MAAP: a versatile and universal tool for genome analysis

Population admixtures in medaka inferred by multiple arbitrary amplicon sequencing

Cost-effective genotyping can be achieved by sequencing PCR amplicons. Short 3-10 base primers can arbitrarily amplify thousands of loci using only a few primers. To improve the sequencing efficiency of the multiple arbitrary amplicon sequencing (MAAS) approach, we designed new primers and examined their efficiency in sequencing and genotyping. To demonstrate the effectiveness of our method, we applied it to examining the population structure of the small freshwater fish, medaka (Oryzias latipes). We obtained 2987 informative SNVs with no missing genotype calls for 67 individuals from 15 wild populations and three artificial strains. The estimated phylogenic and population genetic structures of the wild populations were consistent with previous studies, corroborating the accuracy of our genotyping method. We also attempted to reconstruct the genetic backgrounds of a commercial orange mutant strain, Himedaka, which has caused a genetic disturbance in wild populations. Our admixture analysis focusing on Himedaka showed that at least two wild populations had genetically been contributed to the nuclear genome of this mutant strain. Our genotyping methods and results will be useful in quantitative assessments of genetic disturbance by this commercially available strain.

Radiation-induced phenotypic alterations in relation to isozymes and RAPD markers inVigna radiata(L.) Wilczek

PURPOSE

The present investigation is aimed at studies on the effects of gamma rays on in vitro and in vivo damage in Vigna radiata. The parameters studied are germination frequency, seedling injury, isozyme alteration and random amplified polymorphic DNA (RAPD) markers. Results obtained are analyzed in the light of modern applications of radiation damage.

MATERIALS AND METHODS

Seeds of Vigna radiata were subjected to gamma irradiation with a dose of 20 - 200 Gy. The percent of seedling damage and frequency of germination were determined. Callus samples were produced in vitro and exposed to gamma rays. The irradiated callus samples were processed to extract total protein, and specifically stained for superoxide dismutase (SOD) and peroxidase isozymes. Total genomic DNA was extracted from irradiated callus samples and subjected to random amplified polymorphic DNA analysis using 23 random decamer primers.

RESULTS

Gamma irradiation resulted in retardation in seedling height and decrease in germination frequency in a dose dependent manner. Inhibition assay identified variation in response between different isoforms of SOD on radiation exposure. Changes in peroxidase activity were also observed following irradiation. RAPD analysis showed that new bands appeared in the 20 Gy irradiated sample which in the case of some primers showed similarity with the control. The calli irradiated with 50 Gy and 100 Gy of gamma rays was found to have striking resemblance in banding pattern. Callus irradiated at 200 Gy showed maximum damage. DNA damage as revealed by RAPD analysis was reflected in the appearance of new bands with varying molecular weights.

CONCLUSION

New isoforms of SOD appeared after irradiation followed by 24 h recovery. Some isoforms of peroxidase reappeared in calli after 24 h recovery. Results of RAPD analysis indicated that the DNA polymorphism was dose dependent.

FluoMEP: a new genotyping method combining the advantages of randomly amplified polymorphic DNA and amplified fragment length polymorphism

PCR-based identification of differences between two unknown genomes often requires complex manipulation of the templates prior to amplification and/or gel electrophoretic separation of a large number of samples with manual methods. Here, we describe a new genotyping method, called fluorescent motif enhanced polymorphism (fluoMEP). The fluoMEP method is based on random amplified polymorphic DNA (RAPD) assay, but combines the advantages of the large collection of unlabelled 10mer primers (ca. 5000) from commercial sources and the power of the automated CE devices used for the detection of amplified fragment length polymorphism (AFLP) patterns. The link between these two components is provided by a fluorescently labeled "common primer" that is used in a two-primer PCR together with an unlabeled RAPD primer. By using the same "common primer" and a series of RAPD primers, DNA templates can be screened quickly and effectively for polymorphisms. Our manuscript describes the optimization of the method and its characterization on different templates. We demonstrate by using several different approaches that the addition of the "common primer" to the PCR changes the profile of amplified fragments, allowing for screening various parts of the genome with the same set of unlabeled primers. We also present an in silico analysis of the genomic localization of fragments amplified by a RAPD primer with two different "common primers" and alone.

Identification of an anonymous RFLP DNA probe through multiple arbitrary amplicon profiling and its use for strain differentiation in a field isolate of cellulose-degrading Aspergillus niger

The genome of Aspergillus niger (MPS-002) was subjected to RAPD fingerprinting using none different random oligonucleotide primers. A 0.7 Kb PCR amplicon, generated by primer-3 could be used as a RFLP probe to differentiate A. niger (ATCC 16880) from A. niger (MPS-002). The probe revealed DNA polymorphism internal to two different EcoRI recognition sequences spaced apart at a distance of 0.4 Kb within a 4.0 Kb EcoRI fragment of the genome of both the strains. Localized genome mapping analysis further revealed that the 0.7 Kb RFLP probe was positioned at a distance of 2.7 Kb and 0.6 Kb from the two ends of a 4.0 Kb EcoRI fragment, respectively within the genome of the two strains of A. niger.

Species identification using sequences of the trnL intron and the trnL-trnF IGS of chloroplast genome among popular plants in Taiwan

Forensic botanical comparison can be hampered by the lack of appropriate DNA databases. While DNA sequence databases for many mitochondrial loci have been established for the identification of animal species, less is known regarding the genomes of plants. We report on the use of the trnL intron and the trnL-trnF intergenic spacer (IGS) in the chloroplast genome and establish a DNA sequence database for plant species identification. The DNA sequences at these two loci from commonly encountered plants, including monocots and dicots, were aligned to establish a DNA database of local plants. The database comprises 373 individual sequences representing 80 families, 206 genera and 269 species. These plant species can be grouped to species level using both sequence and length polymorphisms at these loci. To validate the database for future forensic purposes, we sequenced 20 blind samples and searched the local database and the databases of GenBank and EMBL. Fifteen of these 20 samples used in blind trial testing matched their respective species from our local DNA database but only 6 matched species registered in the GenBank and EMBL databases. The sequences of two species used in the blind trial did not match any sequence registered in any of these databases. Cluster analysis was performed to demonstrate the family and genus distribution of samples. Neighbor-joining trees of the two DNA regions from 70 samples of the local database and 10 of the species used in the blind trials were constructed and clustered to both family and genus. The bootstrap values of the trnL intron were higher than most of those of the trnL-trnF IGS. The sequence database described in this study can be used to identify plant species using DNA sequences of the trnL intron and trnL-trnF IGS of chloroplast genome and illustrates its value in plant species identification.

Molecular variation and fingerprinting of Leucadendron cultivars (Proteaceae) by ISSR markers

BACKGROUND AND AIMS

There are more than 80 species of Leucadendron and most are used as cut flowers. Currently, more than 100 cultivars are used by industry and many of them are interspecific hybrids. The origin of most cultivars is unclear and their genetic diversity and relationships have not been studied. This investigation was carried out to evaluate the genetic variation and relationships among 30 Leucadendron cultivars.

METHODS

ISSR markers were applied to determine the genetic variation and to discriminate Leucadendron cultivars. Sixty-four ISSR primers were screened and 25 primers were selected for their ability to produce clear and reproducible patterns of multiple bands.

KEY RESULTS

A total of 584 bands of 305-2400 bp were amplified, of which 97 % were polymorphic. A dendrogram generated using the Unweighted Pair Group Method with Arithmetic Average based on a distance measure of total character difference showed that the Leucadendron cultivars clustered into two main groups. Twenty-four of the 30 cultivars can be unequivocally differentiated, but identical profiles were observed for three cultivar pairs, 'Katie's Blush' and 'Silvan Red', 'Highlights' and 'Maui Sunset', and 'Yellow Crest' and 'Yellow Devil'.

CONCLUSIONS

ISSR profiling is a powerful method for the identification and molecular classification of Leucadendron cultivars. A fingerprinting key was generated based on the banding patterns produced using two ISSR primers (UBC856 and UBC857). In addition cultivar-specific ISSR bands were obtained for 17 of the 30 Leucadendron cultivars tested.

Evaluation of molecular techniques for the genetic characterization of Saccharomyces cerevisiae strains

The applicability of different PCR-based techniques, random amplified polymorphic DNA, cleaved amplified polymorphic sequence and SSRs (simple sequence repeats) to genetically identify, typify and discriminate among Saccharomyces cerevisiae strains, was investigated. The analysis and comparison of the genetic profiles obtained for each of the techniques allowed determination of the degree of polymorphism, genetic diversity and relationships among the strains. Consequently, the discriminatory power and usefulness of the molecular techniques assayed was established. SSR analysis was the most effective method due to its high level of polymorphism, the ease of interpretation of the genetic profiles obtained, and the speed of use.

Differentiation between natural and cultivated populations of Medicago sativa (Leguminosae) from Spain: analysis with random amplified polymorphic DNA (RAPD) markers and comparison to allozymes

The conservation of a crop's wild relatives as genetic resources requires an understanding of the way genetic diversity is maintained in their populations, notably the effect of crop-to-wild gene flow. In this study, the amount of differentiation between natural and cultivated populations of Medicago sativa was analysed using random amplified polymorphic DNA (RAPD) markers and an extension of the AMOVA procedure adapted to autotetraploid organisms. Simulations of structured populations were performed to test whether AMOVA provides estimates of population structure in autotetraploids that can be directly compared to those obtained for allozyme data. Simulations showed that straight phi-statistics allow a good estimation of population differentiation when unbiased allelic frequencies are used to correct the conditional expectations of squared genetic distances. But such unbiased estimates can not be practically guaranteed, and population structure is notably overestimated when some populations are fixed for the presence of amplified fragments. However, removing fixed loci from the data set improves the statistical power of the test for population structure. The genetic variation of 15 natural and six cultivated populations of M. sativa was analysed at 25 RAPD loci and compared to estimates computed with allozymes on the same set of populations. Although RAPD markers revealed less within-population genetic diversity than allozymes, the quantitative and qualitative patterns of population structure were in full agreement with allozymes. This confirmed the conclusions drawn from the allozymic survey: crop-to-wild gene flow occurred in many locations, but some other mechanisms opposed cultivated traits to be maintained into natural populations.

High genome-wide mutation rates in vegetatively propagated bermudagrass

A cascade DNA amplification strategy that generates arbitrary signatures from amplification profiles (ASAP) was used to measure genome-wide mutation rates in bermudagrass (Cynodon). ASAP quantified nucleotide changes that were induced by irradiation, genetic instabilities and normal vegetative growth of cultivars and accessions of sterile interspecific hybrids. DNA sequence divergence between cultivar 'Tifway' and its gamma radiation-induced mutant 'Tifway II' (0.70 +/- 0.66%) was comparable to estimates in radiation-induced mutants and spontaneous sports of chrysanthemum (Chrysanthemum morifolium Ramat.). A similar divergence in sequence (0.95 +/- 0.20%) was observed in the pairwise comparison of 17 nondisjunctive 'Tifgreen' and 'Tifdwarf' accessions. Mutation during normal Tifdwarf vegetative growth was evaluated by planting sprigs and sampling their offspring. Somatic sequence divergence levels (0.004 +/- 0.007%) resulted in a mutation rate of 1.05 x 10-8 per nucleotide per generation, assuming that a bermudagrass sprig constitutes a generation of growth. These rates were comparable to those found in germinal cells and individuals of either human or Drosophila melanogaster, supporting the notion that eukaryotic evolution is generation rather than time dependent. The high accumulation of somatic mutations (10 per triploid genome) is consistent with a model whereby mutation load in a population exhibiting obligate vegetative reproduction is substantially higher than in a population under sexual or asexual reproduction. These constraints could be the cause of reported genetic instabilities in the Tifgreen-Tifdwarf complex. Finally, a long-term rate measured across accessions and indicative of the accumulation of mutations in 17 Tifgreen-Tifdwarf populations (µ = 1.02 x 10-8 per nucleotide per generation) was strikingly congruent with the bermudagrass vegetative mutation rate, suggesting absence of evolutionary constraints in the sampled genomic regions. Mutation rates calculated from across-accesions divergence estimates (5.18 +/- 0.53%) indicated that plant material was evolving 100 times faster (3.8 x 10-7 changes per nucleotide per year) than a molecular clock rate estimate for grasses, probably resulting from the compound effect of clonal growth and life span of the hybrid plant material.

Molecular nature of RAPD markers from Haemophilus influenzae Rd genome

Despite the widespread application of the random amplified polymorphic DNA (RAPD) technique, there is no experimental evidence of the molecular mechanism of random amplification starting from a complex template. To investigate this mechanism, we cloned and sequenced 23 selected RAPD bands amplified from Haemophilus influenzae Rd genomic DNA using eight decamer primers different in GC content and/or nucleotide sequence. As the whole genome sequence of H. influenzae Rd has been reported, the exact nucleotide sequence of each primer-template annealing site was identified. Results showed that, on an average, a homology of eight base pairs was involved in priming events and that the number of nonhomologous base pairings declined exponentially from the 5' end of the primer to its 3' end. The interaction between the primer and the template DNA was stabilized by the formation of secondary structures, and a perfect match of the 3' terminal region of the primer was not necessary for successful amplification. The complexity of the annealing process suggested that, in the studied reaction conditions, many primer-template annealing sites were extended in the first cycles and that differences in the efficiency of priming and replication processes led to amplification of RAPD fragments. Moreover, the distribution of the amplified regions on the H. influenzae chromosome was analyzed.

Phenotypic and genotypic comparison of symbiotic and free-living cyanobacteria from a single field site

PCR amplification techniques were used to compare cyanobacterial symbionts from a cyanobacterium-bryophyte symbiosis and free-living cyanobacteria from the same field site. Thirty-one symbiotic cyanobacteria were isolated from the hornwort Phaeoceros sp. at several closely spaced locations, and 40 free-living cyanobacteria were isolated from the immediate vicinity of the same plants. One of the symbiotic isolates was a species of Calothrix, a genus not previously known to form bryophyte symbioses, and the remainder were Nostoc spp. Of the free-living strains, two were Calothrix spp., three were Chlorogloeopsis spp. and the rest were Nostoc spp. All of the symbiotic and all but one of the free-living strains were able to reconstitute the symbiosis with axenic cultures of both Phaeoceros and the liverwort Blasia sp. Axenic cyanobacterial strains were compared by DNA amplification using PCR with either short arbitrary primers or primers specific for the regions flanking the 16S-23S rRNA internal transcribed spacer. With one exception, the two techniques produced complementary results and confirmed for the first time that a diversity of symbiotic cyanobacteria infect Phaeoceros in the field. Symbionts from adjacent colonies were different as often as they were the same, showing that the same thallus could be infected with many different cyanobacterial strains. Strains found to be identical by the techniques employed here were often found as symbionts in different thalli at the same locale but were never found free-living. Only one of the free-living strains, and none of the symbiotic strains, was found at more than one sample site, implying a highly localized distribution of strains.

Nucleic acid scanning-by-hybridization of enterohemorrhagic Escherichia coli isolates using oligodeoxynucleotide arrays

Nucleic acid scanning by hybridization (NASBH) is a non-electrophoretic typing strategy that uses gridded oligonucleotides to reproducibly characterize arbitrarily amplified nucleic acid sequences. Membrane-bound arrays of terminally-degenerate oligonucleotides were hybridized to DNA amplification fingerprinting (DAF) products from enterohemorrhagic Escherichia coli O157:H7 isolates. Numerical and cluster analysis of 64 isolates, selected by DAF to represent a single dominant amplification type identified 14 hybridization types. Results show that NASBH is a powerful alternative for the identification of closely related bacteria, can be used successfully in epidemiological studies, and holds potential in general nucleic acid diagnostics.

Scanning of nucleic acids by in vitro amplification: new developments and applications

Nucleic acids can be characterized using a variety of "fingerprinting" techniques usually based on nucleic acid hybridization or enzymatic amplification. The scanning of nucleic acids by amplification with arbitrary oligonucleotide primers has become popular because it can generate simple-to-complex patterns from anonymous DNA or RNA templates without requiring prior knowledge of nucleic acid sequence or cloned or characterized probes. Discrete loci are amplified within genomic DNA, DNA complementary to mRNA populations (cDNA), cloned DNA fragments, and even PCR products. The potential and limitations of the various genome scanning techniques, novel improvements, and their recent use in comparative and experimental biology applications, including the analysis of plant and bacterial genomes are discussed.

DNA sequences of RAPD fragments in artiodactyls

A bovine RAPD profile, generated by a 10-mer primer, was analysed by sequencing the major fragments. Three of four different fragments showed homologies to previously characterized mammalian sequences. One was 61-66% identical to LINE sequences and another was 78.5% identical to a human chromosome 2 sequence tagged site. The third fragment was 93.1% identical to the human type 2 inositol 1,4,5-trisphosphate receptor gene. This fragment had counterparts in white-tailed deer and reindeer; fragments of slightly different size in these species showed high sequence similarity and the size differences were due to varying numbers of dinucleotide microsatellite repeats inside the fragment.

Comparison of Cannabis sativa by random amplification of polymorphic DNA (RAPD) and HPLC of cannabinoids: a preliminary study

Methods are described for the HPLC and genetic analysis of herbal Cannabis sativa. The latter method was applied to 17 plants grown simultaneously, at the same site. Sixteen of these samples were also compared using HPLC, which resulted in differentiation of the plants into 3 groups. Within two of these groups, the members could not be distinguished. By RAPD analysis, using certain combinations of primers and cladistic analysis, differentiation was possible between all but two of the plants. The use of the RAPD technique enables differentiation between samples that cannot be differentiated by HPLC analysis alone.

DNA amplification fingerprinting analysis of bermudagrass (Cynodon): genetic relationships between species and interspecific crosses

We have used DNA amplification fingerprinting (DAF) to study the genetic variation of bermudagrass (Cynodon) species and cultivars of interspecific crosses that exhibit leaf-blade textural characteristics ranging from coarse to fine. Arbitrary octamer primers produced complex and reproducible amplification profiles with high levels of polymorphic DNA. Phylogenetic analysis using parsimony (PAUP) and unweighted pair group cluster analysis using arithmetic means (UPGMA) grouped 13 bermudagrass cultivars into several clusters, including one containing the African-type bermudagrasses (C. transvaalensis) and another containing the common-type bermudagrasses (C. dactylon). The latter group included C. magennissii ('Sunturf') and a interspecific C. transvaalensisxC. dactylon cross ('Midiron'), 2 cultivars that exhibited leaf textural characteristics closer to the common-types. All other C. transvaalensisxC. dactylon crosses grouped between the African and common types. An extended screen of 81 octamer primers was needed to separate cultivar 'Tifway' from the irradiation-induced mutant 'Tifway II'. The use of either template endonuclease digestion prior to amplification or arbitrary mini-hairpin primers increased detection of polymorphic DNA and simplified the task of distinguishing these closely related cultivars. Alternatively, the use of capillary electrophoresis (CE) resolved fingerprints adequately and detected products with high sensitivity, thereby promising to increase throughput and the detection of polymorphic DNA. When used to fingerprint samples from commercial sources, DAF identified bermudagrass plant material on the basis of unique reference profiles generated with selected primers. DAF represents an excellent technique for bermudagrass cultivar verification, seed certification, varietal protection, and for the identification of mistakes in plantings, mislabeled plant materials, and contamination or substitutions of sod fields.

DNA amplification fingerprinting using arbitrary mini-hairpin oligonucleotide primers

The enzymatic amplification of DNA directed by very short oligonucleotides of arbitrary sequence produces complex DNA profiles useful for genome analysis and identity testing. Mini-hairpins harboring a "core" arbitrary sequence at the 3' terminus primed the amplification of a wide range of templates ranging from plasmid DNA to plant and animal genomes. Primer core regions of only 3 nucleotides produced complex fingerprints, but the hairpin sequence also influenced the amplification reaction. Oligonucleotide substitution with degenerate bases tailored the complexity of fingerprint patterns. Simulation studies of the amplification of plasmids pUC18 and pBR322 using primers with short arbitrary cores allowed assignment of amplification products to expected regions and revealed physical interaction between annealing sites during amplification of first-round products. Mini-hairpin primers can increase detection of polymorphic DNA, and be used to study subgenomic fragments like yeast artificial chromosomes (YACs), cloned DNA and PCR products.