Glucocorticosteroid-induced osteoporosis in adult primiparous Göttingen miniature pigs: effects on bone mineral and mineral metabolism

Information on the pathophysiology of glucocorticoid-induced osteoporosis (GIO) is limited, since its clinical picture often reflects a combined effect of glucocorticoids (GC) and the treated systemic disease (i.e., inflammation and immobility). In 50 healthy adult (30-mo-old) primiparous G?ttingen minipigs, we studied the short-term (8 mo, n = 30) and long-term (15 mo, n = 10) effect of GC on bone and mineral metabolism longitudinally and cross-sectionally compared with a control group (n = 10). All animals on GC treatment received prednisolone orally at a dose of 1.0 mg x kg body wt(-1) x day(-1) for 8 wk and thereafter at 0.5 mg/kg body wt(-1) x day(-1). In the short term, GC reduced bone mineral density (BMD) at the lumbar spine by -47.5 +/- 5.1 mg/cm(3) from baseline (P < 0.001), which was greater (P < 0.05) than the loss [not significant (NS)] in the control group of -11.8 +/- 12.6 mg/cm(3). Calcium absorption decreased from baseline by -2,488 +/- 688 mg/7 days (P < 0.001) compared with -1,380 +/- 1,297 mg/7 days (NS) in the control group. Plasma bone alkaline phosphatase (BAP) decreased from baseline by -17.8 +/- 2.2 U/l (P < 0.000), which was significantly different (P < 0.05) from the value of the control group of -1.43 +/- 4.8 U/l. In the long term, the loss of BMD became more pronounced and bone mineral content (BMC), trabecular thickness, mechanical stability, calcium absorption, 25-hydroxyvitamin D(3), 1,25-dihydroxyvitamin D(3), and parathyroid hormone tended to be lower compared with the control group. There was a negative association between the cumulative dose of GC and BMD, which was associated with impaired osteoblastogenesis. In conclusion, the main outcomes after GC treatment are comparable to symptoms of GC-induced osteoporosis in human subjects. Thus the adult G?ttingen miniature pig appears to be a valuable animal model for GC-induced osteoporosis.     

Development and integration of EST–SSR markers into an established linkage map in switchgrass

Switchgrass (Panicum virgatum L.) is a model cellulosic biofuel crop in the United States. Simple sequence repeat (SSR) markers are valuable resources for genetic mapping and molecular breeding. A large number of expressed sequence tags (ESTs) of switchgrass are recently available in our sequencing project. The objectives of this study were to develop new SSR markers from the switchgrass EST sequences and to integrate them into an existing linkage map. More than 750 unique primer pairs (PPs) were designed from 243,600 EST contigs and tested for PCR amplifications, resulting in 538 PPs effectively producing amplicons of expected sizes. Of the effective PPs, 481 amplifying informative bands in NL94 were screened for polymorphisms in a panel consisting of NL94 and its seven first-generation selfed (S1) progeny. This led to the selection of 117 polymorphic EST–SSRs to genotype a mapping population encompassing 139 S1 individuals of NL94. Of 83 markers demonstrating clearly scorable alleles in the mapping population, 79 were integrated into a published linkage map, with three linked to accessory loci and one unlinked. The newly identified EST–SSR loci were distributed in 17 of 18 linkage groups with 27 (32.5 %) exhibiting distorted segregations. The integration of EST–SSRs aided in reducing the average marker interval (cM) to 3.7 from 4.2, and reduced the number of gaps (each >15 cM) to 10 from 23. Developing new EST–SSRs and constructing a higher density linkage map will facilitate quantitative trait locus mapping and provide a firm footing for marker-assisted breeding in switchgrass.     

Diurnal variation and age-related changes of bone turnover markers in female Göttingen minipigs

We investigated diurnal variation and age-related changes in bone turnover markers in female Gottingen minipigs. Ten females, 6-9 months of age, were used for confirmation of diurnal variation. Blood was collected at 3 h intervals for 24 h, and bone-specific alkaline phosphatase and intact osteocalcin (OC) levels were determined by enzyme immunoassay and radioimmunoassay, respectively. Urine was collected at 3 h intervals for 24 h using a tray attached to the bottom of the cage. The levels of N-terminal telopeptide of type I collagen (NTX) were determined by enzyme immunoassay. Pyridinoline and deoxypyridinoline were measured by high performance liquid chromatography. OC and NTX exhibited diurnal variation (Kruskal-Wallis test, P < 0.05), with the highest and lowest levels at 18:00 h (76.7 +/- 26.2 ng/ml) and 06:00 h (44.3 +/- 10.3 ng/ml), and at 03:00-05:59 h (550.4 +/- 82.4 nmol/micromol Cr) and 12:00-14:59 h (297.8 +/- 152.5 nmol/micromol Cr), respectively. In the study of age-related changes, blood and urine samples from 66 females (age range, 3-76 months) were examined to determine the bone turnover markers. All markers showed high correlations with age (0.569 < R(2) < 0.818). High levels of bone turnover markers were observed in young animals, decreasing with age (Kruskal-Wallis test, P < 0.01). The diurnal variation and age-related changes revealed in the present study will be useful in studies of bone diseases using female Gottingen minipigs.     

Regression of diet-induced atherosclerosis in G?ttingen miniature swine

The regression of diet-induced atherosclerosis in G?ttingen Miniature Swine was investigated after a 6-month induction period. At 1 month after feeding a high-cholesterol and high-fat diet, levels of beta-lipoprotein, total cholesterol, free fatty acids and phospholipid had increased rapidly and the high levels were maintained throughout the 6 month induction period. Morphological features at 6 months showed fatty streaks in the thoracic aorta and fibrous plaques in the abdominal aorta. After return to the conventional diet at 6 months, serum lipids decreased rapidly and maintained the baseline level throughout the 9 month regression period. Histopathological findings showed the regression of fatty streaks but the fibrous plaques did not regress. The present study therefore confirms the regression of fatty streaks in the aorta of G?ttingen Miniature Swine by the administration of a cholesterol lowering diet.     

Analysis of recessive lethality on swine chromosome 6 in a Göttingen miniature resource family

Previously, we reported recessive gene(s) that terminate fetal development on swine chromosome (SSC) 6 between SW855 and SW122. The affected alleles originated from a Göttingen miniature pig used for construction of a Göttingen miniature pig × Meishan resource population. However, it is not known when the gene(s) are activated during fetal development, which is one of the important factors in selecting candidate genes responsible for fetal death. In the present study, a second swine population consisting of 159 progeny was produced by mating pigs carrying the deleterious allele(s). This population allowed us to narrow the genetic region harbouring the affected gene(s) and to demonstrate that the region was confined between RYR1 and SW782 (5.7 cM on the National Institute of Animal Industry (NIAI) map and 100 cR on the INRA/University of Minnesota porcine radiation hybrid panel map). In order to determine when the affected gene(s) are activated and in turn terminate fetal development, embryos produced in the second population were collected at several development stages and genotyped for markers in the region. Genes in the homozygous state affected embryo development between 9 and 11 days post‐coitus.     

Exploitation of pepper EST–SSRs and an SSR-based linkage map

As genome and cDNA sequencing projects progress, a tremendous amount of sequence information is becoming publicly available. These sequence resources can be exploited for gene discovery and marker development. Simple sequence repeat (SSR) markers are among the most useful because of their great variability, abundance, and ease of analysis. By in silico analysis of 10,232 non-redundant expressed sequence tags (ESTs) in pepper as a source of SSR markers, 1,201 SSRs were found, corresponding to one SSR in every 3.8 kb of the ESTs. Eighteen percent of the SSR–ESTs were dinucleotide repeats, 66.0% were trinucleotide, 7.7% tetranucleotide, and 8.2% pentanucleotide; AAG (14%) and AG (12.4%) motifs were the most abundant repeat types. Based on the flanking sequences of these 1,201 SSRs, 812 primer pairs that satisfied melting temperature conditions and PCR product sizes were designed. 513 SSRs (63.1%) were successfully amplified and 150 of them (29.2%) showed polymorphism between Capsicum annuum ‘TF68’ and C. chinense ‘Habanero’. Dinucleotide SSRs and EST–SSR markers containing AC-motifs were the most polymorphic. Polymorphism increased with repeat length and repeat number. The polymorphic EST–SSRs were mapped onto the previously generated pepper linkage map, using 107 F₂ individuals from an interspecific cross of TF68 × Habanero. One-hundred and thirtynine EST–SSRs were located on the linkage map in addition to 41 previous SSRs and 63 RFLP markers, forming 14 linkage groups (LGs) and spanning 2,201.5 cM. The EST–SSR markers were distributed over all the LGs. This SSR-based map will be useful as a reference map in Capsicum and should facilitate the use of molecular markers in pepper breeding.Gibum Yi and Je Min Lee equally contributed to this work.     

QTL analysis of clinical-chemical traits in an F₂ intercross between Landrace and Korean native pigs

Clinical-chemical traits are essential when examining the health status of individuals. The aim of this study was to identify quantitative trait loci (QTL) and the associated positional candidate genes affecting clinical-chemical traits in a reciprocal F(2) intercross between Landrace and Korean native pigs. Following an overnight fast, 25 serum phenotypes related to clinical-chemical traits (e.g., hepatic function parameters, renal function parameters, electrolyte, lipids) were measured in >970 F(2) progeny. All experimental samples were subjected to genotyping analysis using 165 microsatellite markers located across the genome. We identified eleven genome-wide significant QTL in six chromosomal regions (SSC 2, 7, 8, 13, 14, and 15) and 59 suggestive QTL in 17 chromosomal regions (SSC 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 13, 14, 15, 16, 17, and 18). We also observed significant effects of reciprocal crosses on some of the traits, which would seem to result from maternal effect, QTL on sex chromosomes, imprinted genes, or genetic difference in mitochondrial DNA. The role of genomic imprinting in clinical-chemical traits also was investigated. Genome-wide analysis revealed a significant evidence for an imprinted QTL in SSC4 affecting serum amylase levels. Additionally, a series of bivariate linkage analysis provided strong evidence that QTL in SSC 2, 13, 15, and 18 have a pleiotropic effect on clinical-chemical traits. In conclusion, our study detected both novel and previously reported QTL influencing clinical-chemical traits in pigs. The identified QTL together with the positional candidate genes identified here could play an important role in elucidating the genetic structure of clinical-chemical phenotype variation in humans and swine.     

Measurements of insulin responses as predictive markers of pancreatic beta-cell mass in normal and beta-cell-reduced lean and obese Göttingen minipigs in vivo

At present, the best available estimators of beta-cell mass in humans are those based on measurement of insulin levels or appearance rates in the circulation. In several animal models, these estimators have been validated against beta-cell mass in lean animals. However, as many diabetic humans are obese, a correlation between in vivo tests and beta-cell mass must be evaluated over a range of body weights to include different levels of insulin sensitivity. For this purpose, obese (n = 10) and lean (n = 25) G?ttingen minipigs were studied. Beta-cell mass had been reduced (n = 16 lean, n = 5 obese) with a combination of nicotinamide (67 mg/kg) and streptozotocin (125 mg/kg), acute insulin response (AIR) to intravenous glucose and/or arginine was tested, pulsatile insulin secretion was evaluated by deconvolution (n = 30), and beta-cell mass was determined histologically. AIR to 0.3 (r(2) = 0.4502, P < 0.0001) or 0.6 g/kg glucose (r(2) = 0.6806, P < 0.0001), 67 mg/kg arginine (r(2) = 0.5730, P < 0.001), and maximum insulin concentration (r(2) = 0.7726, P < 0.0001) were all correlated to beta-cell mass when evaluated across study groups, and regression lines were not different between lean and obese groups except for AIR to 0.3 g/kg glucose. Baseline pulse mass was not significantly correlated to beta-cell mass across the study groups (r(2) = 0.1036, NS), whereas entrained pulse mass did show a correlation across groups (r(2) = 0.4049, P < 0.001). This study supports the use of in vivo tests of insulin responses to evaluate beta-cell mass over a range of body weights in the minipig. Extensive stimulation of insulin secretion by a combination of glucose and arginine seems to give the best correlation to beta-cell mass.     

Quantitative trait loci (QTL) analysis in a Meishan x Göttingen cross population

In order to locate the genetic regions in the swine genome that are responsible for economically important traits, a resource population has been constructed by mating two female Meishan pigs with a male Göttingen miniature pig. In subsequent generations, 265 F2 offspring were produced from two F1 males and 19 F1 females. The F2 offspring were scored for eight traits including growth rate, teat number, vertebra number and backfat thickness, and genotyped for 318 genetic markers spanning the swine genome. Least‐square analysis revealed quantitative trait loci (QTL) effects for vertebra number on chromosomes 1 and 2; for teat number on chromosomes 1 and 7; for birth weight on chromosome 1; for average daily gain between 4 and 13 weeks of age on chromosomes 9 and 10; for backfat thickness on chromosome 7; and for backskin thickness on chromosome 3.     

New genetic map of rye composed of PCR-based molecular markers and its alignment with the reference map of the DS2 × RXL10 intercross

A new genetic map of rye, developed by using the 541 x Ot1-3 F2 intercross, consists of 148 marker loci, including 99 RAPDs, 18 SSRs, 14 STSs, 9 SCARs and 7 ISSRs, and spans the distance of 1401.4 cM. To the 7 rye chromosomes, 8 linkage groups were assigned and compared with the reference map of the DS2 x RXL10 F2 intercross by using 24 common markers. The 2 combined maps contain altogether 611 marker loci (70-109 per chromosome) and constitute a substantial source of information useful for further genomic studies in rye. From 21 to 37 RAPD marker loci are distributed randomly along each chromosome length and their total number for all 7 rye chromosomes is 177. This abundance of RAPD marker loci in the rye genetic map can be exploited for development of SCARs in regions containing important genes or QTL.     

Latissimus dorsi cardiomyoplasty: a chronic experimental porcine model. Feasibility study of cardiomyoplasty in Danish Landrace pigs and Göttingen minipigs

Cardiomyoplasty is an experimental treatment for end-stage heart failure. We hypothesized that the porcine latissimus dorsi muscle (LDM) in an experimental porcine model is a suitable surrogate for a clinically relevant evaluation of this concept. Fourteen Danish Landrace (DL) pigs and six G?ttingen minipigs (GM) were studied. The LDM was evaluated immediately after surgical dissection and in various phases: phase 1 (n = 4)--outcome of a partial vascular isolation (vascular delay), 2 to 3 weeks prior to heart wrapping in DL pigs; phase 2 (n = 6)--long-term flap survival of nonstimulated LDM cardiomyoplasty in DL pigs; phase 3 (n = 6)--outcome of nonstimulated cardiomyoplasty in GM; phase 4--one DL pig had dynamic cardiomyoplasty performed and was subjected to low-intensity LDM stimulation for 8 months. Isolation of the LDM of DL pigs and GM as a pedicled graft had no acute deleterious impact on the global blood supply. In phase 1a, partial vascular isolation and in situ recovery of the LDM resulted in a muscle encapsulated in fibrotic tissue, which hampered a later heart wrap. In phase 1b, a less extensive dissection diminished fibrosis and allowed subsequent wrapping. In phase 2, after 6 weeks of nonstimulated LDM cardiomyoplasty, the LDM of DL pigs was viable, with excellent heart-muscle integration. In phase 3, the same procedure applied in GM yielded the same result as that in DL pigs, but with a higher success rate owing to the learning phase.     

Metabolism of peptide YY 3–36 in Göttingen mini-pig and rhesus monkey

Peptide YY 3–36-amide (PYY_3–36) is a peptide hormone, which is known to decrease appetite and food-intake by activation of the Y₂ receptor. The current studies were designed to identify the metabolites of PYY_3–36 in mini-pig and rhesus monkey. Plasma samples were analyzed by high resolution LC–MS (and MS/MS) in order to unambiguously identify the metabolites of PYY_3–36. In summary, the metabolism of PYY_3–36 was similar in mini-pig and rhesus monkey. Several metabolites were identified and PYY_3–34 was identified at the highest levels in plasma. In addition, mini-pigs were also dosed with PYY_1–36-amide, PYY_3–35, PYY_3–34 and [N-methyl 34Q]-PYY_3–36-amide in order to investigate the mechanisms by which PYY was metabolized. PYY_3–35 was rapidly converted to PYY_3–34 whereas dosing of PYY_3–34 to mini-pigs only showed circulating degradation products at low levels, i.e., PYY_3–34 was metabolically more stable than PYY_3–36 and PYY_3–35. [N-methyl 34Q]-PYY_3–36-amide was hypothesized to be stable toward cleavage between 34Q and 35R and after i.v. administration to mini-pigs, one major cleavage product was identified as [N-methyl 34Q]-PYY_3–35. Overall, this showed that cleavage between 35R and 36Y was possible as well as between 34Q and 35R (as shown for PYY_3–35), which indicated that metabolism of PYY_3–36 to PYY_3–34 may be a two-step process. PYY_1–36 was also dosed to mini-pigs, which showed that PYY_1–36 was metabolized in the C-terminal as PYY_3–36. The overall degradation pattern of PYY_1–36 was more complex due to the simultaneous enzymatic degradation in the N-terminal to form PYY_2–34/36 and PYY_3–34/36. In vitro incubations with heparin stabilized plasma showed that PYY_3–36 was degraded with a half-life of 175 min, whereas incubations with PYY_3–35 (half-life of 6 min) showed a rapid formation of PYY_3–34. In conclusion, the present studies showed that PYY_3–36 underwent enzymatic degradation in the C-terminal part and that the major circulating metabolite was PYY_3–34. Furthermore, it may be a sequential two-step process leading to the formation of PYY_3–35 and subsequently the metabolically more stable PYY_3–34.     

Mild streptozotocin diabetes in the Göttingen minipig. A novel model of moderate insulin deficiency and diabetes

Nonrodent models of diabetes are needed for practical and physiological reasons. Induction of mild insulin-deficient diabetes was investigated in male G?ttingen minipigs by use of streptozotocin (STZ) alone (75, 100, and 125 mg/kg) or 125 mg/kg combined with pretreatment with nicotinamide (NIA; 0, 20, 67, 100, 150, and 230 mg/kg). Use of NIA resulted in a less steep slope of the regression line between fasting plasma glucose and changing doses compared with STZ [-7.0 +/- 1.4 vs. 29.7 +/- 7.0 mM. mg(-1). kg(-1), P < 0.0001]. Intermediate NIA doses induced moderate changes of glucose tolerance [glucose area under the curve increased from 940 +/- 175 to 1,598 +/- 462 mM. min, P < 0.001 (100 mg/kg) and from 890 +/- 109 to 1,669 +/- 691 mM. min, P = 0.003 (67 mg/kg)] with reduced insulin secretion [1,248 +/- 602 pM. min after 16 days and 1,566 +/- 190 pM. min after 60 days vs. 3,251 +/- 804 pM. min in normal animals (P < 0.001)] and beta-cell mass [5.5 +/- 1.4 mg/kg after 27 days and 7.9 +/- 4.1 mg/kg after 60 days vs. 17.7 +/- 4.7 mg/kg in normal animals (P = 0.009)]. The combination of NIA and STZ provided a model characterized by fasting and especially postprandial hyperglycemia and reduced, but maintained, insulin secretion and beta-cell mass. This model holds promise as an important tool for studying the pathophysiology of diabetes and development of new pharmacological agents for treatment of the disease.     

Acquisition of visually guided conditional associative tasks in Göttingen minipigs

Fourteen Göttingen minipigs were trained on two different visually guided conditional associative tasks. In a spatial conditional task, a black stimulus signalled that a response to the left was correct, and a white stimulus signalled that a response to the right was correct. In a conditional go/no-go task, a blue stimulus signalled go, and a red stimulus signalled no-go. The pigs were trained until a behavioural criterion of 90% correct for each of two consecutive sessions. For the spatial conditional task, all pigs reached this criterion in 520 trials or less. For the conditional go/no-go task, all pigs, except three, reached this criterion in 1600 trials or less. Sows and boars learned equally fast. The tasks can be useful for the testing of cognitive function in pig models of human brain disorders.     

A population ‘consensus’, partial linkage map of Picea abies Karst. based on RAPD markers

 We built a “consensus” partial linkage map based on RAPD markers using 48 sibships of eight megagametophytes each from a natural population of Norway spruce. A RAPD linkage map for a single individual from the same population had previously been constructed. Using 30 random decamers that had yielded 83 RAPD markers in the single-tree map, eight megagametophytes for each of the 48 sibships were screened. The linkage relationship among markers was estimated considering each family of eight megagametophytes as a progeny of a phase-unknown backcross mating between a heterozygous mother and a fictitious ‘recessive’ father. Markers were assigned to windows using LOD=2.0 and θ=0.4 as thresholds, and ordered using a criterion of interval support ≥2.0. For eight “windows” of recombination selected on the single-tree map, we investigated the consistency of marker order in the two maps. We adopted restrictive criteria for rejecting co-linearity between the two locus orders. For each window we imposed the most likely locus order obtained from one data set to the other (and vice versa), obtaining two symmetrical log-likelihood differences. We considered the hypothesis of co-linearity rejected when both symmetrical differences were significant (ΔLOD>3.0). By bootstrapping a subset of markers for each window (highly informative, ‘framework’ loci chosen on the previous single-tree map using a matrix correlation method) the sampling variability of the single-tree and population maps was estimated. As expected the population map was affected by a larger variability than the single-tree map. Heterogeneity in pairwise recombination fractions among groups of sibship revealed a (possible) alternative genomic arrangement detected within a single recombination window. Received : 4 January 1997 / Accepted : 24 January 1997     

Discriminations, reversals, and extra-dimensional shifts in the Göttingen minipig

G?ttingen minipigs were trained on a set-shifting procedure involving discriminations, reversals, and extra-dimensional shifts. The discriminations used were black-white discriminations and right-left discriminations. The initial visual and spatial discrimination seemed equally difficult, and only for the visual modality was reversal found to be more difficult than the initial discrimination. Visual reversal was more difficult than spatial reversal, and a larger number of perseverative sessions were found for visual reversal compared to spatial reversal. The acquisition of the extra-dimensional shift from the visual to the spatial dimension was not inferior to the learning of spatial reversal. Neither was the acquisition of the extra-dimensional shift from the spatial to the visual dimension inferior to the learning of visual reversal. Thus, no evidence was found for attention to stimulus dimensions in discrimination learning of the pigs.     

Survival of Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus in the terminal ileum of fistulated Göttingen minipigs

The ability of Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus administered in yogurt to survive the passage through the upper gastrointestinal tract was investigated with G?ttingen minipigs that were fitted with ileum T-cannulas. After ingestion of yogurt containing viable microorganisms, ileostomy samples were collected nearly every hour beginning 3 h after food uptake. Living L. delbrueckii subsp. bulgaricus and S. thermophilus were detected in the magnitude of 10(6) to 10(7) per gram of intestinal contents (wet weight) in all animals under investigation. A calculation of the minimum amount of surviving bacteria that had been administered is presented. Total DNA extracted from ileostomy samples was subjected to PCR, which was species specific for L. delbrueckii and S. thermophilus and subspecies specific for L. delbrueckii subsp. bulgaricus. All three bacterial groups could be detected by PCR after yogurt uptake but not after uptake of a semisynthetic diet. One pig apparently had developed an endogenous L. delbrueckii flora. When heat-treated yogurt was administered, L. delbrueckii was detected in all animals. S. thermophilus or L. delbrueckii subsp. bulgaricus was not detected, indicating that heat-inactivated cells and their DNAs had already been digested and their own L. delbrueckii flora had been stimulated for growth.     

Construction of a SNP and SSR linkage map in autotetraploid blueberry using genotyping by sequencing

The construction of the first genetic map in autotetraploid blueberry has been made possible by the development of new SNP markers developed using genotyping by sequencing in a mapping population created from a cross between two key highbush blueberry cultivars, Draper × Jewel (Vaccinium corymbosum). The novel SNP markers were supplemented with existing SSR markers to enable the alignment of parental maps.  In total, 1794 single nucleotide polymorphic (SNP) markers and 233 simple sequence repeat (SSR) markers exhibited segregation patterns consistent with a random chromosomal segregation model for meiosis in an autotetraploid. Of these, 700 SNPs and 85 SSRs were utilized for construction of the ‘Draper’ genetic map, and 450 SNPs and 86 SSRs for the ‘Jewel’ map.  The ‘Draper’ map comprises 12  linkage groups (LG), associated with the haploid chromosome number for blueberry, and totals 1621 cM while the ‘Jewel’ map comprises 20 linkage groups totalling 1610 cM. Tentative alignments of the two parental maps have been made on the basis of shared SSR alleles and linkages to double-simplex markers segregating in both parents. Tentative alignments of the two parental maps have been made on the basis of shared SSR alleles and linkages to double-simplex markers segregating in both parents.     

An interspecific (Capsicum annuum ×C. chinese) F2 linkage map in pepper using RFLP and AFLP markers

We have constructed a molecular linkage map of pepper (Capsicum spp.) in an interspecific F₂ population of 107 plants with 150 RFLP and 430 AFLP markers. The resulting linkage map consists of 11 large (206–60.3 cM) and 5 small (32.6–10.3 cM) linkage groups covering 1,320 cM with an average map distance between framework markers of 7.5 cM. Most (80%) of the RFLP markers were pepper-derived clones, and these markers were evenly distributed across the genome. By using 30 primer combinations, we were able to generate 444 AFLP markers in the F₂ population. The majority of the AFLP markers clustered in each linkage group, although PstI/MseI markers were more evenly distributed than EcoRI/MseI markers within the linkage groups. Genes for the biosynthesis of carotenoids and capsaicinoids were mapped on our linkage map. This map will provide the basis of studying secondary metabolites in pepper. Received: 20 October 1999 / Accepted: 3 July 2000     

A smörgåsbord of markers for avian ecology and evolution

The polymerase chain reaction has been a boon to the study of molecular ecology and population genetics of birds. But the nagging truth is that for many bird species, the number of polymerase chain reaction (PCR) primer pairs that one can pick off the shelf and expect to amplify their target loci with ease is frustratingly small. Now, studying DNA sequence variation in natural populations of birds just got a whole lot easier. This issue of Molecular Ecology reports a large-scale bioinformatics search for exonic sequences conserved between the chicken and zebra finch genomes and flanking polymorphic introns that has generated a staggering 242 PCR primer pairs that readily amplify their single-copy target loci in five avian species spanning ~100 million years of avian evolution ( Backström et al . 2008 ). As proof of principle, these primers have also been used to survey the genomic landscape in over 110 kb of intronic sequence in the collared flycatcher, a model species in ecology and evolution. These resources pave the way for easy multilocus study of evolving populations and lineages of birds, and bring the goal of quickly turning nonmodel species in to ecological genomic models tantalizingly close.