Comparative Genome Mapping of the Ataxia–Telangiectasia Region in Mouse, Rat, and Syrian Hamster

Chromosomal locations of theAtm(ataxia–telangiectasia (AT)-mutated) andAcat1(mitochondrial acetoacetyl-CoA thiolase) genes in mouse, rat, and Syrian hamster were determined by direct R-banding FISH. Both genes were colocalized to the C-D band of mouse chromosome 9, the proximal end of q24.1 of rat chromosome 8, and qa4–qa5 of Syrian hamster chromosome 12. The regions in the mouse and rat were homologous to human chromosome 11q. Fine genetic linkage mapping of the mouse AT region was performed using the interspecific backcross mice.Atm, Acat1,andNpat,which is a new gene isolated from the AT region, and 12 flanking microsatellite DNA markers were examined. No recombinations were found among theAtm, Npat, Acat1,andD9Mit6loci, and these loci were mapped 2.0 cM distal toD9Mit99and 1.3 cM proximal toD9Mit102.Comparison of the linkage map of mouse chromosome 9 (MMU9) and that of human chromosome 11 (HSA11) indicates that there is a chromosomal rearrangement due to an inversion betweenEts1andAtm–Npat–Acat1and that the inversion of MMU9 originated from the chromosomal breakage at the boundary betweenGria4andAtm–Npat–Acat1on HSA11. This type of inversion appeared to be conserved in the three rodent species, mouse, rat, and Syrian hamster, using additional comparative mapping data with theRckgene.     

Mapping of the MouseLy-6, Xp-14, andGdc-1 loci to chromosome 15

TheLy-6 locus is now regarded as a gene complex consisting of at least five closely linked loci (Ly-6A-Ly-6E) whose polymorphic products are identified by monoclonal antibodies and distinguished by different tissue distributions.Ly-6 has been assigned by other investigators to chromosome (Chr) 9 (linked toThy-1 or to Chr 2. We report that theLy-6 gene complex, together with theXp-14 andGdc -1 loci, is situated on Chr 15 linked toGpt1. These new linkage data are derived from four sources: (1) three separate crosses that failed to demonstrate linkage ofLy-6 to eitherThy-4 on Chr 9 or to any of five genes present on Chr 2; (2) the NXSM recombinant inbred strains, which suggested the linkage ofLy-6 andXp-14 toGpt-1 on Chr 15; (3) severalGpt-1 andGdc-1 congenic strains that confirmed the assignment ofLy-6 andXp-14 to Chr 15; and (4) backcrosses that further confirmed the linkage ofLy-6, Gpt-1, Gdc-4, andXp-14, the probable gene order beingGpt-11/Ly-6 Xp-14-Gdc-1.     

The physical map ofMus musculus chromosome 11 reveals evolutionary relationship with different syntenic groups of genes inHomo sapiens

Summary The physical localization of sequences homologous to three cloned genes was determined by in situ hybridization to metaphase chromosomes. Previous work had assigned the skeletal myosin heavy chain gene cluster (Myh), the functional locus for the cellular tumor antigen p53 (Trp53-1), and the cellular homologue of the viral erb-B oncogene (Erbb) toMus musculus chromosome 11 (MMU11). Our results provide regional assignments ofMyh andTrp53-1 to chromosome bands B2C, and ofErbb to bands A1A4. Taken together with in situ mapping of three other loci on MMU 11 (Hox-2 homeobox-containing gene cluster, theSparc protein, and theColla-1 collagen gene), which have been reported elsewhere, these data allowed us to construct a physical map of MMU11 and to compare it with the linkage map of this chromosome. The map positions of the homologous genes on human chromosomes suggest evolutionary relationships of distinct regions of MMU11 with six different human chromosome arms: 1p, 5q, 7p, 16p, 17p, and 17q. The delineation of conserved chromosome regions has important implications for the understanding of karyotype evolution in mammalian species and for the development of animal models of human genetic diseases.     

Linkage and cytogenetic maps of genes controlling endosperm storage proteins and isozymes in rye (Secale cereale L.)

Summary An F₁ plant fromSecale cereale ssp.ancestrale xtelocentric substitution lines3R of the cultivated rye Petkus spring was used as female in a cross with the inbred line Riodeva (I28), which has the standard chromosome arrangement. Single plants from this backcross progeny were analyzed for chromosome constitution, storage protein, and isozymic patterns. The seed protein loci were identified asSec-1a andSec-1b loci controlling 40-K-secalins and-secalins, respectively. These loci are located on the short arm of chromosome1R. TheSec-3 locus controlling high-molecular-weight secalins is located on the long arm of chromosome1R. A further seed protein locus,Pr-3 (55-K protein), was located on the short arm of chromosome1R. A linkage was found between the6Pgd-2 isozyme locus controlling 6-phosphogluconate dehydrogenase isozymes located on the long arm of chromosome1R and the four seed protein loci. The results favor the gene order:6Pgd-2 ...Sec-3 ... [centromere] ...Pr-3 ...Sec-1b ...Sec-1a. Other linkages detected werePer-3a andPer-3b (0.33±0.33 cM),Est-8 andEst-12 (0.33±0.33 cM), andGot-3 and centromere (20.57±2.42 cM). The proxidase (Per), glutamate oxaloacetate transaminase (Got), and esterase (Est) loci were located on chromosome arms2RS,3RL, and6RL, respectively. The distances and the maps obtained are compared with data available in the literature.     

DNA polymorphism in cytokine genes based on length variation in simple-sequence tandem repeats

The possibility of the involvement of cytokines in the genetic predisposition to various diseases has been suggested by a large variety of studies. However, the study of potential disease linkage of cytokine genes has been hampered by a lack of sufficiently polymorphic markers at the restriction fragment length polymorphism (RFLP) level. We have investigated the distribution, the length polymorphism, the informativeness, and the efficiency of analysis, of simple-sequence tandem repeats in the mouse cytokine genes. Highly polymorphic sequences have been identified in the IL-1, IL-1ra, IL-2, IL-4, IL-6, IL-7, and IFN- genes. The utility and the value of these sequences as gene markers is exemplified by mapping the IL-7 gene to mouse chromosome 3 close to pgk-1ps3 and Car-2 loci and the IFN- gene to chrrmosome 10 near the pg locus. Advantages of short tandemly repeated sequences as genetic markers are discussed in comparison with RFLPs.     

DNA polymorphisms and linkage relationship of the human complement componentC6,C7, andC9 genes

In this report we describe the linkage between genes encoding human complement componentsC6,C7, andC9. Polymorphisms have been described at the DNA level for theC7 andC9 genes. We have studied 20 individuals by Southern blot analysis with fourC6 cDNA subclones to detect restriction fragment length polymorphisms (RFLPs). We have found a Taq I polymorphism defined by two alleles of 8.0 (C6 H) and 6.0 (C6 L) kilobases (kb). RFLP segregation for theC6, C7, andC9 loci in informative families allowed us to estimate the maximum Lod scores at a recombination fraction of =0.0 (C6–C7), =0.0 (C7–C9), and =0.0 (C6–C9). Significant linkage disequilibrium was found betweenC6 andC7 and betweenC7 andC9 loci in directly determined haplotypes of unrelated parents. Data from this study show that the genes encoding the human terminal complement componentsC6, C7, andC9 define a cluster in the short arm of chromosome 5. We propose that the clusters involving theC8A andC8B and theC6, C7, andC9 genes be referred to as MACI and MACH, respectively.     

Inheritance and molecular mapping of two fertility-restoring loci for Honglian gametophytic cytoplasmic male sterility in rice (<Emphasis Type="Italic">Oryza sativa </Emphasis>L.)

The Honglian cytoplasmic male sterility (cms-HL) system, a novel type of gametophytic CMS in indica rice, is being used for the large-scale commercial production of hybrid rice in China. However, the genetic basis of fertility restoration (Rf) in cms-HL remains unknown. Previous studies have shown that fertility restoration is controlled by a single locus located on chromosome 10, close to the loci Rf1 and Rf4, which respond to cms-BT and cms-WA, respectively. To determine if the Rf locus for cms-HL is different from these Rf loci and to establish fine-scale genetic and physical maps for map-based cloning of the Rf gene, high-resolution mapping of the Rf gene was carried out using RAPD and microsatellite markers in three BCF₁ populations. The results of the genetic linkage analysis indicated that two Rf loci respond to cms-HL, and that these are located in different regions of chromosome 10. One of these loci, Rf5 , co-segregates with the SSR marker RM3150, and is flanked by RM1108 and RM5373, which are 0.9 cM and 1.3 cM away, respectively. Another Rf locus, designated as Rf6(t), co-segregates with RM5373, and is flanked by RM6737 and SBD07 at genetic distances of 0.4 cM. The results also demonstrated these loci are distinct from Rf1 and Rf4. A 105-kb BAC clone covering the Rf6(t) locus was obtained from a rice BAC library. The sequence of a 66-kb segment spanning the Rf6(t) locus was determined by a BLASTX search in the genomic sequence database established for the cultivar 93-11.Communicated by R. Hagemann     

Extragenic suppressor mutations of a β-tubulin mutation in the basidiomyceteCoprinus cinereus: Isolation and genetic and biochemical analyses

In total, 111 revertants were isolated from the oidia of a heat-sensitive, -tubulin mutant BEN193 (benA193) of the basidiomyceteCoprinus cinereus after mutagenesis by ultraviolet. Of the 111 revertants, 48 were genetically analyzed. In 15 of the 48 revertants, reversion was due to mutations at loci unlinked tobenA, whereas in the remaining 33 revertants, reversion was due to mutations withinbenA or at loci closely linked tobenA. The 15 extragenic suppressor mutations comprised three groups in terms of genetic linkage; two of them were designated asmipA andmipB. Suppressor mutations in the third group were found to bebenC, one of the four loci we have previously identified as genes conferring benomyl resistance. Biochemical analysis revealed thatbenC ⁺ is a structural gene for a major -tubulin in vegetative hyphae.     

Immune response deficiency of BSVS mice

The genetic control of the low response of BSVS mice to streptococcal Group A carbohydrate (GAC) was studied in crosses with responder A/J mice. F₁ mice were responders. In the backcross (BSVS × A/J)F₁ × BSVS mice, there were equal numbers of anti-GAC responder and nonresponder mice, indicating genetic control by a small number of major loci. The anti-GAC responses of the backcross mice showed no obligate linkage between responder status and A/JH-2 orIgC _H alleles. However, it was observed that the average anti-GAC titers were higher in backcross mice heterozygous at these loci. The above data, a lack of low-responder F₂ animals, and the segregation of a non-H-2-, non-IgC _H -linked locus in the first and second backcross mice, indicate that the defect in the BSVS anti-GAC responsiveness involves three loci: one linked toH-2, another linked toIgC _H , and a third locus —tentatively namedIr-GAC- not linked toH-2, IgC _H , orHbb.     

Fine mapping of three quantitative trait loci for late blight resistance in tomato using near isogenic lines (NILs) and sub-NILs

An earlier study identified quantitative trait loci (QTLs) lb4, lb5b, and lb11b for quantitative resistance to Phytophthora infestans (late blight) in a backcross population derived from crossing susceptible cultivated tomato (Lycopersicon esculentum) with resistant L. hirsutum. The QTLs were located in intervals spanning 28–47 cM. Subsequently, near-isogenic lines (NILs) were developed for lb4, lb5b, and lb11b by marker-assisted backcrossing to L. esculentum. Sub-NILs containing overlapping L. hirsutum segments across each QTL region were selected and used to validate the QTL effects, fine-map QTLs, and evaluate potential linkage drag between resistance QTLs and QTLs for horticultural traits. The NILs and sub-NILs were evaluated for disease resistance and eight horticultural traits at three field locations. Resistance QTLs were detected in all three sets of NIL lines, confirming the BC₁ mapping results. Lb4 mapped near TG609, and between TG182 and CT194, on chromosome 4, a 6.9-cM interval; lb5b mapped to an 8.8-cM interval between TG69a and TG413 on chromosome 5, with the most likely position near TG23; and lb11b mapped to a 15.1-cM interval on chromosome 11 between TG194 and TG400, with the peak centered between CT182 and TG147. Most QTLs for horticultural traits were identified in intervals adjacent to those containing the late blight resistance QTLs. Fine mapping of these QTLs permits the use of marker-assisted selection for the precise introgression of L. hirsutum segments containing late blight resistance alleles separately from those containing deleterious alleles at horticulturally important QTLs.Electronic Supplementary Material Supplementary material is available in the online version of this article at Communicated by D.B. Neale     

Identification of markers tightly linked to<Emphasis Type="Italic"> sbm</Emphasis> recessive genes for resistance to<Emphasis Type="Italic"> Pea seed-borne mosaic virus</Emphasis>

Two virus resistance loci on linkage groups II and VI have provided the only sources of natural resistance against Pea seed-borne mosaic virus (PSbMV, Potyviridae) in the important crop plant Pisum sativum L. A combination of parallel approaches was used to collate linked markers, particularly for sbm-1 resistance on linkage group VI. We have identified sequences derived from the genes for the eukaryotic translation initiation factors eIF4E and eIF(iso)4E as being very tightly linked to the resistance gene clusters on linkage groups VI and II, respectively. In particular, no recombinants between sbm-1 and eIF4E were found amongst 500 individuals of an F₂ cross between the BC₄ resistant line (JI1405) and its recurrent susceptible parent Scout. In a different mapping population, the gene eIF(iso)4E was also shown to be linked to sbm-2 on linkage group II. A parallel cDNA-AFLP comparison of pairs of resistant and susceptible lines also identified an expressed tag marker just 0.7 cM from sbm-1. eIF4E and eIF(iso)4E have been associated with resistance to related viruses in other hosts. This correlation strengthens the use of our markers as valuable tools to assist in breeding multiple virus resistances into peas, and identifies potential targets for resistance gene identification in pea.Communicated by C. Möllers     

Linkage arrangement of restriction fragment length polymorphism loci in Brassica oleracea

Summary A detailed genetic linkage map of Brassica oleracea was constructed based on the segregation of 258 restriction fragment length polymorphism loci in a broccoli × cabbage F₂ population. The genetic markers defined nine linkage groups, covering 820 recombination units. A majority of the informative genomic DNA probes hybridized to more than two restriction fragments in the F₂ population. Duplicate sequences having restriction fragment length polymorphism were generally found to be unlinked for any given probe. Many of these duplicated loci were clustered non-randomly on certain pairs of linkage groups, and conservation of the relative linkage arrangement of the loci between linkage groups was observed. While these data support previous cytological evidence for the existence of duplicated regions and the evolution of B. oleracea from a lower chromosome number progenitor, no evidence was provided for the current existence of blocks of homoeology spanning entire pairs of linkage groups. The arrangement of the analyzed duplicated loci suggests that a fairly high degree of genetic rearrangement has occurred in the evolution of B. oleracea. Several probes used in this study were useful in detecting rearrangements between the B. oleracea accessions used as parents, indicating that genetic rearrangements have occurred in the relatively recent evolution of this species.     

A new locus for autosomal dominant Charcot-Marie-Tooth disease type 2 (CMT2L) maps to chromosome 12q24

Charcot-Marie-Tooth disease (CMT) is one of the most common inherited neurological disorders with a prevalence estimated at 1/2500. The axonal form of this disorder is referred to as Charcot-Marie-Tooth type 2 disease (CMT2). Recently, a large Chinese family with CMT2 was found in the Hunan and Hubei provinces of China. The known loci for CMT1A, CMT2D, CMT1B (the same locus is also responsible for CMT2I and CMT2J), CMT2A, CMT2E, and CMT2F were excluded in this family by linkage analysis. A genome-wide screening was then carried out, and the results revealed linkage of CMT2 to a locus at chromosome 12q24. Haplotype construction and analyses localized this novel locus to a 6.8-cM interval between microsatellite markers D12S366 and D12S1611. The maximal two-point LOD score of 6.35 and multipoint LOD score of 8.08 for marker D12S76 at a recombination fraction () of 0 strongly supported linkage to this locus. Thus, CMT2 neuropathy in this family represents a novel genetic entity that we have designated as CMT2L.     

Tagging and combining bacterial blight resistance genes in rice using RAPD and RFLP markers

Four genes of rice,Oryza sativa L., conditioning resistance to the bacterial blight pathogenXanthomonas oryzae pv.oryzae (X. o. pv.oryzae), were tagged by restriction fragment length polymorphism (RFLP) and random amplified polymorphic DNA (RAPD) markers. No recombinants were observed betweenxa-5 and RFLP marker lociRZ390, RG556 orRG207 on chromosome 5.Xa-3 andXa-4 were linked to RFLP locusXNpb181 at the top of chromosome 11, at distances of 2.3 cM and 1.7 cM, respectively. The nearest marker toXa-10, also located on chromosome 11, was the RAPD locusO07 ₂₀₀₀ at a distance of 5.3 cM. From this study, the conventional map [19, 28] and two RFLP linkage maps of chromosome 11 [14, 26] were partially integrated. Using the RFLP and RAPD markers linked to the resistance genes, we selected rice lines homozygous for pairs of resistance genes,Xa-4 +xa-5 andXa-4 +Xa-10. Lines carryingXa-4 +xa-5 andXa-4 +Xa-10 were evaluated for reaction to eight strains of the bacterial blight pathogen, representing eight pathotypes and three genetic lineages. As expected, the lines carrying pairs of genes were resistant to more of the isolates than their single-gene parental lines. Lines carryingXa-4 +xa-5 were more resistant to isolates of race 4 than were either of the parental lines (quantitative complementation). No such effects were seen forXa-4 +Xa-10. Thus, combinations of resistance genes provide broader spectra of resistance through both ordinary gene action expected and quantitative complementation.     

Interaction ofH-2 and nonH-2 linked genes in the regulation of antibody response to a threshold dose of sheep erythrocytes

The antibody response to a threshold dose (¹⁰) of SE was studied in the High responder line (H) and the Low responder line (L) of mice obtained by bidirectional selective breeding for the character quantitative agglutinin response to an optimal dose of SE, and in interline hybrids: F₁, F₁ and both backcrosses. Whereas the interline difference in agglutinin responses at the optimal dose is due to the additive effect of about ten independently segregating loci, one of which isH-2 linked, the responsiveness to the threshold dose is determined by the effect of two loci. The direction of the dominance effect also varies with the antigen dose: high responsiveness is partially dominant at the optimal dose while at the threshold dose nonresponder character is partially dominant. The role of theH-2 linked locus was investigated. It has been demonstrated that on an identical background (equivalent to that of F₁ hybrids) this locus is responsible for 12% of the interline difference at the optimal antigen dose, and for 61% at the threshold antigen dose. For the two antigen doses, the quantitative effect of theH-2 locus is in agreement with the estimate of the number of loci obtained by variance analysis. The intervention of a second gene, non-H-2 linked, in the regulation of responsiveness to 10⁶ SE is demonstrated by appropriate assortative matings. The interaction between the two genes is discussed.     

A linkage map ofBrassica rapa (syn.campestris) based on restriction fragment length polymorphism loci

Summary A detailed linkage map ofB. rapa (syn.campestris) was constructed based on segregation of 280 restriction fragment length polymorphism loci, detected by using 188 genomic DNA clones as probes on DNAs from a F₂ population of Chinese cabbage MichihilF×Spring broccoli. These genetic markers covered 1,850 centiMorgans (cM) and defined ten linkage groups, which equals the haploid chromosome number of this species. Extensive sequence duplication was evident by the detection of two or more segregating loci with each of 69 clones (36.7% of the total). Although some duplicated loci were randomly distributed throughout the genome, many had linkage arrangements that were conserved on different linkage groups, suggesting that large chromosome fragments were present in multiple copies. However, conservation in the linkage arrangement of duplicate loci throughout entire pairs of linkage groups was not observed. Single-copy loci were often found to be located within conserved duplicated regions, and linkage distances between some loci having conserved duplicated arrangements were substantially different between the duplicated regions. Structural rearrangements, such as insertions, deletions, and inversions or combinations of these events, seemed to be related to the alternations of map distances between duplicated loci and to the dispersal of duplicated chromosome fragments. These results suggest thatB. rapa has evolved in part by duplication of chromosomes or large chromosome fragments with subsequent structural rearrangements.     

YAC Contigs of theRab1andwobbler(wr) Spinal Muscular Atrophy Gene Region on Proximal Mouse Chromosome 11 and of the Homologous Region on Human Chromosome 2p

Despite rapid progress in the physical characterization of murine and human genomes, little molecular information is available on certain regions, e.g., proximal mouse chromosome 11 (Chr 11) and human chromosome 2p (Chr 2p). We have localized thewobblerspinal atrophy genewrto proximal mouse Chr 11, tightly linked toRab1,a gene coding for a small GTP-binding protein, andGlns-ps1,an intronless pseudogene of the glutamine synthetase gene. We have now used these markers to construct a 1.3-Mb yeast artificial chromosome (YAC) contig of theRab1region on mouse Chr 11. Four YAC clones isolated from two independent YAC libraries were characterized by rare-cutting analysis, fluorescencein situhybridization (FISH), and sequence-tagged site (STS) isolation and mapping.Rab1andGlns-ps1were found to be only 200 kb apart. A potential CpG island near a methylatedNarI site and a trapped exon,ETG1.1,were found between these loci, and a new STS,AHY1.1,was found over 250 kb fromRab1.Two overlapping YACs were identified that contained a 150-kb region of human Chr 2p, comprising theRAB1locus,AHY1.1,and the human homologue ofETG1.1,indicating a high degree of conservation of this region in the two species. We mappedAHY1.1and thus humanRAB1on Chr 2p13.4–p14 using somatic cell hybrids and a radiation hybrid panel, thus extending a known region of conserved synteny between mouse Chr 11 and human Chr 2p. Recently, the geneLMGMD2Bfor a human recessive neuromuscular disease, limb girdle muscular dystrophy type 2B, has been mapped to 2p13–p16. The conservation between the mouseRab1and humanRAB1regions will be helpful in identifying candidate genes for thewobblerspinal muscular atrophy and in clarifying a possible relationship betweenwrandLMGMD2B.     

Evidence for a genetic duplication involving alcohol dehydrogenase genes inCeratitis capitata

AnAdh duplication is described in the medflyCeratitis capitata. Evidence is presented for two separateAdh ₁ andAdh ₂ structural loci mapping at a distance of 0.49 recombination unit from each other. By deletion mapping theAdh region has been cytologically located near the free end of the left arm of the second chromosome within an area between 2C;3A segments of the polytene chromosome. The genetic analysis of the region aroundAdh has identified seven neighboring genes (Acon ₁,Mpi, Est ₆,Aox, Xdh, Mdh ₂,Lsp _I) which identify the linkage group D. The orientation of loci with regard to the centromere sets the origin of the map of the left arm of the second chromosome close to the twoAdh loci.Research supported by National Research Council of Italy, Special Project RAISA, Subproject N.2, Paper N.200. Grants from I.A.E.A. (International Atomic Energy Agency, Vienna, Austria) and from European Communities Commission, Second R&D Programme Science and Technology for Development also contributed to this work.     

Inheritance of allozyme loci inBombina: One linkage group established

Two hybridizing European species of fire-bellied toads,Bombina bombina andB. variegata, have alternate electromorphs fixed at a number of allozyme loci. Segregation of alleles at seven allozyme loci (Ldh-1, Mdh-1, Ak, Ck, Gpi, Np, andEst-) was studied in a backross progeny of an F₁ interspecific hybrid male and aB. bombina female. Mendelian inheritance of allozyme forms at all seven loci was ascertained. Except for two loci,Gpi andEst-, which were found to be tightly linked (1 cM apart), other loci showed independent segregation.     

Esterase-29 (ES-29): Biochemical characterization and control by two independent gene loci of a testosterone-dependent mouse serum esterase

Biochemistry and genetics of a testosterone-dependent murine serum esterase designated esterase-29 (ES-29) are described. The enzyme was identified after disc electrophoresis and subsequent staining for esterase using -naphthyl acetate as the substrate. It was inhibited by bis-p-nitrophenyl phosphate and was resistant top-chlorophenylsulphonate and hence was classified as carboxylesterase EC 3.1.1.1. The molecular mass was estimated to be about 130 kDa. It was shown that ES-29 is under the control of two independent genes. The first, termed Es-29, is suggested to be a structural locus, linked to the cluster-2 esterase loci on chromosome 8. Three alleles atEs-29, Es-29 ^a, Es-29^b, andEs-29 ^care distinguished, which determine absence (SEG/1), strong activity (BALB/cJ), and low activity (MOLH/Fre), respectively. The second locus, termedMse-1 (serum esterase modifying factor), was found to be closely linked toPre-2 on chromosome 12 and is suggested to be a modifying or regulatory gene. Two alleles were distinguished,Mse-1 ^a(BALB/cJ) andMse-1 ^m(MOL3/JA, CasBgr), which determine whether ES-29 appears as a single band or a double band, respectively.Mse-1 ^mis dominant toMse-1 ^a.This work was supported by the Deutsche Forschungsgemeinschaft. This is communication No. 70 of a research program devoted to the cellular distribution, genetics, and regulation of nonspecific esterases.