused mainly by genetic drift in S. mosellana and the gene flow among the populations possibly took place to some extent.     

Polymorphism of intron-1 in the voltage-gated sodium channel gene of Anopheles gambiae s.s. populations from Cameroon with emphasis on insecticide knockdown resistance mutations

Sequence variation at the intron-1 of the voltage-gated sodium channel gene in Anopheles gambiae M- and S-forms from Cameroon was assessed to explore the number of mutational events originating knockdown resistance ( kdr ) alleles. Mosquitoes were sampled between December 2005 and June 2006 from three geographical areas: (i) Magba in the western region; (ii) Loum, Tiko, Douala, Kribi, and Campo along the Atlantic coast; and (iii) Bertoua, in the eastern continental plateau. Both 1014S and 1014F kdr alleles were found in the S-form with overall frequencies of 14% and 42% respectively. Only the 1014F allele was found in the M-form at lower frequency (11%). Analysis of a 455 bp region of intron-1 upstream the kdr locus revealed four independent mutation events originating kdr alleles, here named MS1 -1014F, S1-1014S and S2-1014S kdr- intron-1 haplotypes in S-form and MS3-1014F kdr- intron-1 haplotype in the M-form. Furthermore, there was evidence for mutual introgression of kdr 1014F allele between the two molecular forms, MS1 and MS3 being widely shared by them. Although no M/S hybrid was observed in analysed samples, this wide distribution of haplotypes MS1 and MS3 suggests inter-form hybridizing at significant level and emphasizes the rapid diffusion of the kdr alleles in Africa. The mosaic of genetic events found in Cameroon is representative of the situation in the West–Central African region and highlights the importance of evaluating the spatial and temporal evolution of kdr alleles for a better management of insecticide resistance.     

Populationsgenetische Untersuchungen anSaccharomyces Cerevisiae. II. Der Einfluß von Esterase-Loci auf Genfrequenzverändernde Faktoren

The influence of two esterase loci, each possessing two alleles (Est1 _s ,Est1 _f andEst2 _s ,Est2 _f ), on the rate of reproduction in haploid yeasts (Saccharomyces cerevisiae) during the vegetative phase, as well as on the rate of meiosis and on the vitality of spores was investigated. Alleles of theEst1 locus had no apparent effect on the rate of vegetative reproduction. In contrast, genotypes with theEst2 _f allele possessed a definite selective advantage. Whereas theEst2 locus had no demonstrable influence on meiosis,Est1 _s /Est1 _s homozygotes, in contrast to the other two genotypes, exhibited an increased rate of meiosis. A connection between spore lethality and those esterases in question could not be demonstrated.