Mouse to human comparative genetics reveals a novel immunoglobulin E-controlling locus on Hsa8q12

Atopy is a predisposition to hyperproduction of immunoglobulin E (IgE) against common environmental allergens. It is often associated with development of allergic diseases such as asthma, rhinitis, and dermatitis. Production of IgE is influenced by genetic and environmental factors. In spite of progress in the study of heredity of atopy, the genetic mechanisms of IgE regulation have not yet been completely elucidated. The analysis of complex traits can benefit considerably from integration of human and mouse genetics. Previously, we mapped a mouse IgE-controlling locus Lmr9 on chromosome 4 to a segment of <9 Mb. In this study, we tested levels of total IgE and 25 specific IgEs against inhalant and food allergens in 67 Czech atopic families. In the position homologous to Lmr9 on chromosome 8q12 marked by D8S285, we demonstrated a novel human IgE-controlling locus exhibiting suggestive linkage to composite inhalant allergic sensitization (limit of detection, LOD = 2.11, P = 0.0009) and to nine specific IgEs, with maximum LOD (LOD = 2.42, P = 0.0004) to plantain. We also tested 16 markers at previously reported chromosomal regions of atopy. Linkage to plant allergens exceeding the LOD > 2.0 was detected at 5q33 (D5S1507, LOD = 2.11, P = 0.0009) and 13q14 (D13S165, LOD = 2.74, P = 0.0002). The significant association with plant allergens (quantitative and discrete traits) was found at 7p14 (D7S2250, corrected P = 0.026) and 12q13 (D12S1298, corrected P = 0.043). Thus, the finding of linkage on chromosome 8q12 shows precision and predictive power of mouse models in the investigation of complex traits in humans. Our results also confirm the role of loci at 5q33, 7p14, 12q14, and 13q13 in control of IgE. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Systems genetic analysis of binge-like eating in a C57BL/6J x DBA/2J-F2 cross

Binge eating is a heritable trait associated with eating disorders and refers to the rapid consumption of a large quantity of energy-dense food that is, associated with loss of control and negative affect. Binge eating disorder is the most common eating disorder in the United States; however, the genetic basis is unknown. We previously identified robust mouse inbred strain differences between C57BL/6J and DBA/2J in binge-like eating of sweetened palatable food in an intermittent access, conditioned place preference paradigm. To map the genetic basis of changes in body weight and binge-like eating (BLE) and to identify candidate genes, we conducted quantitative trait locus (QTL) analysis in 128 C57BL/6J x DBA/2J-F2 mice combined with PheQTL and trait covariance analysis in GeneNetwork2 using legacy BXD-RI trait datasets. We identified a QTL on Chromosome 18 influencing changes in body weight across days in females (log of the odds [LOD] = 6.3; 1.5-LOD: 3–12 cM) that contains the candidate gene Zeb1. We also identified a sex-combined QTL influencing initial palatable food intake on Chromosome 5 (LOD = 5.8; 1.5-LOD: 21–28 cM) that contains the candidate gene Lcorl and a second QTL influencing escalated palatable food intake on Chromosome 6 in males (LOD = 5.4; 1.5-LOD: 50–59 cM) that contains the candidate genes Adipor2 and Plxnd1. Finally, we identified a suggestive QTL in females for slope of BLE on distal Chromosome 18 (LOD = 4.1; p = 0.055; 1.5-LOD: 23–35 cM). Future studies will use BXD-RI strains to fine map loci and support candidate gene nomination for gene editing.     

Chromosome numbers are not fixed in Agaonidae (Hymenoptera: Chalcidoidea)

Agaonidae (the pollinators of fig trees, Ficus spp., Moraceae) are a distinctive family of chalcid wasps with uncertain affinities within the Chalcidoidea. Chromosome numbers have only been described previously for one species (Blastophaga psenes, 2n = 12, the pollinator of F. carica, of subgenus Ficus). In this paper, we used a modified technique to analyze the karyology of three Ceratosolen species, Ceratosolen solmsi, C. graveli and C. emarginatus which are associated with figs of Ficus subgenus Sycomorus. Their karyotypes are 2n = 10. All the chromosomes are metacentric (NF = 20) with little difference in relative lengths, making them hard to distinguish. The variation in chromosome numbers that we have detected suggests that karyology can usefully complement molecular-based studies of the phylogeny of fig wasps.     

Spatial and Temporal Genetic Variation of Green Mussel, Perna viridis in the Gulf of Thailand and Implication for Aquaculture

The culture of green mussel (Perna viridis) in the Gulf of Thailand depends on natural spat which are believed to come from spawning grounds adjacent to major river mouths. In the present paper, genetic diversity of spatial and temporal populations of green mussel in the Gulf of Thailand was investigated using five microsatellite loci. The results showed moderate genetic variation of all 11 populations (averaged number of alleles per locus, A = 10.4–12.2; effective number of alleles per locus, A _e = 5.36–6.59; mean allelic richness, A _r = 10.23–12.06; observed heterozygosity, H _o = 0.52–0.63, and expected heterozygosity, H _e = 0.66–0.73) without significant differences among populations. No sign of bottleneck or genetic disequilibrium was observed. Genetic differentiation among spatial populations was low (F _ST = 0.0046, CI_0.95 = 0.0020–0.0083 for the samples collected in January, 2007, and F _ST = 0.0088, CI_0.95 = 0.0010–0.0162 for the samples collected in July, 2007) while temporal variation was significant as revealed by the analysis of molecular variance. Multidimensional scaling separated temporal population groups with minor exception. The assignment test revealed that most of the recruits were from other populations.     

Microsatellites in Cassava (Manihot esculenta Crantz): discovery, inheritance and variability

 Fourteen microsatellites containing GA-repeats were isolated and characterized in cassava (Manihot esculenta Crantz, Euphorbiaceae). Microsatellite heterozygosity (h) was estimated in 48 accessions using (³²P)-end-labeled primers and in more than 500 accessions using fluorescence-based genotyping. Heterozygosity values ranged from 0.00 to 0.88 and the number of alleles detected varied from 1 to 15. The reproducibility of allele sizing was also assessed using fluorescence-based genotyping. The average inter-gel size difference was 1.03 nucleotides. Chi-square tests (χ²) were performed to analyse segregation distortion and the linkage between alleles segregating from either or both parents in an F₁ mapping population. Most microsatellite loci segregated in the expected 1 : 1, 1 : 2 : 1 or 1 : 1 : 1 : 1 ratio. Linkage was detected between loci segregating from either parent, and segregation distortion from the male parent was detected for locus GA-131. Approximately 80% of the microsatellites detected one or two alleles per accession, suggesting a low degree of microsatellite locus duplication, an unexpected finding for a putative allopolyploid, highly heterozygous species. The high h values of most microsatellites, their amplification in other Manihot taxa and their suitability for high-throughput, fluorescence-based genotyping, make microsatellites the marker of choice for germplasm characterization and saturation of the cassava map. Received: 4 September 1997 / Accepted 16 March 1998     

QTL analysis of leaf morphology in tetraploid Gossypium (cotton)

Molecular markers were used to map and characterize quantitative trait loci (QTLs) determining cotton leaf morphology and other traits, in 180 F₂ plants from an interspecific cross between a Gossypium hirsutum genotype carrying four morphological mutants, and a wild-type Gossypium barbadense. The prominent effects of a single region of chromosome 15, presumably the classical ”Okra-leaf” locus, were modified by QTLs on several other chromosomes affecting leaf size and shape. For most traits, each parent contained some alleles with positive effects and others with negative effects, suggesting a large potential for adapting leaf size and shape to the needs of particular production regimes. Twenty one QTLs/loci were found for the morphological traits at LOD≥3.0 and P≤0.001, among which 14 (63.6%) mapped to D-subgenome chromosomes. Forty one more possible QTLs/loci were suggested with 2.0≤LOD<3.0 and 0.001<P≤0.01. Among all of the 62 possible QTLs (found at LOD≥2.0 and P≤0.01) for the 14 morphological traits in this study, 38 (61.3%) mapped to D-subgenome chromosomes. This reinforces the findings of several other studies in suggesting that the D-subgenome of tetraploid cotton has been subject to a relatively greater rate of evolution than the A-subgenome, subsequent to polyploid formation. Received: 26 April 1999 / Accepted: 30 July 1999     

Genetic structure of introduced European fallow deer (<Emphasis Type="Italic">Dama dama dama</Emphasis>) in Tasmania,Australia

European fallow deer are an introduced species classified as partly protected wildlife in Tasmania, Australia. Current management practices are primarily governed under the Quality Deer Management regime, in which animals are harvested during designated hunting seasons. Among populations, prominent morphological differences have been reported; however, the genetic relationship of these populations has until now been poorly understood. Representative animals were sampled from three key areas across their range and genotyped at ten polymorphic microsatellite loci to investigate genetic diversity, population structure, and genetic bottlenecks. Allelic richness was low in all three populations and ranged between 2.20 and 2.49 alleles/locus. A genetic bottleneck was detected in two of the three populations (P < 0.001). Population differentiation was evident between Lake Echo and Benham (q = 0.122; P < 0.001) and Benham and Connorville (q = 0.110; P < 0.001), but not between Lake Echo and Connorville (q = 0.0235), with individuals being identified as belonging to two genetic clusters. The pattern of population differentiation from the three study populations suggests that deer from the western region of their range are genetically distinct to those from the eastern region. This correlates with morphological variation within Tasmanian fallow deer, in which differences between the regions maybe attributable to geographical barriers.     

Polymorphic genotypes of the HRES-1 human endogenous retrovirus locus correlate with systemic lupus erythematosus and autoreactivity

 Antinuclear autoantibodies are a hallmark of systemic lupus erythematosus (SLE). Autoantibodies to HRES-1/p28, a 28 000 M _r nuclear protein, commonly occur in patients with SLE. HRES-1 is a single-copy endogenous retroviral element mapped to human Chromosome 1 at q42. A polymorphic Hin dIII site defines two different allelic forms of the genomic locus. The HRES-1/1 probe [5.5 kilobases (kb)] anneals to three polymorphic fragments and three genotypes can be differentiated: I, 5.5 kb fragment only; II, 3.7 kb and 1.8 kb fragments only; and III, all three polymorphic fragments. By cloning of the HRES-1 locus from homozygous type I and type II human DNA samples, the polymorphic Hin dIII site was identified as a G to C transition at position 653 of the long terminal repeat region. Family studies showed that Hin dIII genotypes of the HRES-1 locus are inherited in a Mendelian pattern. The relative frequency of genotype I with respect to genotype III was 3.1-fold lower in patients with SLE (14 : 40=0.35) in comparison to 100 ethnically matched control donors (47 : 43=1.09;P=0.0084). Frequency of genotype I vs genotype II alleles was lower in SLE (68/52) than in normal donors (137/63;P=0.033), suggesting that a genotype I allele of the HRES-1 locus may be protective against SLE. Western blot seroreactivity with recombinant HRES-1/p28 was noted in 4/14 (29%) of genotype I patients and 13/19 (68%) of genotype III patients (P<0.025). These data raise the possibility that the HRES-1 element or a gene in linkage disequilibrium with this genomic locus may influence autoimmunity in SLE. Received: 20 February 1999 / Revised: 15 April 1999     

Polymorphic microsatellites in the Reeves's pheasant developed by cross-species amplification

Cross-species microsatellite amplification is an effective way of obtaining microsatellite loci for closely related taxa in bird species. The Reeves's pheasant, Syrmaticus reevesii, is a vulnerable species endemic to China. To improve population genetics and parentage analysis studies in this species, we obtained nine polymorphic microsatellite markers, in addition to the nine markers previously isolated, from the cross-species amplification of 52 markers. The number of alleles per locus varied between two and 12 with expected heterozygosity ranging from 0.298 to 0.714 (n = 107). The success rates of simulated paternity tests using CERVUS software improved at different confidence levels after adding these markers to the previous ones.     

High levels of genetic divergence and inbreeding in populations of cupuassu (Theobroma grandiflorum)

Theobroma grandiflorum (cupuassu) is an important fruit tree native to the Brazilian Amazon. Establishing the genetic diversity and structure of populations is critical to define long-term strategies for cupuassu conservation presently threatened by rapid deforestation. Three natural populations collected at the putative center of diversity, three groups of accessions established at a germplasm collection, and one derived from commercial plantings were analyzed. The genetic diversity was assessed using 21 polymorphic microsatellite loci originally developed for Theobroma cacao, disclosing a total of 113 alleles. The estimated genetic diversity parameters averaged over cupuassu populations (A = 3.53 alleles per locus; H _e = 0.426; H _o = 0.346) were lower than the values reported for other Neotropical tree species. The three natural populations presented a positive and significant fixation index (f), ranging from 0.133 to 0.234. Cupuassu apparently adhered to a general pattern of genetic diversity structure of some Neotropical tree species occurring at low densities, with a low intrapopulation genetic diversity and important levels of endogamy, possibly due to biparental inbreeding derived from the presence of spatial genetic structure in the populations. A high level of genetic divergence was detected among the natural populations (θ _p = 0.301), a strong differentiation caused by limited gene flow, and suggesting that human interference in spreading and/or stimulating plantings might have had a smaller effect than expected. The approximate location of the T. grandiflorum center of diversity could not be confirmed by analyzing natural populations from the putative region.     

A major influence of sex-specific loci on alcohol preference in C57Bl/6 and DBA/2 inbred mice

C57Bl/6 mice reproducibly prefer to ingest more 10% ethanol in a two-bottle choice paradigm than do DBA/2J mice. In this paper we report the identification of two new sex-specific alcohol preference (Alcp) loci. Melo and associates (1996) identified two loci: Alcp1, a male-specific locus on Chromosome (Chr) 2, and Alcp2, a female- and cross-specific locus on Chr 11. We have additionally identified Alcp3, a male-specific locus on Chr 3, and Alcp4, a female-specific locus on Chr 1. We have also performed a statistical analysis to exclude the possibility of undiscovered major alcohol preference loci that are not sex-specific in our backcross paradigm. Our results indicate that alcohol preference in C57BL/6 mice, as measured in our backcross, is largely controlled in a sex-specific manner. Received: 15 September 1998 / Accepted: 8 October 1998     

Allozyme variation and divergence in the phyllotine rodent Calomys hummelincki (Husson, 1960)

The aim of the present study was to assess the degree of genetic variation and divergence among six populations of Calomys hummelincki, a phyllotine rodent distributed in northern South America. With this information we will try to evaluate the two hypotheses of possible colonization and differentiation of this group of rodents postulated by Baskin and Reig. We studied 34 loci by electrophoretic analysis: 21 were monomorphic for all populations and 13 were polymorphic in at least one population, being P _1% = 21.6% the mean value for all populations. The mean value of heterozygosity per locus was H = 0.075. Low values of genetic distance were observed among populations of the Llanos region (0.001 < D < 0.006). There was a larger genetic distance (D = 0.024) between the population from Isiro, in the northwestern semiarid region, and those from the Llanos region. The insular population of Aruba displayed the lowest value of genetic distance with the population from Isiro (D = 0.014). The specimens from Sipao, on the right side of the Orinoco river, displayed the highest values of genetic distances in comparison with other populations of C. hummelincki (0.070 < D < 0.095). The relatively high differentiation was due to the fixation of new alleles, not found in other populations of C. hummelincki, at loci Idh-1 and Est-2. F-statistics and Nm values indicated reduced gene flow among the populations sampled. Despite the limited data, the results seem to support Reig's hypothesis about south to north colonization of genus Calomys in South America. This revised version was published online in July 2006 with corrections to the Cover Date.     

A genetic linkage map of durum wheat

 A genetic linkage map of tetraploid wheat [Triticum turgidum (L.) Thell.] was constructed using segregation data from a population of 65 recombinant inbred lines (RILs) derived from a cross between the durum wheat cultivar Messapia and accession MG4343 of T. turgidum (L.) Thell. ssp dicoccoides (Korn.) Thell. A total of 259 loci were analysed, including 244 restriction fragment length polymorphisms (RFLPs), one PCR (polymerase chain reaction) marker (a sequence coding for a LMW (low-molecular-weight) glutenin subunit gene located at the Glu-B3 locus), seven biochemical (six seed-storage protein loci and one isozyme locus) and seven morphological markers. A total of 213 loci were mapped at a LOD≥3 on all 14 chromosomes of the A and B genomes. The total length of the map is 1352 cM and the average distance between adjacent markers is 6.3 cM. Forty six loci could not be mapped at a LOD≥3. A fraction (18.6%) of the markers deviated significantly from the expected Mendelian ratios; clusters of loci showing distorted segregation were found on chromosomes 1B, 3AL, 4AL, 6AL and 7AL. The durum wheat map was compared with the published maps of bread wheat using several common RFLP markers and general features are discussed. The markers detected the known structural rearrangements involving chromosomes 4A, 5A and 7B as well as the translocation between 2B-6B, but not the deletion on 2BS. This map provides a useful tool for analysing and breeding economically important quantitative traits and for marker-assisted selection, as well as for studies of genome organisation in small grain cereal species. Received: 5 January 1998 / Accepted: 31 March 1998     

Genome-wide linkage and peak-wide association study of obesity-related quantitative traits in Caribbean Hispanics

Although obesity is more prevalent in Hispanics than non-Hispanic whites in the United States, little is known about the genetic etiology of the related traits in this population. To identify genetic loci influencing obesity in non-Mexican Hispanics, we performed a genome-wide linkage scan in 1,390 subjects from 100 Caribbean Hispanic families on six obesity-related quantitative traits: body mass index (BMI), body weight, waist circumference, waist-to-hip ratio, abdominal and average triceps skinfold thickness after adjusting for significant demographic and lifestyle factors. We then carried out an association analysis of the linkage peaks and the FTO gene in an independent community-based Hispanic subcohort (N = 652, 64% Caribbean Hispanics) from the Northern Manhattan Study. Evidence of linkage was strongest on 1q43 with multipoint LOD score of 2.45 (p = 0.0004) for body weight. Suggestive linkage evidence of LOD > 2.0 was also identified on 1q43 for BMI (LOD = 2.03), 14q32 for abdominal skinfold thickness (LOD = 2.17), 16p12 for BMI (LOD = 2.27) and weight (LOD = 2.26), and 16q23–24 for average triceps skinfold thickness (LOD = 2.32). In the association analysis of 6,440 single nucleotide polymorphisms (SNPs) under 1-LOD unit down regions of our linkage peaks on chromosome 1q43 and 16p12 as well as in the FTO gene, we found that two SNPs (rs6665519 and rs669231) on 1q43 and one FTO SNP (rs12447427) were significantly associated with BMI or body weight after adjustment for multiple testing. Our results suggest that in addition to FTO, multiple genetic loci, particularly those on 1q43 region, may contribute to the variations in obesity-related quantitative traits in Caribbean Hispanics.     

Regulation of adiponectin gene expression in adipose tissue by thyroid hormones

Available experimental data suggest that adiponectin and thyroid hormones have biological interaction in vivo. However, the effects of thyroid hormones on adipose adiponectin gene expression in thyroid dysfunction are unclear. We induced hyper- (HYPER) and hypothyroidism (HYPO) by daily administration of a 12 mg/l of levothyroxine and 250 mg/l of methimazole in drinking water of rats, respectively, for 42 days. The white adipose tissues and serum sample were taken on days 15, 28, 42 and also 2 weeks after treatment cessation. Analysis of adiponectin gene expression was performed by real-time PCR and 2^−ΔΔct method. The levels of adipose tissue adiponectin mRNA in the HYPO rats were decreased during the 6-week treatment when compared to control rats (<0.05) and were increased significantly 2 weeks after HYPO cessation (P < 0.05). This decline in adiponectin gene expression occurred in parallel with a decrease in T3, T4, fT3 and fT4 concentrations (P < 0.05). In opposite to HYPO rats, adipose adiponectin gene expression was increased in HYPER rats during the 6-week treatment in parallel with an increase the thyroid hormones concentrations (P < 0.05), and its expression was decreased 2 weeks after HYPER cessation (P < 0.05). Adiponectin gene expression levels showed significant negative correlations with concentrations of LDL (HYPO; r = −0.806, P = 0.001 and HYPER; r = −0.749, P = 0.002), triglyceride (HYPO; r = −0.825, P = 0.001 and HYPER; r = −0.824, P = 0.001) and significant positive correlations with concentrations of glucose (HYPO; r = 0.674, P = 0.004 and HYPER; r = 0.866, P = 0.001) and HDL (HYPO; r = 0.755, P = 0.001 and HYPER; r = 0.839, P = 0.001). The current study provides evidence that adiponectin gene expression in adipose tissue is regulated by thyroid hormones at the translation level and that lipid and carbohydrate disturbances in a patient with thyroid dysfunction may be, in part, due to adiponectin gene expression changes.     

Genetic control of aluminium tolerance in rye (Secale cereale L.)

 Aluminium (Al) tolerance in roots of two cultivars (“Ailés” and “JNK”) and two inbred lines (“Riodeva” and “Pool”) of rye was studied using intact roots immersed in a nutrient solution at a controlled pH and temperature. Both the cultivars and the inbred lines analysed showed high Al tolerance, this character being under multigenic control. The inbred line “Riodeva” was sensitive (non-telerant) at a concentration of 150 μM, whereas the “Ailes” cultivar showed the highest level of Al tolerance at this concentration. The segregation of aluminium-tolerance genes and several isozyme loci in different F₁s, F₂s and backcrosses between plants of “Ailés” and “Riodeva” were also studied. The segregation ratios obtained for aluminium tolerance in the F₂s analysed were 3 : 1 and 15 : 1 (tolerant : non-tolerant) while in backcrosses they were 1 : 1 and 3 : 1. These results indicated that Al tolerance is controlled by, at least, two major dominant and independent loci in rye (Alt1 and Alt3). Linkage analyses carried out between Al-tolerance genes and several isozyme loci revealed that the Alt1 locus was linked to the aconitase-1 (Aco1), nicotinamide adenine dinucleotide dehydrogenase-2 (Ndh2), esterase-6 (Est6) and esterase-8 (Est8) loci, located on chromosome arm 6RL. The order obtained was Alt1-Aco1-Ndh2-Est6-Est8. The Alt3 locus was not linked to the Lap1, Aco1 and Ndh2 loci, located on chromosome arms, 6RS, 6RL and 6RL respectively. Therefore, the Alt3 locus is probably on a different chromosome. Received: 18 March 1997 / Accepted: 21 March 1997     

A first set of gene-derived polymorphic microsatellite markers in half-smooth tongue sole (<Emphasis Type="Italic">Cynoglossus semilaevis</Emphasis>)

Half-smooth tongue sole (Cynoglossus semilaevis) is a commercially important marine fish species in China. A set of type I microsatellite markers were identified through bioinformatic mining of the GenBank database. Thirteen of these markers showed polymorphisms through genotyping a sample of 30 individuals. A total of 47 alleles were detected, with an average of 3.6 alleles per locus. The number of alleles, observed and expected heterozygosity per locus ranged from two to five, from 0.14 to 0.93 and from 0.27 to 0.77, respectively. Three loci significantly deviated from Hardy-Weinberg equilibrium after Bonferroni correction (P < 0.0038) and no significant linkage disequilibrum between pairs of loci was found. The markers identified in this study will contribute to construction of genetic linkage maps and mapping of quantitative trait loci (QTL) of C. semilaevis.     

Search for nucleotide diversity patterns of local adaptation in dehydrins and other cold-related candidate genes in Scots pine (Pinus sylvestris L.)

Nucleotide variation at several cold candidate genes including seven members of the dehydrin gene family was surveyed in haplotypes of Scots pine (Pinus sylvestris) sampled in populations showing divergence for cold tolerance in Europe. Patterns of nucleotide diversity, linkage disequilibrium, and frequency spectrum of alleles were compared between north and south populations to search for signs of directional selection potentially underlying adaptation to cold. Significant differentiation between populations in allelic frequency or haplotype structure was detected at dhn1, dhn3, and abaH loci. Allelic dimorphism with no evidence of haplotype clustering by geographical distribution was found at dhn9. An excess of fixed non-synonymous mutations as compared to the outgroup P. pinaster pine species was found at dhn1. Differences in nucleotide polymorphisms were found between the members of the Kn class of dehydrin upregulated during cold acclimation (average π_sil = 0.004) as compared to the SKn class (average π_sil = 0.024). The multilocus nucleotide diversity at silent sites (θ _W = 0.009) was moderate compared to other conifer species, but higher than previous estimates for Scots pine. There was an excess of rare and high frequency derived variants as revealed by significantly negative multilocus value of Tajima’s D (D = −0.72, P < 0.01) and negative mean value of Fay and Wu H statistics (H = −0.50). The level of linkage disequilibrium decayed rapidly with an average expected r ² of 0.2 at about 200 bp. Overall, there was a positive correlation between polymorphism and divergence at ten loci when outgroup sequence was available. The discovered polymorphism will be used for further evaluation of the adaptive role of genes through association mapping studies. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Short-distance pollen dispersal and high self-pollination in a bat-pollinated neotropical tree

We investigated pollen dispersal and breeding structure in the tropical tree species Caryocar brasiliense Camb. (Caryocaraceae), using genetic data from ten microsatellite loci. All adult trees (101) within a patch of 8.3 ha were sampled, and from these adults 18 open-pollinated maternal progeny arrays were analyzed (280 seeds from 265 fruits). Most fruits presented only one seed (median equal to 1.000) and mean number of ripened seeds per fruit was 1.053 (SD = 0.828). Our results showed that C. brasiliense presents a mixed-mating system, with 11.4% of self-pollination, multilocus outcrossing rate of t _m = 0.891 ± 0.025, and high probability of full-sibship within progeny arrays (r _p = 0.135 ± 0.032). Outcrossing rate and self-pollination varied significantly among mother trees. We could detect a maximum pollen dispersal distance of ∼500 m and a mean pollen dispersal distance of ∼132 m. However, most pollination events (80%) occurred at distances less than 200 m. Our results also indicated that pollen dispersal is restricted to a neighborhood of 5.4 ha with rare events of immigration (∼1% N _e m = 0.35). C. brasiliense also presents a significant but weak spatial genetic structure (Sp = 0.0116), and extension of pollen dispersal distance was greater than seed dispersal (N _b = 86.20 m). These results are most likely due to the foraging behavior of pollinators that may have limited flight range. The highly within-population synchronous flowering, high population density, and clumped distribution reinforce pollinator behavior and affect residence time leading to a short-distance pollen dispersal.     

Genetic variation in pea (Pisum) dehydrins: sequence elements responsible for length differences between dehydrin alleles and between dehydrin loci in Pisum sativum L.

 The electrophoretic patterns of dehydrins extracted from mature seeds of a range of pea (Pisum) species revealed extensive variation in dehydrin polypeptide mobility. Variation was also observed among lines of P. sativum. Crosses between lines with different dehydrin electrophoretic patterns produced F₁ seeds with additive patterns, and segregation in the F₂ generation was consistent with a 1 : 2 : 1 ratio, indicating allelic variation at each of two dehydrin loci (Dhn2, Dhn3). Genetic linkage was observed between Dhn2 and Dhn3, and the segregation ratios indicated preferential transmission of one allele at the Dhn3 locus. Dehydrin cDNA clones were characterised that encoded the allelic variants at Dhn2 and Dhn3. Their deduced amino-acid sequences were very similar to each other as well as to the product of the Dhn1 locus reported previously. Comparisons were made between the sequences of allelic variants at a single locus, and between the products of different loci. Differences in the electrophoretic mobilities between allelic variants at Dhn2 and Dhn3 were associated with differences in polypeptide length resulting principally from tandem duplications of 21 (Dhn2) or 24 (Dhn3) amino-acid residues. These duplications accounted for much of the difference in length between dehydrins encoded by the different loci. The conserved core of one of the duplicated regions varied in copy number, and small insertions/deletions of amino acids near this core also contributed to length variation both between allelic forms and between loci. Dehydrins possess characteristic highly conserved amino-acid sequence motifs, yet vary considerably in length. Mechanisms involving sequence duplication appear to be responsible for generating the length differences observed between allelic variants as well as between the products of different loci. Received: 12 June 1997 / Accepted: 29 October 1997