Genetic mapping of isozyme loci in Secale cereale L.

Summary The genetics and linkage relationships of several isozymatic and morphological markers have been investigated in different cultivars of rye (Secale cereale L.). The inheritance and the variability among cultivars of three new isozymatic zones are described: GOT2 and LAP, each of them under the control of a two-allele single locus, namely Got2 and Lap, respectively; and 6PGD1 controlled by two loci, 6Pgd1a and 6Pgd1b, which have alleles in common. Four linkage groups have been found: Acp2-Acp3, Got3-Mdh2-Lper4, Mdh1-6Pgd2-Pgi2, and Pgm-Eper2-[Eper1-Eper3]. The assignment of these four groups to the chromosomes 7R, 3R, 1R, and 4R is discussed.     

Mapping the nucleolus organizer region,seed protein loci and isozyme loci on chromosome 1R in rye

Summary The nucleolus organizer region located on the short arm of chromosome 1R of rye consists of a large cluster of genes that code for ribosomal RNA (designated the Nor-R1 locus). The genes in the cluster are separated by spacer regions which can vary in length in different rye lines. Differences in the spacer regions were scored in two families of F₂ progeny. Segregation also occurred, in one or both of the families, at two seed protein loci and at two isozyme loci also located on chromosome 1R. The seed protein loci were identified as the Sec 1 locus controlling -secalins located on the short arm of chromosome 1R and the Sec 3 locus controlling high-molecular-weight secalins located on the long arm of 1R. The two isozyme loci were the Gpi-R1 locus controlling glucose-phosphate isomerase isozymes and the Pgd 2 locus controlling phosphogluconate dehydrogenase isozymes. The data indicated linkage between all five loci and map distances were calculated. The results indicate a gene order: Pgd 2 ... Sec 3 ... [centromere] ... Nor-R1 ... Gpi-R1 ... Sec 1. Evidence was obtained that rye possesses a minor 5S RNA locus (chromosome location unknown) in addition to the major 5S RNA locus previously shown to be located on the short arm of chromosome 1R.     

Duplicated chromosome segments in maize (Zea mays L.): further evidence from hexokinase isozymes

Summary The genetic control of hexokinase isozymes (ATP: d-hexose-6-phosphotransferase, E.C. 2.7.7.1, HEX) in maize (Zea mays L.) was studied by starch gel electrophoresis. Genetic analysis of a large number of inbred lines and crosses indicates that the major isozymes observed are encoded by two nuclear loci, designated Hex1 and Hex2. Five active allozymes and one null variant are associated with Hex1, while Hex2 has nine active alleles in addition to a null variant. Alleles at both loci govern the presence of single bands, with no intragenic or intergenic heteromers visible, suggesting that maize HEX's are active as monomers. Organelle preparations demonstrate that the products of both loci are cytosolic. All alleles, including the nulls, segregate normally in crosses. Vigorous and fertile plants were synthesized that were homozygous for null alleles at both loci, suggesting that other hexosephosphorylating enzymes exist in maize that are undetected with our assay conditions. Linkage analyses and crosses with B-A translocation stocks place Hex1 on the short arm of chromosome 3, 27 centimorgans from Pgd2 (phosphogluconate dehydrogenase) and Hex2 on the long arm of chromosome 6, approximately 45 centimorgans from Pgd1. It is suggested that the parallel linkages among these two pairs of duplicated genes reflects an evolutionary history involving chromosome segment duplication or polyploidy.Paper No. 10170 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, NC     

Genetics of allozyme variation in Gossypium arboreum L. and Gossypium herbaceum L. (Malvaceae)

Summary Seed protein extracts from 90 accessions of Gossypium arboreum and 70 accessions of Gossypium herbaceum were electrophoretically analyzed for isozyme variation. Eighteen enzyme systems were resolved, ten of which were polymorphic among accessions. No within accession isozyme variation was observed within these highly inbred lines. A minimum of 24 genes encode the isozymes resolved and data is presented for codominant inheritance at 13 loci. Tests for non-random joint segregation in 63 of the 78 possible two-locus combinations from the 13 characterized loci give evidence for four pairs of linked genes (Lap2/Me1 [r=0.160+/-0.027], Lap2/Pgi1 [r= 0.285+/-0.055], Mdh6/Tpi1 [r= 0.197+/-0.028], and 6Pgd2/6Pgd3[r 0.000]. Numerous presumptive duplicate isozyme loci were observed and these were usually expressed as patterns of nonsegregating heteromultimers within accessions. Single gene expression was also observed at several loci. The observed results are in agreement with those of previous cytological investigations which have proposed the polyploid origin of the diploid Old World Gossypiums.     

Allozyme polymorphisms within and among open-pollinated and adapted exotic populations of maize

Summary Twelve U.S. Corn Belt open-pollinated and five adapted exotic populations of maize (Zea mays L.) were assayed for allozyme (allele) variation at 13 enzyme marker loci. Extensive allozyme variability was observed in all populations studied. No locus was monomorphic over all populations. Each of the lociIdh2, Got1, Mdh2, Pgd1, andPgd2 expressed two allozymes over all populations,Adh1, Acp1, Prx1, andEst1 each had three allozymes present,Est4, Glu1, andEnp1 had five allozymes, andAcp4 had six allozymes present. Significant deviations of genotypic frequencies were detected from Hardy-Weinberg equilibrium frequencies and 94% of average Fixation Index values indicated heterozygote deficiencies, which suggested that nonrandom mating and/or natural selection favoring homozygotes were possible factors affecting the maintenance or loss of genetic variability marked by these enzyme loci. Genetic distance and cluster analyses indicated that the observed genetic variability at the 13 enzyme loci was closely related to Dent and Flint types of maize.     

Genetics of α-amylases from rye endosperm

Summary Fifteen inbred lines of rye, F₁ and F₂ progenies from crosses between lines were studied using polyacrylamide gel electrophoresis. Conventional genetic analysis of -amylase zymograms showed that the 19 bands detected in the endosperm of germinating caryopses were controlled by three linked structural loci and one independent modifying locus, which influenced the electrophoretic mobility of isozymes. Two codominant alleles were found at the -Amy1, -Amy2 structural loci and the M--Amy modifying locus while the -Amy3 locus had three alleles. Double-banded expression of the -amylase alleles was probably due to the simultaneous presence of modified and unmodified forms of isozymes on the zymogram.This work was supported by Polish Academy of Sciences under project MR-II/7 and was also a part of the author's PhD Thesis     

Duplicate sequences with a similarity to expressed genes in the genome of Arabidopsis thaliana

The proportion of non-tandem duplicated loci detected by DNA hybridization and the segregation of RFLPs using 90 independent randomly isolated cDNA probes was estimated by segregation analysis to be 17%. The 14 cDNA probes showing duplicate loci in progeny derived from a cross between Arabidopsis-thaliana ecotypes Columbia x Landsberg erecta detected an average of 3.6 loci per probe (ranging from 2 to 6). The 50 loci detected with these 14 probes were arranged on a genetic map of 587 cM and assigned to the five A. Thaliana chromosomes. An additional duplicated locus was detected in progeny from a cross between Landsberg erecta x Niederzenz. The majority of duplicated loci were on different chromosomes, and when linkage between duplicate locus pairs was detected, these loci were always separated by at least 15 cM. When partial nucleotide sequence data were compared with GENBANK databases, the identities of 2 cDNA clones which recognized duplicate unlinked sequences in the A. Thaliana genome were determined to encode a chlorophyll a/b-binding protein and a beta-tubulin. Of the 8 loci carrying beta-tubulin genes 6 were placed on the genetic map. These results imply that gene duplication has been an important factor in the evolution of the Arabidopsis genome.     

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

Maize (Zea mays L.) cytosolic 6-phosphogluconate dehydrogenase isozymes (EC 1.1.1.44; 6-PGD) are encoded by unlinked lociPgd1 andPgd2. Two families from a Robertson's Mutator line were isolated which have no detectable expression ofPgd2. ThesePgd2-null mutants and aPgd1-null line were used to generate plants homozygous for null alleles at both cytosolic 6-PGD loci. The specific activity of 6-PGD in the double-null mutant was between 20 and 30% of wild-type levels in root extracts. The double-null mutant was reproductively viable in a moderate environment, suggesting that wild-type levels of cytosolic 6-PGD activity are not essential for growth. Isozyme dimer ratios in roots, leaves, and scutellum were binomial and reflected the wild-type gene copy number. 6-PGD isozymes showed tissue- and cell type-specific expression. This research was supported by grants from the United States Department of Agriculture (Individual Postdoctoral Grant 89-37264-4837 to J.B.-S.) and the National Institutes of Health (Postdoctoral Grant 5-F32-GM11112-03 to J.B.-S. and Research Grant 2-R01-GM21734 to M.F.).     

Isolation and characterization of polymorphic microsatellite loci from a dinucleotide-enriched genomic library of spotted maigre (Nibea albiflora)

In the present study, we reported 13 polymorphic microsatellite loci isolated from a dinucleotide-enriched genomic library of Nibea albiflora. The number of alleles, observed and expected heterozygosity per locus in 44 individuals ranged from 2 to 13, from 0.0909 to 0.9773 and from 0.0886 to 0.9073, respectively. Three loci significantly deviated from Hardy–Weinberg equilibrium after Bonferroni correction. Analysis of linkage disequilibrium showed non-significant among the two pairs of loci. As a result, 13 microsatellite loci probably located on different chromosome pairs and these polymorphic microsatellite loci should provide sufficient level of genetic diversity to investigate the fine-scale population structure and evaluate the breeding strategy in Nibea albiflora. Shichao Xing, Changwei Shao contributed equally to this work.     

A Nested Alpha-Amylase Gene in <Emphasis Type="Italic">Drosophila ananassae</Emphasis>

The amylase gene family of Drosophila ananassae consists in seven copies, scattered on several chromosomal arms. We have evidenced that a member of the family, Amy35, lies within an intron of a gene homologous to the CG14696 gene of D. melanogaster. This nested arrangement seems restricted to the D. ananassae subgroup. The nested and the nest genes are encoded on opposite strands. Both are actively transcribed in the midgut at the same time, raising the possibility of interference between their mRNAs. Our data also help to elucidate the history of the Amy family, suggesting that Amy35 arose by duplication and translocation from another ancestral locus, into a formerly short intron, in an ancestor of the subgroup.     

Development of Novel Microsatellite DNA Markers from the Pacific Oyster Crassostrea gigas

We document the potential of novel microsatellites as a genetic tool in furthering our understanding of the Crassostrea gigas genetic structure. From the microsatellite-enriched libraries we constructed, 123 repeat regions that had sufficient sequence information to design polymerase chain reaction primer sets were isolated. From these, 9 primer pairs were screened in a C. gigas population of 67 individuals to evaluate the genetic variability. All but 1 of the 9 loci showed allelic variation (number of alleles, 2–20; observed heterozygosity, 0.119–0.925; unbiased expected heterozygosity, 0.139–0.914). Considerable discrepancy of genotypic proportions from the Hardy-Weinberg equilibrium was observed at 1 locus with an apparent heterozygote deficiency. Several loci were successfully amplified in 3 other related species with the appropriate allele size: 6 loci in C. sikamea, 4 loci in C. ariakensis, and 5 loci in C. nippona.     

Genetic Variation and Differentiation among Populations of Chum Salmon Oncorhynchus ketaWalbaum from Southern Russian Far East

Allozyme variation of populations of chum salmon Oncorhynchus ketafrom southern Russian Far East was examined. Of 55 loci screened, 31 were polymorphic. Within-population variation accounted for most of the allele diversity; F _STaveraged over loci was 0.052. Linkage disequilibrium was found in less than 5% of locus pairs in the chum population examined. Analysis of within- and among-population variance components of linkage disequilibrium using D-statistics (Ohta, 1982) showed that most genetic variation was distributed among populations.     

Isolation and characterization of novel polymorphic nuclear microsatellite markers from Ophrys fusca (Orchidaceae) and cross-species amplification

The present study reports the isolation and characterization of eight new polymorphic microsatellite loci from the sexually deceptive orchid Ophrys fusca. Microsatellites were isolated from two partially enriched genomic libraries using FIASCO (Fast Isolation by AFLP of Sequences COntaining repeats). Seventy-three loci were screened for primer design and primer pairs corresponding to eight different loci were selected for microsatellite characterization of two Portuguese populations. Total number of alleles per locus ranged from 10 to 32. All loci showed a high level of observed heterozygosity (H₀) ranging from 0.33 to 1 and were possible to amplify in 16 other species of Ophrys using the same primers. H. C. Cotrim and F. A. Monteiro have contributed equally to this work.     

Genetic studies of mutations at two loci of Drosophila melanogaster which cause a wide variety of homeotic transformations

Summary The ash-1 locus is in the proximal region of the left arm of the third chromosome of Drosophila melanogaster and the ash-2 locus is in the distal region of the right arm of the third chromosome. Mutations at either locus can cause homeotic transformations of the antenna to leg, proboscis to leg and/or antenna, dorsal prothorax to wing, first and third leg to second leg, haltere to wing, and genitalia to leg and/or antenna. Mutations at the ash-1 locus cause, in addition, transformations of the posterior wing and second leg to anterior wing and second leg, respectively. A similar spectrum of transformations is caused by mutations at yet another third chromosome locus, trithorax. One extraordinary aspect of mutations at all three of these loci is that they cause such a wide variety of transformations. For mutations at both of the loci that we have studied the expression of the homeotic phenotype is both disc-autonomous (as shown by injecting mutant discs into metamorphosing larvae) and cell autonomous (as shown by somatic recombination analysis). The original mutations which identified these two loci, although lethal, manifest variable expressivity and incomplete penetrance of the homeotic phenotype suggesting that they are hypomorphic. The phenotype of double mutants which were synthesized by combining different pairs of those original mutations manifest for two of the four pairs a greater degree of expressivity and slightly more penetrance of the homeotic transformations. This mutual enhancement suggests that the products of both loci interact in the same process. A third double mutant expresses a discless phenotype.Additional alleles have been recovered at both the ash-1 and the ash-2 loci. Some of these alleles as homozygotes or transheterozygotes express the wide range of transformations revealed first by double mutants. One of the alleles at the ash-1 locus when homozygous and several transheterozygous pairs can cause either the homeotic transformation of discs or the absence of those discs. The fact that these two defects, absence of specific discs and homeotic transformations of those same discs can be caused by mutations within a single gene suggests that the activity of the product of this gene is essential for normal imaginal disc cell proliferation. Loss of that activity leads to the absence of discs, whereas, reduction of that activity leads to homeotic transformations.     

Development and characterization of 13 novel microsatellite loci from the flat-headed bat (Tylonycteris pachypus) with cross-species amplification in closely related taxa

13 novel microsatellite loci was isolated using the enriched library method from genomic DNA of the flat-headed bat (Tylonycteris pachypus). These loci showed high levels of genetic polymorphism testing on 54 individuals sampled from Guangxi province, China. The number of observed alleles per locus ranged from 2 to 15. The expected and observed heterozygosity values ranged from 0.170 to 0.900 and from 0.185 to 0.944, respectively. One loci departed significantly from Hardy-Weinberg equilibrium (HWE) after Bonferroni correction and no Linkage disequilibrium was found between any pairs of loci. In addition, these loci were tested in the sister species, Tylonycteris robustula, seven loci amplified successfully and were also polymorphic.     

天麻基因组微卫星特征分析与分子标记开发

该研究基于第二代测序技术建立了天麻的基因文库,筛选微卫星序列,并对微卫星位点的类型、丰度、长度、偏好性等进行了分析与比较;并为60条重复次数高的微卫星序列设计了引物,运用4个种群80个样本进行了PCR扩增和聚丙烯酰胺凝胶电泳检测。结果表明:(1)天麻基因组测序得到61 048条基因序列,检测出微卫星位点12 107个,其中二核苷酸重复最多、长度变异大。(2)设计的60对微卫星引物中的20对能扩增出清晰条带且有多态性,每个位点的复等位基因数(N_a)在4~14之间,平均为8.40;多态性信息含量(PIC)平均为0.77。该研究开发的天麻微卫星分子标记为开展天麻遗传学研究及种质资源鉴定等工作奠定了基础。     

Isolation and characterization of polymorphic microsatellite loci from a dinucleotide-enriched genomic library of seven-band grouper (Epinephelus septemfasciatus) and cross-species amplification

Seven-band grouper (Epinephelus septemfasciatus) is a commercially important fishery species. Sixty-six microsatellite loci were isolated from a dinucleotide-enriched genomic library of E. septemfasciatus. Twelve of these loci were polymorphic in a test population with alleles per locus ranging from two to five, and observed and expected heterozygosities per locus from 0.04 to 1.00 and from 0.28 to 0.76, respectively. Three loci significantly deviated from Hardy–Weinberg equilibrium and no significant linkage disequilibrium was found between pairs of loci after Bonferroni correction. Cross-species amplification of these polymorphic microsatellite loci was performed in additional two related species. These polymorphic microsatellite loci would be useful for investigating genetic resource of E. septemfasciatus and other related species. Lili Zhao and Changwei Shao have contributed equally.     

Inheritance of enzymes and blood proteins in the leopard frog,Rana pipiens: Three linkage groups established

Individuals from natural populations of the leopard frog, Rana pipiens, were analyzed for electrophoretic differences in blood proteins and enzymes from an amputated digit. The proteins examined represent products of 72 loci. Presumptive heterozygotes at multiple loci were selected for experimental crosses. Mendelian inheritance of 18 protein variations were demonstrated in the offspring. Tests for linkage or independent assortment were performed for 75 locus pairs. Three linkage groups were established. Linkage group 1 contains two loci, aconitase-1 (Acon1) and serum albumin (Alb), with a 19% recombination frequency between them. Linkage group 2 contains four loci, glyoxalase (Gly), acid phosphatase-1 (Ap1), acid phosphatase-2 (AP2), and esterase-5 (Est5). The data show the relationships Gly-21.1%-AP1-0%-AP2-6.3%-Est5, and Gly-25.6%-Est5. Linkage group 3 consists of four closely linked esterase loci. The data, Est1-5.1%-Est6, Est6-1.8%-Est10-1.9%-Est4 and Est6-3.0%-Est4, do not establish a complete order but suggest that Est10 is between Est4 and Est6. These results, with data demonstrating apparent independent assortment of 67 other locus pairs, provide a foundation for establishing the frog genetic map.The project was supported by Grant No. RR-00572 from the Division of Research Resources, National Institutes of Health. This paper is contribution No. C-87 from the Amphibian Facility, George W. Nace, Director.     

Twelve polymorphic microsatellite loci from a dinucleotide-enriched genomic library of Japanese Spanish mackerel (Scomberomorus niphonius)

In the study, 34 microsatellite loci were isolated from a dinucleotide-enriched genomic library of Japanese Spanish mackerel (Scomberomorus niphonius). And 12 microsatellite loci were found to be polymorphic between 3 and 8 alleles. The number of observed and expected heterozygosity per locus in 23 individuals ranged from 0.6087 to 1.0000 and 0.8908 to 0.9773, respectively. Two loci significantly deviated from Hardy–Weinberg equilibrium after Bonferroni correction analysis and there was no significant linkage disequilibrium found between pairs of loci. As a result, 12 microsatellite loci probably located on different chromosome pairs and these polymorphic microsatellite loci should provide sufficient level of genetic diversity to investigate the fine-scale population structure and evaluate the breeding strategy in S. niphonius. The authors Shi-Chao Xing and Gen-Bo Xu contributed equally.     

Isolation and characterization of microsatellite loci in <Emphasis Type="Italic">Melicope quadrilocularis</Emphasis> (Rutaceae), an endemic plant species of the Bonin Islands,Japan, and cross-species amplification in closely related taxa

Twelve microsatellite loci were isolated and characterized for Melicope quadrilocularis, an insular endemic tree species of the Bonin Islands. The observed number of alleles at each locus ranged from 1 to 18. The range of expected heterozygosity was 0.0000–0.9445. The inter-specific applicability of these loci was evaluated by analyzing two other endemic species and one endemic variety of Melicope that are also distributed on the Bonin Islands. All primer pairs for the 12 loci tested successfully amplified the loci in all taxa, except for primers for four loci in M. nishimurae.