Chromosomal Location Of Gene Research Articles

LOW OCCURRENCE OF GENE TRANSPOSITION EVENTS DURING THE EVOLUTION OF THE GENUS DROSOPHILA

The role played by gene transpositions during the evolution of eukaryotic genomes is still poorly understood and indeed has been analyzed in detail only in nematodes. In Drosophila, a limited number of transpositions have been detected by comparing the chromosomal location of genes between different species. The relative importance of gene transposition versus other types of chromosomal rearrangements, for example, inversions, has not yet been evaluated. Here, we use physical mapping to perform an extensive search for long-distance gene transpositions and assess their impact during the evolution of the Drosophila genome. We compare the relative order of 297 molecular markers that cover 60% of the euchromatic fraction of the genome between two related Drosophila species and conclude that the frequency of gene transpositions is very low, namely one order of magnitude lower than that of nematodes. In addition, gene transpositions seem to be events almost exclusively associated with genes of repetitive nature such as the Histone gene complex (HIS-C).

Detection of modifier loci influencing the lung phenotype of cystic fibrosis knockout mice.

The variable severity of lung disease associated with cystic fibrosis (CF) cannot be explained by the genotype of the cystic fibrosis transmembrane conductance regulator (CFTR) locus alone. Lung disease has been reported in a congenic CF mouse model of C57BL/6J genetic background (B6 CF), in the absence of detectable infection, but not in CF mice of mixed genetic background, nor in wild-type animals maintained in identical environments. In this report, studies are presented to show that the same CF mutation in mice of a BALB/c background (BALB CF) results in minimal lung disease. By 12 weeks of age B6 CF mice developed a lung disease consisting of mononuclear cell interstitial infiltrate and fibrosis, and BALB CF or littermate control mice developed minimal histopathology. Therefore, it is possible to identify the chromosomal locations of genes that can contribute to the susceptibility to lung disease in B6 CF mice compared with BALB CF mice by means of a quantitative trait loci (QTL) mapping strategy based on the variable histology of the (B6 x BALB) F2 CF mice. Significant linkage of the fibrotic lung phenotype was detected for a region on Chromosome (Chr) 6, defined by markers D6Mit194 to D6Mit201, and suggestive linkage was found for regions on Chr 1, 2, 10, and 17. Additional loci, suggestive of linkage, were also detected for the interstitial thickening phenotype. Most of these putative loci are specific to the sex of the animals. These results suggest that multiple genes can influence the severity of CF lung disease in mice.

Mapping of genetic factors influencing the weight of cystic fibrosis knockout mice.

One of the poorly understood clinical manifestations of cystic fibrosis (CF) is low body weight. Mice in which the CF causative gene, cystic fibrosis transmembrane conductance regulator (Cftr), has been knocked out reflect this as they are smaller than age-matched littermates. The variable weight of F2 Cftr -/- (CF) mice derived from a cross between congenic C57BL/6J and BALB/cJ Cftr heterozygotic mice permits the mapping of modifiers of this cystic fibrosis phenotype. In this report, quantitative trait loci (QTL) mapping was used to identify the chromosomal locations of genes that contribute to the body weight of 12-week-old F2 CF mice. Five loci of CF body weight were detected with four of the five acting in a sex-specific manner. Significant linkage of the phenotype to a region of Chromosome (Chr) 13 from D13Mit179 to D13Mit254 (LOD = 4.2) was established in female mice; and suggestive loci on Chrs 7 and 10 were identified. The weights of F2 male CF mice were suggestively linked to regions of Chrs 1 and 6, and to the same locus on Chr 7 as in female mice. The suggestive loci did not influence the weight of the limited set of control mice and thus are presumed to be CF specific in their effects. Further study of these putative CF body weight modifiers may provide insight on the pathogenesis of cystic fibrosis.

Radiation hybrid mapping of five muscarinic acetylcholine receptor subtype genes in Rattus norvegicus

Acetylcholine is the main neurotransmitter of the vestibular efferent system and a wide variety of muscarinic and nicotinic acetylcholine receptors are expressed in the vestibular periphery. The role of these receptors and in particular the role of muscarinic acetylcholine receptors in the physiology of the vestibular neuroepithelium is not understood. Congenic and consomic rats are a convenient way to investigate the involvement of candidate genes in the manifestation of defined traits. To use congenic or consomic rats to elucidate the roles of these receptors in vestibular physiology or pathology the chromosomal location of the genes encoding these receptors has to be determined. Using radiation hybrid (RH) mapping and a rat RH map server ( www.rgd.mcw.edu/RHMAP SERVER/), we determined the chromosomal locations of the muscarinic acetylcholine receptor genes in the rat ( Rattus norvegicus). The m1–m5 muscarinic subtypes mapped to the following chromosomes: Chrm1, chromosome 1; Chrm2, chromosome 4; Chrm3, chromosome 17; Chrm4, chromosome 3; and Chrm5, chromosome 3. With the chromosomal location for each of these muscarinic subtypes known, it is now possible to develop congenic and consomic strains of rats that can be used to study the functions of each of these subtypes.

Chromosomal location of genes for resistance to powdery mildew in Chinese wheat lines Jieyan 94-1-1 and Siyan 94-1-2

Two Chinese wheat lines Jieyan 94-1-1 and Siyan 94-1-2 are resistant to all 120 isolates of Blumeria graminis f. sp. tritici maintained in Weihenstephan, Germany. Monosomic analyses employing the susceptible set of 21 Chinese Spring monosomic lines revealed that the line Jieyan 94-1-1 carries one dominant gene on translocated wheat/rye chromosome 1B/1R and one recessive gene on chromosome 7B, whereas line Siyan 94-1-2 possesses one recessive gene on chromosome 7B and one dominant gene on chromosome 5D. Allelism tests in combination with the use of specific isolates comfirmed that the dominant genes in Jieyan 94-1-1 and Siyan 94-1-2 are Pm8 and Pm2, respectively. The recessive genes present in each of the two lines are shown to be new alleles located on chromosome 7B at the pm 5 locus. The two genes are tentatively designated mljy in Jieyan 94-1-1 and mlsy in Siyan 94-1-2, respectively.

Chromosomal location of genes for resistance to powdery mildew in Chinese wheat lines Jieyan 94-1-1 and Siyan 94-1-2

Chromosomal location of genes for resistance to powdery mildew in Chinese wheat lines Jieyan 94-1-1 and Siyan 94-1-2

Chromosomal location of a Triticum dicoccoides-derived powdery mildew resistance gene in common wheat by using microsatellite markers.

The powdery mildew resistance has been transferred from an Israeli wild emmer (Triticum dicoccoides) accession "G-305-M" into common wheat by crossing and backcrossing (G-305-M/781//Jing 411*3). Genetic analysis showed that the resistance was controlled by a single dominant gene at the seedling stage. Among the 102 pairs of SSR primers tested, four polymorphic microsatellite markers (Xpsp3029, Xpsp3071, Xpsp3152 and Xgwm570) from the long arm of chromosome 6A were mapped in a BC(2)F(3) population segregating for powdery mildew resistance and consisting of 167 plants. The genetic distances between the resistance gene and these four markers were: 0.6 cM to Xpsp3029, 3.1 cM to Xpsp3071, 11.2 cM to Xpsp3152 and 20.4 cM to Xgwm570, respectively. The order of these microsatellite loci agreed well with the established microsatellite map of chromosome arm 6AL. We concluded that the resistance gene was located on the long arm of chromosome 6AL. Based on the origin and chromosomal location of the gene, it is suggested that the resistance gene derived from "G-305-M" is a novel powdery mildew resistance gene and is temporarily designated MlG.

Chromosomal effects in the endogenous contents of non‐structural carbohydrates and proteins measured in wheat substitution lines

AbstractIn hexaploid bread wheat, Triticum aestivum (2n = 6x = 42), little work has been carried out to study the genetic control of the synthesis of reduced, non‐reduced and total non‐structural carbohydrates and soluble proteins in aerial and rooting structures. The aim of this paper was to determine the chromosomal location of genes determining carbohydrate and protein synthesis that could be used for diagnostic selection in segregating breeding populations. A set of wheat intervarietal chromosome substitution lines [‘Chinese Spring’ (CS) × synthetic wheat (Triticum diccocoides×Aegilops squarrosa) (Syn)], was used. Plants were cultivated in hydroponic solutions to the fully expanded third leaf stage. Carbohydrate and protein contents and dry matter were determined for aerial and root parts. The root dry weight did not show significant differences between the parental varieties and the substitution lines, except for 5A, 2B and 6B, which had significantly lower dry weights. The aerial dry weight was significantly higher for Syn and the 2A substitution line. The ratio aerial dry weight/root dry weight was significantly higher in Syn, 1A, 2A and 4B. The protein content of the plant showed highly significant differences between both parental lines but 6A and 1D of the substitution lines showed highly significant differences, with contents as high as that for Syn. Syn produced significantly lower total aerial carbohydrates. The substitution lines 2A, 5A, 6A, 7A, 2B, 3D, 5D and 6D showed highly significant total carbohydrate content increases in the aerial parts compared with both parental lines. The non‐reduced carbohydrate contents showed a pattern similar to that of the total carbohydrates. Syn had a lower reduced carbohydrate content than CS. Only the 5A, 2B, and 1D substitution lines had a highly significantly different content of reduced carbohydrates than CS. In roots, Syn produced the lowest values for every type of sugar. The highest significant values for total carbohydrates were found in substitution lines 2B, 4B, 5B, 6B, 1D and 6D. The non‐reduced carbohydrate levels were significantly higher than CS in 2B, 5B, 6B and 6D substitution lines. Only the substitution lines 3B and 1D showed a significantly higher reduced carbohydrate content in roots compared with CS. The photoassimilate partitioning in Syn, 1 A, 2A and 4B favoured the aerial parts but, in contrast, higher partitioning to the roots was found in the 7B, 1D and 3D substitution lines. Both groups appear to carry interesting patterns worth incorporating in wheat cultivars.

Mapping of the QTL (quantitative trait locus) conferring partial resistance to leaf blast in rice cultivar Chubu 32.

The rice cultivar Chubu 32 possesses a high level of partial resistance to leaf blast. The number and chromosomal location of genes conferring this resistance were detected by restriction fragment length polymorphism (RFLP) linkage mapping and quantitative trait locus (QTL) analysis. For the mapping, 149 F(3) lines derived from the cross between rice cultivar Norin 29, with a low level of partial resistance, and Chubu 32 were used, and their partial resistance to leaf blast was assessed in upland nurseries. A linkage map covering six chromosomes and consisting of 36 RFLP markers was constructed. In the map, only one significant QTL (LOD>2.0) for partial resistance was detected on chromosome 11. This QTL explained 45.6% of the phenotypic variation. The segregation ratio of the F3 lines was 3:1 for partial resistance to susceptibility. These results suggest that the partial resistance in Chubu 32 is controlled by a major gene.

Chromosomal location of genes for resistance to powdery mildew in common wheat (Triticum aestivum L. em Thell.) 7. Gene Pm29 in line Pova

Chromosomal localization and linkage mapping of a powdery mildewresistance gene were conducted in the resistant wheat line Pova, derivedfrom a Triticum aestivum cv. Poros-Aegilops ovata-alien additionline. Monosomic analysis revealed that a major dominant gene was locatedon chromosome 7D. This gene possessed a distinct disease response patternagainst a differential set of Blumeria graminis tritici isolates andsegregated independently from resistance gene Pm19 also located onwheat chromosome 7D. Molecular genetic analysis showed that theresistance gene in Pova was specifically located on the long arm ofchromosome 7D closely linked to one RFLP and three AFLP markers. It isproposed that the new gene be designated Pm29.

Chromosome location of genes controlling the content of dietary fibre and arabinoxylans in rye

To identify the chromosomes responsible for synthesis of dietary fibre (DF)and arabinoxylans (AX) in rye, four sets of disomic and several ditelosomicrye addition lines of wheat, several centric wheat-rye translocation lines ofwheat and two sets of single D(R) substitution lines of hexaploid triticalewere tested and compared to the parental lines. The DF and AX levels wereanalysed as soluble and insoluble fractions. All octoploid triticales and alladdition lines had higher contents of the insoluble DF and AX fractionsthan wheats and these were strongly correlated with test weight. Becausedifferent additions of rye chromosomes to wheat have different effects onkernel characteristics, only the results of the soluble fractions appearsignificant. Among rye additions to Chinese Spring (CS), a wheat with lowcontent of both soluble fractions, rye chromosomes 2R, 5R and 6R wereassociated with significantly increased amounts of soluble DF and AX.Among rye additions to BH1146 wheat that had substantially highercontent of soluble fibre and arabinoxylans than CS, addition 5R resultedin significantly higher amounts while additions 1R, 3R, 4R and 7R insignificantly lower levels of soluble DF and AX. These results were partiallyconfirmed in substituted triticales, as removal of chromosomes 5R and 6Rresulted in reductions of soluble DF and AX relative to the originalcultivars. Analyses of ditelosomic rye additions to wheat and of centricwheat-rye translocation lines of wheat indicated that the factors responsiblefor increased soluble DF and AX contents in 2R were located on botharms, and in 6R either on S or in the proximal part of L. However,chromosome arms 3RL and 7RL also were associated with higher solubleDF and AX even though complete chromosomes did not show any effect.This suggests that factors with contrasting effects could be located on theopposite arms of the same chromosome. Clearly, the DF and AX contentsin rye are controlled by many factors scattered throughout the genome andtherefore, may not be easily manipulated in breeding.

Genetics of intake of umami-tasting solutions by mice

Inbred strains of mice provide a powerful tool for genetic dissection of quantitative behavioral traits. We have investigated intake of the umami-tasting substances monosodium glutamate (MSG) and inosine 5'-monophosphate (IMP) in inbred mice. Studies with two inbred strains, C57BL/6ByJ and I29P3/J have revealed strain differences in voluntary consumption of 300 mM MSG which depend, at least partially, on postingestive effects of solution consumption, as well as on strain differences in preferences for much lower MSG concentrations, which depend on perception. The strain difference in MSG acceptance was in the opposite direction to the strain difference in NaCl acceptance and was unrelated to sweetener preference in the F(2) generation. Thus, the strain differences in MSG acceptance are not related to the strain differences in salty or sweet taste responsiveness and most likely represent specific umami taste responsiveness. High acceptance of MSG solutions by the C57BL/6ByJ mice was inherited us a recessive trait in the F(2) hybrid generation. Further genetic linkage analyses using the F(2) hybrids are being conducted to map chromosomal locations of genes determining the strain difference in MSG acceptance. At the same time, a wider range of inbred strains is being phenotyped in a search for new model systems for studying umami substance acceptance.

Identification of a polymorphic mucin-like gene expressed in the midgut of the mosquito, Aedes aegypti, using an integrated bulked segregant and differential display analysis.

The identification of putative differentially expressed genes within genome regions containing QTL determining susceptibility of the mosquito, Aedes aegypti, to the malarial parasite, Plasmodium gallinaceum, was investigated using an integrated, targeted approach based on bulked segregant and differential display analysis. A mosquito F2 population was obtained from pairwise matings between the parasite-susceptible RED strain and the resistant MOYO-R substrain. DNA from female carcasses was used to genotype individuals at RFLP markers of known chromosomal position around the major QTL (pgs 1). Midguts, dissected 48 hr after an infected blood meal, were used to prepare two RNA bulks, each representing one of the parental genotypes at the QTL interval. The RNA bulks were compared by differential display PCR. A mucin-like protein gene (AeIMUC1) was isolated and characterized. The gene maps within the pgs 1 QTL interval and is expressed in the adult female midgut. AeIMUC1 RNA abundance decreased with time after blood meal ingestion. No differential expression was observed between the two mosquito strains but three different alleles with inter- and intrastrain allelic polymorphisms including indels and SNPs were characterized. The AeIMUC1 gene chromosome location and allelic polymorphisms raise the possibility that the protein might be involved in parasite-mosquito interactions.

Chromosomal Control of Albumins and Globulins in Wheat Grain Assessed using Different Fractionation Procedures

A systematic study of the water-soluble (albumin) and salt-soluble (globulin) proteins of wheat flour, by analysis of null genetic lines using different methods of protein separation, has established the location of several of their genes on individual chromosomes. SDS-PAGE analysis of water-soluble proteins indicated the chromosomal location of polypeptides ofMr 64 000, Mr62 000 and Mr16 000 on 4DL, 4BS and 3DS respectively. Similarly, two globulin polypeptides of Mr38 000 and Mr39 000 were assigned to chromosomes 2A, 2B, 2D, 3BS, 3DS, 4DS, 5DL, 6DS, 7BS or 7DL using isoelectric focusing. In addition, several non-gluten proteins have been mapped on chromosome 1D, 3AL, 3BS, 3DS, 4AL, 4BS, 4DS, and 5DL by reversed-phase HPLC (RP-HPLC). The proteins separated by RP-HPLC were also correlated with proteins resolved with other methods. The polypeptides assigned to different chromosomes using SDS-PAGE and isoelectric focusing were also analysed by 2-D electrophoresis to confirm the chromosomal location of genes controlling expression of particular polypeptides. Some other proteins that were not resolved by either method alone, were able to be mapped on chromosomes using 2-D electrophoresis. The chromosome-specific proteins are now being used to develop chromosome-specific markers, which may be valuable to discover spontaneous deletions as well as natural translocations from alien species.

Chromosomal location of genes for resistance to powdery mildew in common wheat (Triticum aestivum L. em Thell.) 6. Alleles at the Pm5 locus

Genetic characterization of powdery mildew resistance genes were conducted in common wheat cultivars Hope and Selpek possessing resistance gene Pm5, cvs. Ibis and Kormoran expressing resistance gene Mli, a backcross-derived line IGV 1–455 and a Triticum sphaerococcum var. rotundatum Perc. line Kolandi. Monosomic analyses revealed that one major recessive gene is located on chromosome 7B in the lines IGV 1–455 and Kolandi. Allelism tests of the F2 and F3 populations involving the tested resistant lines crossed with either cv. Hope or Selpek indicated that their resistance genes are alleles at the Pm5 locus. The alleles are now designated Pm5a in Hope and Selpek, Pm5b in Ibis and Kormoran, Pm5c in T. sphaerococcum var. rotundatum line Kolandi, and Pm5d in backcross-derived line IGV 1–455, respectively.

Chromosomal location of genes conferring the tolerance to Pi starvation stress and acid phosphatase (APase) secretion in the genome of rye (Secale L.)

Rye and wheat can easily be crossed, providing the possibility to create disomic addition lines, which contain a pair of homologous chromosomes of rye in the genetic background of wheat. We obtained and used a set of Chinese Spring-Imperial (CS-IMP) disomic addition lines for facilitating the location of genes responsible for P starvation tolerance and root secretion of APase on the specific chromosome(s) of rye. A soil culture experiment showed that different chromosomes of Imperial rye in the background of common wheat Chinese Spring (CS) contributed differently to the trait investigated. Chromosome 1R and 7R of rye might carry genes responsible for tolerance to Pi starvation stress, while 5R might carry unfavorable genes regarding Pi starvation tolerance. APase activities of different disomic addition lines as well as background parent CS were 1∼12 and 2∼6 folds higher under Pi starvation conditions than under Pi sufficient conditions in terms of APase secretion on individual plant root system basis (µg/plant per h) and on unit dry root weight basis (µg/g per h) respectively. Among 7 disomic addition lines, DA1R secreted more APase than the rest of lines in both parameters mentioned above under Pi starvation condition. IEF (Iso-electric Focussing) diagram of APase isozymes clearly showed that chromosome 1R carries Pi starvation-inducible APase genes. Our results showed that genes conferring Pi starvation tolerance might be carried on 1R and 7R in the genome of rye, and the Pi starvation-inducible APase gene(s) carried in 1R might be one of the reasons of the better performance of line 1R under Pi starvation condition. Abbreviations: CS-IMP DA line – Chinese Spring-Imperial disomic addition line; APase – Acid phosphatase; MVGY – Mean Value of Individual Grain yield; RGY – Relative Grain Yield; IEF – Iso-electric Focussing; NPP – p-Nitrophenyl Phosphate; NP – p-Nitrophenol; Pi – inorganic orthophosphate

Inheritance of Gliadin and Glutenin Proteins in Four Durum Wheat Crosses

The F2 progenies, from four crosses between landraces and commercial Portuguese durum wheat cultivars, were analysed by electrophoresis for storage protein composition and genetic segregation. The chromosomal location of genes was determined for gliadin and glutenin allelic variations at the Gli-A1, Glu-A3 and Glu-A1 on 1A; Gli-B1, Glu-B3, Gli-B3, Glu-B2 and Glu-B1 on 1B; Gli-A2 on 6A and Gli-B2 on 6B. The protein patterns of landraces were uncommon and four new alleles were identified at different loci in chromosome 1 and four in the chromosome 6B (Gli-B2). The presence of γ-gliadin bands encoded at the Gli-B2 locus was also found.

Chromosomal location of genes for purple grain colour introgressed in common wheat

Monosomic lines representing the A and B genomes of ‘Chinese Spring’ were used as female parental forms for the chromosomal localisation of genes controlling purple grain colour. The male parent was a near-isogenic purple derivative of ‘Saratovskaya 29’. The complementary genes Pp2 and Pp1 were located on chromosomes 6A and 7B, respectively.

Inheritance of ventilatory behavior in rodent models

Studies in mice and rats support the hypothesis that ventilation and its components (frequency and tidal volume) are determined to a significant extent by genetic mechanisms. The question can no longer be ‘is there a genetic effect?’ but rather ‘how strong is the genetic component?’ and ‘what genes are involved?’ The computational analyses of selectively bred animals now offer powerful tools to begin to dissect the genetic factors that track with ventilatory traits. Control of the conditions in the colony and in the laboratory are keys to reducing the environmental ‘noise’ and increasing the likelihood of detecting gene loci that correlate quantitatively with phenotype values before and during the response to chemosensory challenges. Knowing the chromosomal location of genes for ventilation will then permit the identification of proteins systems responsible for the structural and functional components for respiration.

Intake of Umami-Tasting Solutions by Mice: A Genetic Analysis

In two-bottle preference tests with water and solutions of monosodium glutamate (MSG) and inosine-5'-monophosphate (IMP), mice from the C57BL/6ByJ inbred strain consumed more and had higher preferences for these solutions compared with mice from the 129/J strain. The C57BL/6ByJ mice consumed 300 mmol/L MSG in large amounts, which were comparable to intakes of highly preferred solutions of sweeteners. The strain differences in voluntary consumption of 300 mmol/L MSG depended at least in part on postingestive effects because prior experience with MSG influenced the expression of the strain difference in MSG acceptance. The strain difference in MSG acceptance was in the opposite direction to the strain difference in NaCl acceptance and was not affected by previous consumption of saccharin. Although the C57BL/6ByJ mice had higher avidity for both MSG and sweeteners than did the 129/J mice, there was no correlation between preferences for these solutions in the second hybrid generation (F(2)) derived from these two strains. Thus, the strain differences in MSG acceptance are not related to the strain differences in salty or sweet taste responsiveness and most likely represent specific umami taste responsiveness. High acceptance of MSG solutions by the C57BL/6ByJ mice was inherited as a recessive trait in the F(2) generation. Further genetic linkage analyses using the F(2) hybrids are being conducted to map chromosomal locations of genes determining the strain difference in MSG acceptance.