Genetics of two tissue esterase polymorphisms (Est-4 and Est-5) in the rabbit

Two polymorphic esterase systems were found after electrophoresis of rabbit tissue homogenates. Each of these systems is controlled by an autosomal locus with two alleles. Est-4 determines the absence (Est-4^a) or presence (Est-4^b) of two bands of esterase activity with intermediate anodal mobility and broad substrate specificity. This polymorphism was found to be present in liver, small intestine, and spleen but not in kidney, heart, and testis. Est-5 is coding for cathodally migrating esterases which differ in mobility (Est-5^a and Est-5^b). This polymorphism was found only in kidney and testis homogenates. Est-5 esterases are more active against -naphthyl acetate than against -naphthyl acetate and have no activity against -naphthyl butyrate. Linkage analysis indicated that Est-4 is localized on rabbit LG VI as part of a cluster of esterase loci, whereas Est-5 segregates independently. Rabbits from two inbred and nine partly inbred strains were tested for these polymorphisms.This investigation was supported in part by Public Health Service Research Grant RR-00251 from the Division of Research Resources and by funds from the University of Utrecht. The Jackson Laboratory is fully accredited by the American Association for Accreditation of Laboratory Animal Care.     

Genetics of a tissue esterase polymorphism (Est-6) in the rabbit (Oryctolagus cuniculus)

Genetic analysis of a polymorphic tissue esterase revealed a new locus (Est-6) with two alleles (Est-6 ^a andEst-6 ^b) on linkage group VI of the rabbit.Est-6 is closely linked to theEst-1,2,4 cluster. Esterase ofEst-6 is found in many organs, particularly in liver and small intestine, but not in erythrocytes and serum.Est-6 esterase hydrolyzes -naphthyl acetate and butyrate, naphthol AS-D acetate, indoxyl acetate, and butyrate as well as 5-bromoindoxyl acetate,N-acetyl-l-alanine--naphthyl ester but not 4-methylumbelliferyl acetate and fluorescein diacetate. The enzyme is inhibited by bis-p-nitrophenyl phosphate and eserine but not byp-chloromercuribenzoate. It was classified as a carboxylesterase (EC 3.1.1.1). Based on chromosomal localization, tissue distribution, substrate specificity, inhibitor sensitivity, and range ofpI's, rabbitEst-6 is assumed to be homologous with mouseEs-7.The contribution of Dr. O. von Deimling (No. 59) was supported by the Deutsche Forschungsgemeinschaft (De 315/2-2).     

Variation,geographical distribution and genetical analysis of esterase isozymes in foxtail millet,Setaria italica (L.) P. Beauv.

Summary The esterase isozymes of 432 strains of foxtail millet, Setaria italica (L.) P. Beauv., collected from different areas throughout Eurasia, were investigated by gel isoelectric focusing. Five phenotypes were recognized, based on the combination of five major activity bands. Cross experiments among different phenotypes revealed these isozymes to be controlled by two codominant alleles and a null allele on the locus, Est-1, and three codominant alleles on another independent locus, Est-2. On locus Est-1, 388 strains had Est-1 ^a, 41 had Est-1 ^b and three had Est-1 ^null alleles. Est-1 ^a was widely distributed throughout Eurasia, while the distribution of Est-1 ^b and Est-1 ^null was distinctly restricted. On locus Est-2, 417 strains had Est-2 ^a, nine had Est-2 ^b and six had Est-2 ^c alleles. Est-2 ^a was widely distributed throughout Asia to Czechoslovakia, but was not detected in the western part of Europe. Est-2 ^b was found in all of the strains from the western part of Europe and in one of the Indian strains. Est-2 ^c was rarely found in Japan and China. The distribution of Est-2 ^a and -2 ^b might indicate some degree of phylogenetic differentiation between the Asian and the European strains. Polymorphism in both loci was observed only in Chinese strains.Contribution No. 30 from the Plant Germ-plasm Institute, Faculty of Agriculture, Kyoto University, Kyoto, Japan     

Genetic linkage relationships between two enzyme loci,Est-2 and acph,in the mosquito Aedes (Finlaya) togoi

An esterase locus (Est-2), coding for carboxylesterase, and an acid phosphatase locus (Acph) were genetically studied by agar gel electrophoresis in the mosquito Aedes (Finlaya) togoi. The Est-2 and Acph variants occur as a monomer and a dimer, respectively. Both enzyme loci are linked to the sex locus (M) and s (straw-colored larva); the gene arrangement and recombination distances were Est-2—12.6%—s—31.7%—M—2.9%—Acph—3.2%—Est-3. The Est-3 locus was previously shown to code for carboxylesterase.This work was supported by Grant AI 16983-02 from the National Institutes of Health, Bethesda, Md.     

Linkage studies on an esterase locus in the mosquito Aedes togoi

An electrophoretic survey of esterases in 7 wild-type and 10 mutant strains of the mosquito Aedes (Finlaya) togoi was undertaken using thin-layer agar gels. Three esterases (designated the Est-1, Est-2, and Est-3 loci in decreasing order of electrophoretic mobility) could be detected from fourth-instar larvae, pupae, and 2- to 5-day-old adults. Homogenates of the larvae gave the most intensely stained bands in the gels, especially for Est-3. The three esterases were designated carboxylesterases based on their response to the two esterase inhibitors, eserine and paraoxon (diethyl-p-nitrophenyl phosphate). The Est-3 locus was found to have five alleles including at least one null. The linkage results of six backcrosses suggest that Est-3 is located only 5–8 map units from the sex allele (m) and the gene arrangement is Est-3-m-s (straw-colored larva) in linkage group I.This work was supported by National Institutes of Health Grant AI 16983-01.     

Serum esterase genetics in rabbits. II. Genetic analysis of the prealbumin esterase system,including atropinesterase and cocainesterase polymorphism

The zymotypic variation of rabbit prealbumin esterases is controlled by three autosomal loci, each with two alleles: Est-1 ^S and Est-1 ^s, Est-2^F and Est-2 ^f′, Est-3^D and Est-3 ^d. Est-1^S gives rise to the three S zones possessing the cocainesterase activity, Est-2 ^F to the three F zones with atropinesterase activity. Presence of the latter allele is never manifested without the Est-1 ^S allele. Est-3 ^D codes for the D zone. This D esterase reacts with the currently used substrate α-naphthylacetate only in the presence of the F zones. Est-1 and Est-2 loci are closely linked (<0.5% recombination); Est-3 shows no coupling with Est-1 and Est-2. The Est-1 ^S and Est-3 ^D alleles have a complete dominant expression, whereas the Est-2 alleles are codominant. Gene frequencies of the Est-1 and Est-2 loci vary between the examined breeds. A Hardy-Weinberg equilibrium is found in two populations (Cpb:ALU and Cpb:VW). A significant surplus of heterozygotes is demonstrated in a third population (Cpb:CH).     

Origin of males in Melipona subnitida estimated from data of an isozymic polymorphic system

In a population of the social bee Melipona subnitida of about 200 hives, from Mossoró, Northeastern Brazil, 54 hives were sampled and studied electrophoretically as far as the alleles Est-3 ^S, Est-3 ^M and Est-3 ^F were concerned. Males are produced by eggs laid by workers (no more than 4 in the same day) and by the queen. It was estimated that 61.2% of the drones are sons of the queen and 38.8% are sons of the workers. With these values the effective number (Ne) was estimated in 395.80 which is 24% higher than in a model in which all males are sons of the queen.     

Genetic characterisation of a further homoeoallelic series of grain esterase loci,Est-6, in wheat

Summary Isoelectric focussing in alkaline pH gels has permitted the identification of a new homoeoallelic series of genes,Est-6, encoding grain esterases in bread wheat,Triticum aestivum. Nullisomic analysis located these genes to the short arms of the homoeologous group 2 chromosomes. A search for polymorphism withinEst-6 revealed null alleles at each ofEst-A6,Est-B6 andEst-D6. A further homoeolocus,Est-M6, is present on chromosome arm2MS ofAegilops comosa.     

Esterase genes in Daphnia pulex: linked inheritance and genotypic distribution in natural populations

Summary Esterase patterns were examined in three populations of Daphnia pulex. The total number of bands showing esterase activity was 17. Three major genes Est-1, Est-2, Est-3 controlling esterase synthesis were identified and genetically studied. These genes were found to be located in the same linkage group. It was shown that two or three homologous chromosomes differing in sets of esterase alleles predominantly occur in the populations considered.     

Genetic diversity of six isozyme loci in cultivated barley of Tibet

Summary A random sample of 463 accessions of cultivated barley from the Tibet Hordeum germplasm collection was assayed electorphoretically for genetic diversity at six isozyme loci. Two loci (Acp-1 and Got-1) were found to be monomorphic and extensive variation was detected at the remaining four loci (Est-1, Est-2, Est-3 and Est-4). The allelic composition of Tibetan barley appeared to be distinct as compared to the results of previous studies of barleys from other parts of the world. Partitioning of genetic diversity showed that approximately 96% of the total variation was maintained at the within-subregion level and only about 4% was accounted for by differentiation among the eight subregions. Analysis of multilocus genotypes revealed non-random association of the alleles at the four loci, both in the entire sample and in all the subregions, although the four major multilocus genotypes did not show significant departure from the expectation based on complete random association. The possible causes for the establishment of these multilocus associations were discussed.     

Genetic diversity of four esterase loci in natural populations of Hordeum spontaneum C. Koch from Jordan

Summary The diversity of four esterase loci was studied electrophoretically in 690 individual spikes representing 12 populations of wild barley (Hordeum spontaneum C. Koch.) collected from central, peripheral and marginal regions of its distribution in Jordan. A minimum of 6, 10, 5 and 5 alleles were observed at the Est-1, Est-2, Est-4 and Est-5 loci, respectively. Est-2 and Est-4 were the most diverse loci (H_c=0.53±0.05 and 0.46±0.07, respectively). Est-5 was intermediate (H_c=0.33+0.07) and Est-1 was the lowest (H_c=0.22±0.04). Polymorphism was highest in the central populations (H_e=0.52±0.04), followed by the peripheral (H_e=0.40±0.05) and the marginal (H_e=0.22±0.05) populations. Average allelic diversity between (G_st=0.49) and within (H_s=0.51) populations reflects a high allelic differentiation among these populations. Log-linear analyses revealed that four two-locus terms and two three-locus terms were significantly associated (P<0.05). Geographical distances between populations were not significantly correlated with Nei's genetic similarity index (r=0.16; P<0.19). It is postulated that diversifying selection is a major factor in the population genetic differentiation of these esterase loci.     

Genetics of three esterase loci in Anopheles stephensi liston

A survey of laboratory strains of Anopheles stephensi for nonspecific esterases by polyacrylamide gel electrophoresis revealed 10 zones of esterase activity. In 3 of the 10 zones, three electromorphs were observed. Genetic analysis revealed that these three zones are controlled by three loci, viz., Est-3, Est-4, and Est-5, and that the electromorphs are codominant alleles at each locus. The three esterase loci were found linked to each other and to an autosomal marker colorless-eye. The esterase loci have tentatively been placed in linkage group II. The probable gene sequence on chromosome 2 is either c-Est-3-Est-4-Est-5 or c-Est-4-Est-3-Est-5.     

Associations of Alleles of the Esterase-1 Locus with Gene Arrangements of the Left Arm of the Second Chromosome in DROSOPHILA ROBUSTA

Evidence of strong associations of Est-1 alleles with the 2L, 2L1 and 2L3 gene arrangements of the left arm of the second chromosome in D. robusta is presented. Each gene arrangement is polymorphic for three to four Est-1 alleles. The allele frequencies differ in the 2L3 and 2L arrangements; the allele Est-1^.92 is 8% in the 2L3 arrangement (n=203)—this allele is 82% in the 2L arrangement (n=203); the allele Est-1^1.0 is 66% and 14.8% in the 2L3 and 2L arrangements, respectively. There are no differences in allele frequencies in 2L3 arrangements from any of the widely separated seven different populations; similarly the allele frequencies in the 2L arrangement are alike in all five widely separated populations studied. The allele frequencies in the 2L1 arrangement are intermediate to those observed in the 2L3 and the 2L arrangements and show north-south clinal change. These associations between Est-1 alleles and gene arrangements of the left arm of the second chromosome are due to natural selection favoring different allele frequencies in different gene arrangements, as a result of epistatic interactions between the Est-1 locus and the loci on the gene arrangements. As expected, we observe that the proportion of heterozygotes is greater in the inversion heterokaryotypes than in the homokaryotypes.     

Esterases in the mosquito Culex pipiens pipiens L.: Formal genetics and polymorphism of adult esterases

The genetics of two esterase loci active in autogenous adults of the mosquito Culex pipiens pipiens L. has been studied by means of starch gel electrophoresis. Three alleles at the Est-1 locus and eight at the Est-2 locus are described. Both loci have a null allele. Active alleles are codominant and there is no hybrid enzyme in heterozygotes. The Est-1 locus codes esterases preferentially hydrolyzing -naphthylacetate and the Est-2 locus esterases preferentially hydrolyzing -naphthylacetate. Strains homozygous for both loci were selected. Linkage studies of the two loci have shown that they are not sex linked but are linked to each other, the crossover frequency being 8.6%. The polymorphism of two laboratory and two natural populations is described for both loci. Phenotypic distributions are in good agreement with Hardy-Weinberg expectations.This work was conducted at the Université des Sciences et Techniques du Languedoc (Laboratoire de Génétique Expérimentale des Populations), Montpellier, France, in partial fulfillment of the requirements for the degree of Docteur de spécialité.     

Characterization of Esterases in a Brazilian Population of Zaprionus Indianus (Diptera: Drosophilidae)

The aim of this study was to characterize esterases in Zaprionus indianus, a drosophilid recently introduced into Brazil. A further aim was study the variation of activity of esterases in the presence of inhibitors and their expression according to sex, sexual activity and age of individual flies. Polymorphisms were detected in two esterase loci (Est-2 and Est-3) and monomorphisms in four others (Est-1, Est-4, Est-5 and Est-6). Biochemical tests using α- and β-naphthyl acetate and the inhibitors malathion, eserine sulphate and PMSF allowed us to classify EST-2 and EST-5 as β-esterases, both carboxyl-esterases, and EST-1, EST-3, EST-4 and EST-6 as α-esterases. EST-1 and EST-3 were classified as carboxyl-esterases and EST-4 and EST-6 as cholinesterases. EST-5 activity was more pronounced in males and EST-2 was restricted to them or to recently copulated females. EST-4, rarely detected, was not characterized. Based on their biochemical characteristics possible roles for these enzymes are suggested.     

Molecular evolution of two linked genes, Est-6 and Sod, in Drosophila melanogaster.

We have obtained 15 sequences of Est-6 from a natural population of Drosophila melanogaster to test whether linkage disequilibrium exists between Est-6 and the closely linked Sod, and whether natural selection may be involved. An early experiment with allozymes had shown linkage disequilibrium between these two loci, while none was detected between other gene pairs. The Sod sequences for the same 15 haplotypes were obtained previously. The two genes exhibit similar levels of nucleotide polymorphism, but the patterns are different. In Est-6, there are nine amino acid replacement polymorphisms, one of which accounts for the S-F allozyme polymorphism. In Sod, there is only one replacement polymorphism, which corresponds to the S-F allozyme polymorphism. The transversion/transition ratio is more than five times larger in Sod than in Est-6. At the nucleotide level, the S and F alleles of Est-6 make up two allele families that are quite different from each other, while there is relatively little variation within each of them. There are also two families of alleles in Sod, one consisting of a subset of F alleles, and the other consisting of another subset of F alleles, designed F(A), plus all the S alleles. The Sod F(A) and S alleles are completely or nearly identical in nucleotide sequence, except for the replacement mutation that accounts for the allozyme difference. The two allele families have independent evolutionary histories in the two genes. There are traces of statistically significant linkage disequilibrium between the two genes that, we suggest, may have arisen as a consequence of selection favoring one particular sequence at each locus.     

Inheritance of some marker genes in Setaria italica (L.) P. Beauv.

Summary A study on a series of genetic markers was run on five hybrids of foxtail millet, Setaria italica, and on one interspecific hybrid S. viridisxS. italica (S. viridis is the wild relative of S. italica). Seven enzymatic systems were investigated using starch gel electrophoresis (esterase, alcohol dehydrogenase, glutamate oxaloacetate transaminase, acid phosphatase, malate dehydrogenase, 6-phosphogluconate dehydrogenase, cathodic peroxidase). This genetic analysis of the 6 F2 has allowed us to define 12 polymorphic loci: Est-1, -2 and -3, Adh-1, Got-1 and -2, Acph-1, Mdh-1 and -2, Pgd-1 and -2, and Pox-1. All of them behaved like dimers, except Est-1 and Est-2 which showed monomeric structures. Two other markers were examined: waxy endosperm, which appeared to be controlled by one locus, and anthocyanic pigmentation of the collar, for which at least two loci are responsible. Studies of linkage carried out on three F2 showed two linkage groups: Mdh-1, Pox-1, Wx, Est-3, and a locus for collar colour, and Est-2, and one or two other loci of colouring.     

Species relationship in the Pennisetum gene pool: enzyme polymorphism

Summary Variation in leaf esterases (EST), 6-phosphogluconate dehydrogenase (PGD), shikimate dehydrogenase (SKDH), leucine aminopeptidase (AMP), phosphoglucomutase (PGM) and malate dehydrogenase (MDH) is reported in the Pennisetum gene pool. In the primary gene pool, polymorphism for EST, AMP, SKDH was very high, as compared to the near-monomorphic isozymes of PGD. Two loci controlling leaf esterases Est-1 and Est-2, were identified in the primary gene pool. Differences in allelic frequency distribution of the polymorphic Est-1 locus occur between the cultivated and wild pearl millet. The prevalent alleles of Est-1 are absent in P. purpureum Schumach (secondary gene pool). A monomorphic band of the -esterase-specific Est-2 locus was identified in most of the secondary gene pool accessions, P. squamulatum Fresen and an accession of P. pedicellatum. SKDH and EST revealed differences between most of the tertiary gene pool species. By contrast, a PGD zymogram was prevalent in several species of different sectional taxa. Gene duplication for PGD isozymes occurs in the diploid species, P. ramosum, of the tertiary gene pool. Heterodimers of PGD and EST were observed in the hybrid between pearl millet and P. squamulatum, whereas a monomeric structure characterized SKDH and AMP.     

The genetic control of grain esterases in hexaploid wheat

Summary A comparison of EST-5 grain esterase phenotypes from wheat-alien amphiploid, addition and substitution genotypes, resolved by flat-bed isoelectric focusing identified homoeologous Est-5 loci on chromosome 3H of Hordeum vulgare, 3H^ch of H. chilense, 3S^b of Aegilops bicornis, 3S¹ of Ae. sharonensis and Ae. longissima and 6R of Secale cereale and 6R^m of S. montanum. The Est-5 genes in alien species provide evidence for chromosome homoeology with wheat.     

Phylogenetic relationships of Triticum tauschii,the D genome donor to hexaploid wheat

Summary Isoelectric focusing of seed esterase (Est-5) isozymes in 79 T. tauschii accessions from diverse sources revealed the presence of six different seed esterase phenotypes. In one of these phenotypes, exclusive to a var. meyeri accession (AUS 18989), no detectable enzymatic activity was observed. Segregation in crosses between T. tauschii (D^t) accessions confirmed three of the seed esterase phenotypes to be alleles of the designated Est-D ^t5 gene locus; the inheritance pattern of these isozymes was not affected by the subspecies differences between the parents. On the bases of variation in Est-5 and their Glu-1 and Gli-1 gene loci (in a previous study in this series), only three strangulata accessions showed consistent homology with their prevalent gene expression in the D genome of hexaploid wheat. The implications of these observations for further interpreting the phyletic nature of the D genome donor in natural hexaploid wheat synthesis are also reported.