Leucine Aminopeptidase Locus Research Articles

Size-dependent, spatial and temporal genetic variation at a leucine aminopeptidase (LAP) locus among blue mussel ( Mytilus galloprovincialis ) populations along a salinity gradient

Biochemical genetic variation at a leucine aminopeptidase (LAP) locus is related to salinity variation in several marine bivalve molluscs. This paper details an investigation of the Long Island Sound model of LAP selection (LAP genotype-dependent mortality occurring among newly settled Mytilus edulis mussels) carried out in 1997 among three M. galloprovincialis mussel populations along the salinity gradient of Wellington Harbour, New Zealand. Significant LAP genotypic heterogeneity was observed at the LAP locus between small ( 25 mm shell length) M. galloprovincialis from Petone and Eastbourne (the two sites experiencing the greatest salinity variation), whereas genotypic heterogeneity was not significantly different between small and large mussels from Seatoun (the site experiencing the least salinity variation). The Lap3 allele decreased in frequency and the Lap4 allele increased in frequency at Petone and Eastbourne, whereas the Lap3 and Lap4 allele frequencies remained effectively constant at Seatoun. Both these findings are consistent with the Long Island Sound model of selection. At all three locations, the Lap3,3 genotype decreased in frequency from small to large mussels, whereas the Lap3,4 genotype increased in frequency from small to large mussels. All other LAP genotypes occurred at low frequencies (<0.10) at all three locations and showed no evidence of frequency change from small to large-size mussels nor evidence of clinal change among the three locations. These genotype frequency data possibly indicate that the Lap3,3 genotype is at a selective disadvantage compared to the Lap3,4 genotype at all three locations, and that this selective disadvantage is related to the extent of salinity variation which exists at each location. Further investigation is required before it can be determined if the Long Island Sound model of selection best describes the size-dependent and location-specific changes in LAP allele and genotype frequencies along this salinity gradient. Comparison of the population genetic structure at the LAP locus in 1995 and in 1997 revealed a profound change from heterozygote excesses to heterozygote deficiencies for all three M. galloprovincialis populations. The reason for the change is unknown, but the change indicates that population genetic structure at the LAP locus is highly variable in time, but consistent in space, among these M.␣galloprovincialis populations.

Biochemical genetic variation at a leucine aminopeptidase (LAP) locus in blue ( Mytilus galloprovincialis ) and greenshell ( Perna canaliculus ) mussel populations along a salinity gradient

In several marine bivalve species, biochemical genetic variation at a leucine aminopeptidase (LAP) locus is associated with environmental variability, primarily salinity fluctuation. Population genetic variation at a LAP locus was investigated here in two sympatric mussel species (Mytilus galloprovincialis and Perna canaliculus) from three locations along a salinity gradient in Wellington Harbour, New Zealand. The data for M. galloprovincialis and P. canaliculus do not support the hypothesis that the LAP polymorphism in either species is associated with salinity variation among adult mussels. Due to the absence of small mussels among the samples it is not possible to discount the hypothesis that selection acts primarily against juveniles, as it does for M. edulis in Long Island Sound, USA. Wellington Harbour populations of M. galloprovincialis exhibited large and often highly significant heterozygote excesses at the LAP locus, whereas populations of P. canaliculus from the same locations exhibited large and highly significant heterozygote deficiencies. The reason for this inter-specific difference in population structure is unknown. If it is the result of selection, this suggests that selection acts differentially upon the two species, because demographic attributes and reproductive biology are very similar in the two species. For both M. galloprovincialis and P. canaliculus, significant levels of population genetic heterogeneity were recorded among three locations separated by only 8 to 12 km. Neither species exhibited shell length-dependent genetic variation at the LAP locus, suggesting that for these two species the LAP polymorphism is not associated with variation in shell length.

Uniform variation in genetic traits of a marine bivalve related to starvation, pollution and geographic clines

Consistent patterns of genetic variation in the marine bivalve Macoma balthica (L.) were found after exposure to low levels of copper, starvation, and along geographic clines. The geographic clines were related to temperature and salinity. Genetic differences were primarily found in the LAP (Leucine aminopeptidase) locus; under stress the frequency of one specific allele, and thereby the heterozygosity, decreased strongly. The degree of changes depended on age and condition of the animals; adult animals showing stronger changes than juveniles. Low concentrations of copper yielded stronger genetic changes than high concentrations. It is concluded that genetic diversity and stress-sensitivity of species change predictably along a gradient in response to environmental harshness. Animals near the southern limit of their range were more sensitive to additional stress.

Genetic linkage of a leucine aminopeptidase locus with the Kunitz trypsin inhibitor locus in soybeans.

The soybean (Glycine max (L.) Merrill) seed leucine aminopeptidase locus (Lap1) was found to be linked to the Kunitz trypsin inhibitor locus (Ti) with a recombination frequency of 15.3 percent +/- 0.9 percent. The two loci are in linkage group 9. Both Lap1 and Ti loci are inherited independently of the flower color locus (W1) in linkage group 8.

Genetic Linkage of Biochemical and Morphological Traits in Soybean1

Biochemical and morphological markers were used to study linkage relationships in soybean [Glycine max (L.) Merr.]. Pubescence color locus (t) and the ß‐amylase locus (Am3) are linked with 31.88%±2.02% recombination frequency. They are in Linkage Group 1. Pubescence color locus is unlinked with diaphorase locus (Dial), isocitrate dehydrogenase loci (Idh1, Idh2) and leucine aminopeptidase locus (Lap1). Pod color locus (l2) segregates independently of Am3, Dia2, Idh1, Idh2, Lap1, and Pgm1 loci. No linkage relationship was found between any pair of the enzyme loci studied.

Distribution of homoeoalleles at two loci in a diploidized tetraploid: leucine aminopeptidase loci in Avena barbata

Distribution of homoeoalleles at two loci in a diploidized tetraploid: leucine aminopeptidase loci in Avena barbata

Loss of duplicate gene expression in tetraploid Chenopodium

Genetic analyses indicate that single-banded leucine aminopeptidase (LAP) phenotypes in tetraploid Chenopodium reflect homozygosity for null alleles at either locus of a polyduplicated pair. Other duplicated isozyme loci show simplification to the diploid phenotype. Loss of duplicate gene expression in the LAP system has occurred independently in putatively specialized taxa occupying the distributional periphery of a New World tetraploid complex. The geographic/taxonomic pattern of genetic variation suggests that fixation of null alleles is mediated by stochastic genetic phenomena associated with migration. Plants homozygous for null alleles at both LAP loci show no detetable activity in assays involving several exopeptidase substrates, although growth and fertility of double-null plants are not markedly reduced. Our data confirm that loss of duplicate gene expression can occur in isozyme systems of polyploid plant taxa. Thus, lack of electrophoretically detectable duplicate gene expression is not a certain indication of diploidy. However, loss of duplicate gene expression in population systems known to be of allopolyploid origin is a clear indication of phyletic derivation.

Geographic variation in allele frequencies at three loci in Chlamys opercularis from Norway to the Brittany coast

Geographic variation of allele frequencies at four loci in Chlamys opercularis was investigated using electrophoresis on polyacrylamide gels. Large differences were observed between populations at a protein locus, while some small but significant variations occurred at the phosphoglucomutase-2 and octopine dehydrogenase loci. The leucine aminopeptidase locus appeared monomorphic. On the basis of mean genetic identities derived from three loci in nine populations and hydrographic data on coastal current systems, it is proposed that there are at least four relatively genetically isolated populations of this scallop around the British Isles, namely (1) North and West Scottish coast, (2) the Irish Sea, (3) the Celtic Sea (Brittany coast) and (4) the English Channel. It is argued that both random genetic drift and selection may play a significant part in the establishment and retention of large allele frequency differences between isolated populations of this species.

Genetic Variation among South American Populations of Tetraploid Chenopodium sect. Chenopodium subsect. Cellulata

Electrophoretic analysis of South American Chenopodium (sect. Che- nopodium subsect. Cellulata, 2n = 4x = 36) reveals multi-locus isozyme systems for leucine aminopeptidase (LAP) and phosphoglucoisomerase (PGI) that appear to be the result of tetraploid gene duplication. The bi-locus LAP system is monomorphic for active alleles with putative null alleles at each locus that are not present in pop- ulations at the northern range extreme. The null allele at Lap-i appears to be sporadically distributed in the highlands of Peru, Bolivia, and Argentina, whereas the null variant at Lap-2 shows a clinal increase from north to south with fixation in the Argentine lowlands. All material (62 population samples from Chile, Argen- tina, Bolivia, and Peru, and 206 exemplar samples from Ecuador, Peru, and Bolivia) is monomorphic at Pg'-I and essentially monomorphic at the other two PGI loci, with the exception of low elevation populations of Argentina, which show five active variants and one null. Aside from clinal trends at two loci, the observed pattern of genetic variation is not consistent with extreme discontinuities in selective regime, habitat, and distribution. It is proposed that an archaic genotype has been conserved in the Andean area of chenopod cultivation through interpopulation gene flow me- diated by weed-crop genetic interaction and human dispersal. A relatively high level of inter-population reproductive isolation in lowland Argentina has possibly allowed differentiation of PGI alleles and silencing of one LAP locus through fixation of null alleles. Populations from lowland Argentina include individuals showing electro- phoretic diploidization in both isozyme systems, thus producing the typical pheno- type of diploid Chenopodium. The percentage of heterozygous plants per population and level of detected out-crossing indicate a high potential for gene flow within populations of lowland Argentina, although genetic interaction with sympatric C. album was not detected.

Enzyme variability in natural populations of Daphnia carinata king

Fifteen populations of the cladoceran crustacean, Daphnia carinata, were examined for allozyme variation at sixteen gene loci. Individuals of this cyclic parthenogen were heterozygous at only 2.1 per cent of their loci. Large differences in gene frequencies existed among the populations. Within populations genotypic frequencies were in good agreement with Hardy-Weinberg expectations, and remained stable during annual cycles of population growth. Strong linkage disequilibrium was observed between the allelic variants at two leucine aminopeptidase loci in certain populations, suggesting that the loci are tightly linked and that populations of D. carinata are founded from few individuals.

Gene frequency changes and adaptation in marine cockles

When closely related species overlap geographically, a change of character state may occur in one species which is directly attributable to the presence in the same environment of an ecologically similar species1,2. Most reports of this phenomenon—called character displacement—have been concerned with divergence, rather than convergence, in morphologial characters between species in the zone of sympatry. There has been only one report on genetic displacement at the allelic level3. In this, Murphy observed a divergence in allele frequency at a leucine aminopeptidase locus in sympatric species of marine limpets which he interpreted as allelic accommodation in response to interspecific competition3. I report here a study of two closely related species of cockles, Cerastoderma edule and Cerastoderma glaucum, in which C. glaucum exhibits a convergence in allele frequency at the phosphoglucomutase (Pgm) locus when it is found intermixed with C. edule.

Protein Polymorphism and Genetic Variation in a Population of the Japanese Quail

To evaluate genetic variation in a quail population, 17 enzymes and proteins were examined by the use of starch gel electrophoresis. Of the 24 loci examined 10 were shown to be polymorphic; one of three mannose phosphate isomerase loci, glutamate DH locus, sorbitol DH locus, malic enzyme-I locus, acid phosphatase locus, alcohol DH locus, amylase locus, one of three hemoglobin loci, ovalbumin locus and esterase D locus. Other 14 loci defined as monomorphic included two mannose phosphate isomerase loci, malic enzyme-II locus, phosphoglucomutase locus, two aspartate aminotransferase loci, alpha-glycerol phosphate DH locus, two malate DH loci, muscle lactate DH locus, leucine aminopeptidase locus, two hemoglobin, loci and albumin locus. Using both the data presently obtained and our published data on 6 polymorphic loci (catalase locus, liver esterase locus, brain esterase-II locus, phosphoglucose isomerase locus, 6-phosphogluconate DH locus and transferrin locus) and a monomorphic locus (brain esterase-III locus), proportion of polymorphic loci (Ppoly), mean heterozygosity per individual (H) and effective munber of alleles per locus (ne) were calculated. The estimated Ppoly, H and ne were 0.516, 0.167 and 1.20, respectively.

TEMPORAL PATTERNS OF ALLOZYMIC VARIATION IN FLUCTUATING POPULATIONS OF MICROTUS OCHROGASTER.

Microtine rodents undergo 2-4 year fluctuations in population density known as population cycles. A genetic-behavioral mechanism that is based on an rand Kselection argument has been proposed by Chitty (1960, 1967) for controlling these cycles. During the phase of increasing numbers when mutual interference is minimal, genotypes with a high reproductive effort have a selective advantage, whereas during the peak phase when mutual interference is intensive, there is selection for aggressive behavior. Although aggressive genotypes have an advantage with respect to intraspecific competition for food and space, their fitness is reduced in other ways which sets the stage for the decline phase. Thus, Chitty's hypothesis assumes that natural selection coupled with changes in the genetic composition of the population is the driving force behind population cycles. The results from studies monitoring allozymic variation in fluctuating vole populations are compatible with Chitty's hypothesis. Semeonoff and Robertson (1968) observed changes in gene frequency at a plasma esterase locus in a declining population of Microtus agrestis. Canham (1969) found that heterozygote fitness at transferrin and albumin loci was correlated with density in Peromyscus maniculatus and Clethrionomys gapperi populations. Changes in gene frequency at transferrin (Tamarin and Krebs, 1969) and leucine aminopeptidase loci (Gaines and Krebs, 1971) were correlated with

COLLISELLA AUSTRODIGITALISSP. NOV.: A SIBLING SPECIES OF LIMPET (ACMAEIDAE) DISCOVERED BY ELECTROPHORESIS

A geographic survey of protein polymorphism in the intertidal limpet Collisella digitalis reveals that populations from northern California and Oregon have allelic frequencies at a leucine aminopeptidase locus that are sufficiently different from populations in southern California that individuals can be correctly assigned to their geographic entity with a 98.8% probability on the basis of their genotype. These two groups also have different allelic frequencies at a phosphoglucose isomerase locus, but only slight morphological differences between the groups are evident.Genotype frequency analysis shows that on the central California coast between Monterey Bay and Point Conception both the northern and southern groups are present, but not interbreeding. Thus, these groups are sibling species. The southern species is herein named Collisella austrodigitalis sp. nov.These species are thought to have originated by allopatric speciation, perhaps following the spatial isolation of a population of C. austrodigitalis during an equatorward contraction of that species' range in response to one of the late Cenozoic world wide cooling trends.

Biochemical relationships of the Holarctic vole genera (Clethrionomys, Microtus, and Arvicola (Rodentia: Arvicolinae))

Transferrin (Tf), hemoglobin (Hgb), leucine aminopeptidase (LAP), 6-phosphogluconate dehydrogenase (6PGH), and glucose-6-phosphate dehydrogenase (G6PD) were examined by starch-gel electrophoresis in Holarctic Microtus oeconomus and Clethrionomys rutilus, Siberian Microtus hyperboreus and Clethrionomys rufocanus, and North American Microtus miurus, Microtus ochrogaster, Microtus pennsylvanicus, Arvicola richardsoni, and Clethrionomys gapperi. Thirty alleles of five to seven loci, the number depending on the presence or absence of one or two minor hemoglobin fractions, were identified in these species. Interspecific comparisons were based on the presence of at least one allele shared in common at the various loci. The closest biochemical resemblances occurred between populations of Holarctic M. oeconomus and C. rutilus. Clethrionomys gapperi and C. rutilus were quite similar but C. rufocanus was divergent. Observed resemblances between M. hyperboreus and M. miurus were not strong and do not support the inclusion of the former in the amphiberingian narrow-skulled vole group. Arvicola richardsoni, though seemingly close to M. pennsylvanicus, was quite divergent from all other species of Microtus at the LAP locus and warrants comparison with Palearctic Arvicola. Microtus ochrogaster and M. pennsylvanicus shared many similarities and served as reference samples.

マガキの生化学的遺伝多型-III

Genetic variations have previously been described in the myogen, est erases, tetrazolium oxidase, and leucine arninopeptidases in the Pacific oyster, Crassostrea gigas. Some 900 specimens (35 lots) of the Pacific oyster, sampled from the wild populations off the Pacific and the Japan Sea coasts of Hokkaido, and off Iwate and Akita Prefectures, as well as from the cultured populations from Miyagi and Hiroshima Prefectures, were compared for gene frequencies at the loci noted above. No significant geographical difference was seen in esterases and tetrazolium oxidase. At the leucine aminopeptidase locus, frequencies of the allele Lap5 increased towards the lower latitudes along the Pacific coast, indicating a marked difference between Ryori and Ofunato, Iwate Prefecture. This resulted in a distinction of the arbitrarily named “Hokkaido-northern Tohoku and southern Tohoku groups”. Two dimensional comparisons with the allele M2 (myogen) and Lap5 made possible the distinction of the cultured population in Hiroshima from the two wild populations noted above. Overdominance of the heterozygote 5•7 at the Lap locus was observed both in the wild and cultured populations sampled. Zymograms of the “unidentified specimens” reported before were identical to those of C. nippona SEKI, sampled from Akita Prefecture. Some future studies are suggested towards solutions of problems or questions raised from the discussions of the present study.

POPULATION GENETICS OF MARINE PELECYPODS. IV. SELECTION, MIGRATION AND GENETIC DIFFERENTIATION IN THE BLUE MUSSEL MYTILUS EDULIS.

Mytilus edulis is a prominent and widely distributed littoral mussel, whose life cycle is typical of intertidal marine invertebrates with an extended larval dispersal period and sedentary adulthood. The larvae appear capable of moving great distances. The present study is an attempt to begin the characterization of the genetic structure of this important species in both its static and dynamic aspects. The distributions of alleles and genotypes over a broad, environmentally diverse geographic range have been determined by electrophoretic analysis, and the possible contributions of selection and migration to these distributions have been investigated. As a result, we here report in detail a number of observations, including the following: the uniformity of genotypic frequencies over large portions of the species range; abrupt and gradual genotypic transitions over great, moderate and very small distances; certain discordances among patterns of variation of different loci; a widespread and striking deficiency of heterozygotes at two loci; and clear evidence of the local selection of certain genotypes at the Leucine aminopeptidase locus. We have sought to interpret our observations in terms of the classical influences on the structure of genetic variation: nonrandom mating, selection, and migration. Given the spawning behavior of mussels. any non-random mating is likely to be inbreeding. Selection might in some cases favor certain alleles or genotypes (heterozygotes, for example) over the entire species range. In other cases, the direction and intensity of selection might vary with habitat, creating a tendency towards genetic differentiation of the species. Dispersal would of course have the cumulative tendency to make the species more uniform, but there could be two characteristic shortterm effects in addition. First, in each generation a deficiency, or less likely, an excess (Li, 1969; Milkman, 1975) of heterozygotes could result from the mixing of individuals from genetically different populations; this deficiency or excess would of course last only for the generation in which it appeared, and another mixing would be required for a similar deviation in the next generation. A second short-term effect is linkage disequilibrium, which (unlike a deviant frequency of heterozygotes) dissipates with first-order kinetics and therefore takes a number of generations, depending on recombination frequency, to become indistinct. When the genotypic frequencies at a polymorphic locus are similar throughout a particular range, then, we can conclude that cumulative dispersal (together with any selection that operates uniformly) is sufficient to counterbalance inbreeding (together with any selection that operates non-uniformly). A deficiency or excess of heterozygotes can indicate selection or dispersal within the period of one life cycle. Linkage disequilibrium can indicate selection or dispersal within the period of a few life cycles. A variety of genetic differences, over distances and times of any magnitude, can be attributed to selection. While 1 This paper is dedicated to the memory of Prof. Ove Frydenberg. 2 Department of Ecology and Evolution, State University of New York, Stony Brook, New York 11794. 'Department of Zoology, University of Iowa, Iowa City, Iowa 52242. 'Present Address: Department of Biology-EPO, University of Colorado, Boulder, Colorado 80302.

An analysis of selection at two loci in fluctuating populations of Microtus.

Indirect estimates of differential early mortality at the transferrin (Tf) and leucine amino-peptidase (LAP) loci in fluctuating populations of Microtus pennsylvanicus have been obtained. Among individuals first captured during decline phases, there were consistent excesses of males heterozygous at the Tf locus. Among individuals first captured during increase phases, there were consistent excesses of males heterozygous at the LAP locus. It is concluded that these observations are attributable to selection.

Genetische Untersuchungen bei Picea abies mit Hilfe der Isoenzym-Identifizierung

Using techniques of starch gel zone electrophoresis, a considerable variation among esterase and leucine aminopeptidase isoenzyme patterns was found in the endosperm of dormant seeds of Norway spruce (Picea abies). Since the so-called primary endosperm of conifers is only a further developmental stage of the haploid female gametophyte, simple Mendelian segregations can be determined in seeds of individual open-pollinated trees. It was therefore possible to identify some esterase and leucine aminopeptidase loci only with regard to phenotypic frequency distributions without difficult crossing procedures.

An analysis of polymorphisms among isozyme loci in dark and light Drosophila ananassae strains from American and Western Samoa.

There is mounting evidence that Drosophila populations are mlore polymorphic at the level of genetic loci than was formerly thought by many geneticists. There have been many experimental demonstrations of the extensive chromosomal polymorphis^ms, of the presence of considerable quantities of hidden deleterious and lethal alleles in the populations, and of the extensive complexity of the coadapted genetic systems integrated through natural selection.' Nevertheless, the proportion of polymorphisms among the majority of all loci is largely unknown because of inadequate screening techniques. Furthermore, the mechanisms for the maintenance of polymorphisms -remain elusive to experimental verification. The ideal situation of screening populations for genetic comparisons at and between individual loci has been brought a step closer to reality by electrophoretic separation of enzyme molecules. Though enzyme differences are not necessarily related with genetic differences on a one-to-one basis, most may be. At any rate, zymogram analysis of individual flies for electrophoretic mobility or qualitative activity differences gives a good first approximation of the underlying genetic situation for a different class of variation than has previously been studied directly. However, as Lewontin and Hubby3 have pointed out, the randomness of the samples of loci studied by this technique is critical for broader generalizations which might be made from the findings in this class of loci. Sample characteristics are yet to be determined. Lewontin and Hubby3 have found about 40 per cent of all electrophoretically separable enzyme systems and protein bands of no known enzymatic activity of D. pseudoobscura to be polymorphic, having two or more electrophoretic forms of the same protein. One expects the difference in molecular forms to represent at least as much genetic difference, so that the variation of molecular types reflects similar variation of genotypes. If only a moderate bias is involved in estimating this proportion for the genome, then there exists a major discrepancy between the data and the expectation based upon the theory of segregational load. According to the theory, a population may bear, without being jeopardized by reduced average fitness, only a relatively small portion of loci in heterotic polymorphic conditions. In order to establish the meaning of the apparent inconsistency between the theory and observations, it must be established whether or not these isozyme polymorphisms are maintained more or less independently by some form of selection. It is very important to know if these variations are random representatives of a large number of such loci. It has been demonstrated in a laboratory population of D. busckii4 that the polymorphism at the leucine aminopeptidase locus is maintained by heterotic selection, though this was not the case for an esterase locus in D. inelanogaster and D. simulans.5