SEARCH · PubMed Health

Results for “GC content”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources

PubMed1978

[The GC content of a group of H2S- enterobacterial related to the genus Citrobacter].

The deoxyribonculeic acid (DNA) of 106 strains of Enterobacteria was analysed for the guanine + cytosine (GC) content. These strains, whose origin and principal characters are described in the text, belong to the genera Citrobacter (C. freundii H2S-) and Levinea (L. malonatica and L. amalonatica). Four other groups or classes named C.D.E. and F. could not be classified on the base of the usual phenotypic criteria. DNA from the strains of Levinea has a GC% of 50.3 to 53.3, while DNA from the strains of C. freundii H2S- has a GC% of 48.6 to 51.7. The representative values from the new classes are C, 50.9%; D, 54%; E, 52.7%; F, 49.5%. For the latter a genomic heterogeneity was shown, expressing itself as two subpopulations whose average GC% are 51.7 and 48.6 respectively. Statistical analysis of the averages give a significant individuality to these new classes.

Citrobacter↗

PubMedDate not supplied

[Character of the methylation and reassociation of wheat DNA fractions differing in their nucleotide composition].

The GC and AT fractions (GC content is 55.2 and 36.2 mole %, respectively) were isolated from wheat germ DNA by the thermal fractionation method (sequential thermal DNA denaturation followed by separation of denatured and undenatured DNA molecules by hydroxyapatitie chromatography). The amount of each of the two fractions isolated corresponds to about 25% of the total DNA. The 5-methylcytosine (m5C) content in the GC fraction (9.2 mole %) is 4.6 times higher than in the AT fraction. The DNA fractions isolated are very different in the level of methylation of cytosine residues (m5C/C+m5C ratio differs 3 times), in the amount of respective pyrimidine isostichs and in the renaturation kinetics. In contrast to the AT fraction, in the GC fraction the amount of dipyrimidine isostichs is higher than monopyrimidine ones. The AT and GC fractions isolated contain unique, moderately and highly reiterated nucleotide sequences. About 90% of the GC fraction is represented by reiterated sequences. The isolated (from the GC fraction) highly reiterated sequences (GC fraction I, Cot = 2.8 X 10(-2)) are very similar to the original GC fraction in the GC and m5C contents as well as in the amount of m5C in the respective pyrimidine isostichs. GC fraction I differs from the total GC fraction in a lower pyrimidine clustering degree. In total DNA and in GC and AT fractions m5C is found in mono- (34-40% of total m5C), di-(26-30%) and in all longer pyrimidine isostichs. It is suggested that in plants there exist many types of DNA sequences to be methylated as well as many respective DNA methylases.

Base Sequence↗

PubMed2025

Negative dataset selection impacts machine learning-based predictors for multiple bacterial species promoters.

MOTIVATION: Advances in bacterial promoter predictors based on machine learning have greatly improved identification metrics. However, existing models overlooked the impact of negative datasets, previously identified in GC-content discrepancies between positive and negative datasets in single-species models. This study aims to investigate whether multiple-species models for promoter classification are inherently biased due to the selection criteria of negative datasets. We further explore whether the generation of synthetic random sequences (SRS) that mimic GC-content distribution of promoters can partly reduce this bias. RESULTS: Multiple-species predictors exhibited GC-content bias when using CDS as a negative dataset, suggested by specificity and sensibility metrics in a species-specific manner, and investigated by dimensionality reduction. We demonstrated a reduction in this bias by using the SRS dataset, with less detection of background noise in real genomic data. In both scenarios DNABERT showed the best metrics. These findings suggest that GC-balanced datasets can enhance the generalizability of promoter predictors across Bacteria. AVAILABILITY AND IMPLEMENTATION: The source code of the experiments is freely available at https://github.com/maigonzalezh/MultispeciesPromoterClassifier.

Machine Learning↗

PubMed2026

Genome-based predictions of metabolic preferences and substrate phenotypes in psychrotrophic bacteria from permafrost environments.

Genomes reveal vast functional potential, but harbor genomic noise that obscures prediction of metabolic and environmental preferences. Genomic databases are skewed towards clinically relevant and easily cultivated bacteria, limiting predictions for diverse and underrepresented environmental taxa. Psychrotrophic bacteria, which can survive and grow in cold, nutrient-limited, dry, and saline environments, are especially underrepresented despite their relevance for understanding microbial responses to changing cold environments and potential biotechnological value given growth at low temperatures. Assembling complete genomes of 48 isolates from Alaskan permafrost, seasonally frozen active layer soils, and terrestrial ice, we used Kyoto Encyclopedia of Genes and Genomes (KEGG) ortholog annotations to evaluate the predictability of metabolic resource-use traits observed using phenotypic tests. Genome-predicted values for glycolytic versus gluconeogenic catabolic preference index, or sugar-acid preference (SAP), explained over 50% of the variance in empirically observed SAP. SAP was inversely correlated to genomic GC content, which follows phylum-level trends, indicating that coarse metabolic preference covaries with phylogeny. Regularized elastic net models offered a more granular view, linking KEGG genes to specific substrate utilization and sensitivity phenotypes and yielding moderate but reproducible accuracy (AUC 0.70-0.79) for 11 substrates, demonstrating that specific substrate responses may be predictable from relatively small subsets of KO genes. These results extend recent advances, such as the SAP metric, and highlight associations among genomic GC content, phylum, and broad metabolic strategy. Linking genomic content to phenotype using isolates is a necessary step toward predictive models of microbial function in environmental communities, and this work can be used for hypothesis generation, with applications towards more expansive data sets.IMPORTANCECold region soils and ice host psychrotrophic bacteria with metabolic traits and adaptations that enable persistence in harsh, resource-limited environments. However, these taxa are underrepresented in genomic reference databases dominated by well-studied, mesophilic organisms. This gap limits inference of ecological strategies and our ability to predict how these microbes may influence the large, thaw-vulnerable carbon reservoirs in permafrost. Here, we show that genomic GC content is associated with the sugar-versus-acid catabolic preference (SAP) of isolates across major phyla, suggesting that broad genomic features may provide a coarse signal of metabolic strategy. We demonstrate that a modified SAP metric, using binary (positive/negative) substrate utilization rather than detailed growth rate measurements, is moderately predictive, thus extending its application to slow-growing or difficult-to-culture taxa. Together, these advances broaden the toolkit for linking genome content to resource-use traits (phenotype) in poorly characterized, cold-adapted bacteria and offer a tractable entry point to broad prediction and hypothesis generation.

Genome, Bacterial↗

PubMed1977

Deoxyribonucleic acid base composition of Simonsiellaceae.

The molar percentages of guanine plus cytosine in the DNA of 51 strains of Simonsiellaceae were determined by buoyant density ultracentrifugation of cell lysates in CsCl. The DNA base ratios ranged from 41-55 mole-% guanine plus cytosine. These values fall within the range known for the Order Cytophagales, the non-fruiting gliding bacteria, and are outside the range of the Order Myxobacterales, the fruiting myxobacteria. Among the strains of the genus Simonsiella, four distinct group can be delineated on the basis of source of origin (sheep, dog, cat, human) and GC content. The neotype of Alysiella filiformis has a GC content of 45.4 mole-%.

Animals↗

PubMed2026

Divergent trajectories of genome architecture and chromosome evolution in ferns and angiosperms.

Ferns and angiosperms represent the two largest vascular plant lineages but exhibit striking genomic and ecological contrasts. We investigated whether differences in genome size, chromosome architecture, GC content, and stomatal traits reveal divergent evolutionary trajectories between these lineages. We assembled the most comprehensive dataset to date, integrating genome size, chromosome number and size, GC content, and stomatal traits for over 1100 fern species and compared it with an extensive angiosperm dataset. Ferns exhibited markedly lower variability and c. 16-fold slower rates of chromosome size evolution than angiosperms. A persistent positive relationship between genome size and chromosome number in ferns suggests limited cytological post-polyploid diploidization. While ferns generally possess larger stomata, this difference disappears after accounting for genome size, indicating that nucleotypic constraints, rather than lineage-specific physiology, dictate stomatal dimensions. Both groups share a unimodal GC-genome size relationship peaking at c. 14 Gbp. Larger fern chromosomes imply lower genome-wide recombination rates, potentially limiting genetic reshuffling and adaptive potential. Our results highlight fundamentally divergent evolutionary trajectories, likely shaped by meiotic symmetry in ferns and meiotic asymmetry, possibly centromere drive, and post-polyploid diploidization in angiosperms, defining the functional and genomic landscapes of these lineages across deep evolutionary timescales.

Genome, Plant↗

PubMed2025

Characterization of non-crossover recombination spectrum by single-microspore sequencing in maize and rice.

Meiotic DNA double-strand breaks (DSB) are crucial for chromosome recombination. The repair of DSB gives two outcomes: crossover (CO) and non-crossover (NCO). CO involves the bidirectional exchange between homologous chromosomes, whereas NCO refers to the unidirectional transfer of chromosome fragments. NCO can be categorized into NCO with gene conversion and NCO without gene conversion. Due to technological constraints, previous studies have focused more on CO than on NCO. In this study, we isolated single microspores from meiotic tetrads of maize (Zea mays) and rice (Oryza sativa) and conducted deep single-microspore genome sequencing to characterize NCO gene conversion (NCO-GC). Under highly stringent conditions, 101 CO and 902 NCO-GC tracts were identified in four maize tetrads, while 173 CO and 279 NCO-GC tracts were identified in six rice tetrads. In both maize and rice, NCO-GC was more prone to occur in the upstream and downstream of genes, as well as the introns. It also had a significant distribution in transposon regions. A common A-rich motif was enriched in the NCO-GC tracts of maize and rice. GC-biased gene conversion (gBGC) likely contributed to the bimodality of the GC content at the third codon position (GC3), and we discovered a significant proportional relationship between the number of DSBs and the GC content. These findings provide evidence that NCO-GC exhibits a distinct pattern compared with CO and may play an important role in gene and genome evolution.

Oryza↗

PubMed1977

The structure of animal mitochondrial DNA (base composition, pyrimidine clusters, character of methylation).

Base composition, content of pyrimidine isopliths and the degree of methylation of mitochondrial DNA (mtDNA) and nuclear DNA (nDNA) from various vertebrates and protozoon Crithidia oncopelti have been studied. MtDNAs from mammals (ox, rat) do not differ in fact in the GC content from the respective nDNA. The GC content in mtDNA from fishes (sheat fish) and birds (duck, chicken) is 1.5-2.5 mole % higher than in the respective nDNA. Kinetoplast DNA (kDNA) from Crithidia oncopelti (GC = 42.9 mole %) differs significantly in base composition from nDNA (GC = 51.3 mole %). All the mtDNA and kDNA studied differ from the respective nDNA by a lower degree of pyrimidine clustering. The amount of mono and dipyrimidine fragments in mtDNA is more than 30 mole %, whereas in nDNA it does not exceed 23 mole %. The quantity of long pyrimidine clusters (hexa and others) is 2-4 times lower in mtDNA than in nDNA. The lower degree of clustering of pyrimidine nucleotides seems to be a specific feature of all the mtDNA studied. This may be indicative of common traits in the organization and origin of mtDNA. All mtDNA of vertebrates contain 5-methylcytosine as a 'minor' base (1.5- 3.15 mole %) and surpass by 1.5-2 times the respective nDNA in the methylation degree. It has been found that in animals mtDNA is species specific as far as the 5-methyl-cytosine content is concerned. In mitochondria and nuclei of rat liver certain DNA methylase activity has been detected, which provides in vitro the methylation of cytosine residues both in homologous DNA and various heterologous DNAs. The specificity of methylation in vitro of cytosine residues in the same heterologous DNA from E. coli B varies with the source of enzymes. The mitochondrial enzyme methylates cytosine as the lone monopyrimidine residue, whereas the nuclear enzyme methylase cytosine in the di- and tripyrimidine fragments.

Animals↗

PubMed2026

Global microbial DNA signatures of temperature and nutrient limitation across ecosystems.

Microbial genomes continuously adapt to environmental conditions, but identifying universal signatures of adaptation remains challenging. Here we show that environmental temperature can be accurately predicted across ecosystems from DNA composition alone (R2 = 0.75), using tetranucleotide frequencies from 1,235 marine and soil metagenomes and a machine learning approach. This predictive signal was also apparent within individual taxa, consistent with a fundamental temperature-associated signature. By contrast, GC content exhibited opposite correlations with temperature in soil (positive) and marine (negative) environments. This phenomenon was probably driven by differences in nutrient availability, as GC content increases with nutrients while nutrients decrease with temperature in marine samples. By integrating these observations, we identified specific tetranucleotides, with 50% GC, that displayed consistent and robust temperature correlations across environments and may have contributed to the stability of predictions. This work highlights metagenome-wide DNA-temperature associations, relevant for understanding microbial community responses to global changes.

Journal Article↗

PubMed2025

Codon Composition in Human Oocytes Reveals Age-Associated Defects in mRNA Decay.

Oocytes from women of advanced reproductive age exhibit diminished developmental potential, but the underlying mechanisms remain incompletely defined. Oocyte maturation depends on translational control of maternal mRNA synthesized during growth. We performed a computational analysis on human oocytes from women <30 versus ≥40 years and observed that mRNA GC content correlates negatively with half-life in oocytes from young (<30 yr) but positively with oocytes from aged (>40 yr) women. In young oocytes, longer mRNA half-life is associated with lower protein abundance, whereas in aged oocytes GC content correlates positively with protein abundance. During the GV-to-MII transition, codon composition stratifies stability: codons that support rapid translation (optimal) stabilize mRNA, while slow-translating codons (non-optimal) promote decay. With reproductive aging, GC-containing codons become more optimal and align with increased protein abundance. These findings indicate that reproductive aging remodels codon-optimality-linked, translation-coupled mRNA decay, stabilizing a subset of GC-rich maternal mRNA that may be prone to excess translation during maturation. Our analysis is explicitly within human reproductive aging; it does not revisit cross-species stability rules. Instead, it shows that sequence-stability relations are reprogrammed with age within human oocytes, including an inversion of the GC-stability association during GV-to-MII transition. Disruption of the normal mRNA clearance program in aged oocytes may compromise oocyte competence and alter maternal mRNA dosage, with downstream consequences for early embryonic development.

Humans↗

PubMedDate not supplied

[Changes in the methylated sequences and molecular population of wheat DNA during germination].

The fractions of unique (Cot less than 405), moderately (Cot=0.13--405) and highly reiterated (Cot less than 0--0.13) sequences were isolated from DNA of wheat seeds and 3 day old seedlings, and GC content, amount of 5-methylcytosine and its distribution among various pyrimidine isostichs in the fractions isolated were studied. Different in Cot value DNA fractions from seeds or from seedlings are similar in GC content and in all other characteristics studied. Seed DNA differs from DNA of seedlings in the content of pyrimidine isostichs from the respective fractions of reiterated sequences. Pronounced differences in the amount of pyridmidine clusters with various base composition in the corresponding fractions of DNA from seeds and seedlings were found. These differences in the frequencies of respective pyrimidine clusters from DNA of seeds and seedlings may be considered as being a result of changes in the molecular population of wheat DNA on germination. The seed and seedling DNA differ significantly in the 5-methylcytosine content in the respective pyrimidine isostichs isolated from unique sequences. In the seedling DNA some other nucleotide sequences are to be methylated as compared to DNA of dormat seeds. Thus, on germination some changes occur in DNA methylation as well as in the genome organization.

Base Sequence↗

PubMed1976

Mechanisms of chromosome banding. IX. Are variations in DNA base composition adequate to account for quinacrine, Hoechst 33258 and daunomycin banding?

Prior studies on subfractions of mouse and Kangaroo rat DNA have suggested that variations in base concentration within a given genome may not be great enough to account for Q-banding. To examine this with another species, calf DNA was subfractionated by CsCl ultracentrifugation into GC-rich satellites and the main band DNA was further fractionated into AT-rich, intermediate and GC-rich portions. The effect of varying concentrations of these DNAs on quinacrine and Hoechst 33258 fluorescence was examined. Although with both compounds there was less fluorescence in the presence of the GC-rich satellites than main band fractions, these results per se did not answer the question of whether the variation in base composition alone was adequate to account for chromosome banding. To answer this the fluorescence observed in the presence of DNA of a given base composition was related to the fluorescence observed in the presence of DNA of 40% GC content (F/F40). This allowed the derivation of a term B which indicated the relative change in fluorescence per 1% change in base composition of DNA. To determine the percent change in fluorescence observed in Q-banding, the photoelectric recordings of Caspersson et al. (1971) were used. From these data we conclude: 1. Quinacrine is twice as sensitive to changes in base composition as Hoechst 33258. 2. Variation in the base content of DNA along the base content of DNA along the chromosome is sufficient to account for most Q-banding, except possibly for some of the extremes of quinacrine fluorescence. This was further examined with daunomycin. Even though daunomycin gives good fluorescent banding, DNAs varying in base composition from 100 to 40% GC content all resulted in the same relative fluorescence of 0.03. However, in the presence of poly (dA-dT) the relative fluorescence was 0.85, indicating a great sensitivity to very AT-rich DNA. This suggests that with daunomycin and possibly other fluorochromes, stretches of very AT-rich DNA may be more important in fluorescent banding than simple variation in mean base composition.

Adenine Nucleotides↗

PubMed1979

Biophysical properties of virions of human adenovirus of the type 6 and its DNA.

A study has been made of human adenovirus type 6 (Ad 6) which belongs to the C subgroup of the nononcogenic adenoviruses. The buoyant density of the Ad 6 virions in CsCl gradient was 1.3545 +/- 0.0010 g/cm3. The DNA content determined from the buoyant density values and direct phosphorus analysis was 11.2 +/- 0.5 and 11.5 +/- 0.5 per cent, respectively. The S20,w0 and D20,w0 values for the Ad 6 virions were 795 +/- 18S and (3.255 +/- 0.035) X 10-8 cm2/s. The hydrodynamic parameters of the viral particle and its volume as well as the specific partial volume, the content and the molecular weight of the DNA have yielded a molecular weight of the virions of (203.6 +/- 10.0) X 10(6). The sedimentation constant and the intrinsic viscosity of the DNA have been found to be 32.7 +/- 0.7S and 93.5 +/- 5.0 dl/g, respectively. The molecular weight of the DNA found from these results is (23.4 +/- 0.8) X 10(6). The buoyant density of the Ad 6 DNA measured in CsCl and Cs2SO4 density gradients was 1.7128 +/- 0.0010 and 1.427 +/- 0.001 g/cm3, respectively. The GC content found from the buoyant density and the melting temperature (90.5 +/- 0.1 degrees C in 1 SSC and 75.0 +/- 0.1 degrees C in 0.1 SSC) was 52.6 +/- 1.0 per cent, that is, it is considerably lower than the GC content of 56-60 per cent which, according to the "Green's rule", should be typical of the DNAs of all the human adenoviruses of the subgroup C (30).

Adenoviruses, Human↗

PubMed2026

HiCPotts: An R/Bioconductor package to identify significant interactions in chromosome conformation capture data and model sources of bias.

MOTIVATION: Chromosome Conformation Capture methods, including Hi-C, micro-C or Capture-C, are used to map chromatin interactions genome-wide. Most of the existing computational methods do not account for sources of bias (such as DNA accessibility, GC content or TE content) in the data. RESULTS: We previously developed ZipHiC, a Bayesian method based on the hidden Markov random field (HMRF) model and the Approximate Bayesian Computation (ABC), that uses zero-inflated Poisson distribution to model the noise, signal and false signal of the data and showed that this approach was able to detect bias from DNA accessibility, GC content and TE content in both Hi-C and micro-C data. Here, we present HiCPotts, another Bayesian method based on the HMRF model and the ABC that uses a zero-inflated Negative Binomial distribution instead to model the noise and signal of the data. We systematically show that HiCPotts reduces false positives and increases recovery of true interactions compared to ZipHiC, but also compared to other methods such as FastHiC, Juicer and HiCExplorer. Most importantly, we provide an R/Bioconductor package that allows modelling the noise, signal and false signal using various distributions such as the zero-inflated Negative Binomial (ZINB) and the zero-inflated Poisson distribution (ZIP). AVAILABILITY AND IMPLEMENTATION: https://bioconductor.org/packages/HiCPotts/. SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.

Approximate Bayesian Computation↗

PubMed2026

Chromosome-level de novo assembly of the nuclear and mitochondrial genomes of Arcopilus aureus, a filamentous fungus with multifaceted ecological and economic roles.

The filamentous fungus Arcopilus aureus (Sordariale: Chaetomiaceae) is notable for its multi-domain significance across agriculture, medicine, and industry. In this study, we generated a chromosome-level nuclear genome and a complete circular mitogenome for A. aureus by integrating data from next-generation sequencing, PacBio HiFi, and Hi-C technologies. The final nuclear genome assembly spans 33.77 Mb (GC content: 57.67%), and was organized into seven chromosomal-sized scaffolds (only one gap) with an N50 size of 5.09 Mb and BUSCO completeness of 95.91%. A total of 10,282 protein-coding genes, 228 non-coding RNAs, and ~1.77 Mb of repetitive elements were predicted in the nuclear genome. By contrast, the mitogenome of A. aureus is 33,820 bp in length, with a GC content of 25.96%. It harbors 15 typical mitochondrial protein-coding genes, one unidentified ORF, two rRNAs (small subunit rns and large subunit rnl), and 28 tRNAs. This high-quality genome assembly provides a valuable resource for understanding the ecology, genetics, and evolution of A. aureus, which facilitates elucidating its mechanisms of biocontrol, infection, and metabolite synthesis.

Genome, Mitochondrial↗

PubMed2025

Tracing the evolution and genomic dynamics of mating-type loci in Cryptococcus pathogens and closely related species.

Sexual reproduction in basidiomycete fungi is governed by MAT loci (P/R and HD), which exhibit remarkable evolutionary plasticity, characterized by expansions, rearrangements, and gene losses often associated with mating system transitions. The sister genera Cryptococcus and Kwoniella provide a powerful framework for studying MAT loci evolution owing to their diverse reproductive strategies and distinct architectures, spanning bipolar and tetrapolar systems with either linked or unlinked MAT loci. Building on recent comparative genomic analyses, we generated additional chromosome-level assemblies, uncovering distinct trajectories shaping MAT loci organization. Contrasting with the small-scale expansions and gene acquisitions observed in Kwoniella, our analyses revealed independent expansions of the P/R locus in tetrapolar Cryptococcus, possibly driven by pheromone gene duplications. Notably, these expansions coincided with a pronounced GC-content reduction best explained by reduced GC-biased gene conversion following recombination suppression, rather than relaxed codon usage selection. Diverse modes of MAT locus linkage were also identified, including three previously unrecognized transitions: one resulting in a pseudobipolar arrangement and two leading to bipolarity. All three transitions involved translocations. In the pseudobipolar configuration, the P/R and HD loci remained on the same chromosome but genetically unlinked, whereas the bipolar transitions additionally featured rearrangements that fused the two loci into a nonrecombining region. Mating assays confirmed a sexual cycle in C. decagattii, demonstrating its ability to undergo mating and sporulation. Progeny analysis in K. mangrovensis revealed substantial ploidy variation and aneuploidy, likely stemming from haploid-diploid mating, yet evidence of recombination and loss of heterozygosity indicates that meiotic exchange occurs despite irregular chromosome segregation. Our findings underscore the importance of continued diversity sampling and provide further evidence for convergent evolution of fused MAT loci in basidiomycetes, offering new insights into the genetic and chromosomal changes driving reproductive transitions.

MAT genes↗

PubMed2025

The complex evolution and genomic dynamics of mating-type loci in Cryptococcus and Kwoniella.

Sexual reproduction in basidiomycete fungi is governed by MAT loci (P/R and HD), which exhibit remarkable evolutionary plasticity, characterized by expansions, rearrangements, and gene losses often associated with mating system transitions. The sister genera Cryptococcus and Kwoniella provide a powerful framework for studying MAT loci evolution owing to their diverse reproductive strategies and distinct architectures, spanning bipolar and tetrapolar systems with either linked or unlinked MAT loci. Building on recent comparative genomic analyses, we generated additional chromosome-level assemblies, uncovering distinct trajectories shaping MAT loci organization. Contrasting with the small-scale expansions and gene acquisitions observed in Kwoniella, our analyses revealed independent expansions of the P/R locus in tetrapolar Cryptococcus, possibly driven by pheromone gene duplications. Notably, these expansions coincided with a pronounced GC-content reduction best explained by reduced GC-biased gene conversion following recombination suppression, rather than relaxed codon usage selection. Diverse modes of MAT locus linkage were also identified, including three previously unrecognized transitions: one resulting in a pseudobipolar arrangement and two leading to bipolarity. All three transitions involved translocations. In the pseudobipolar configuration, the P/R and HD loci remained on the same chromosome but genetically unlinked, whereas the bipolar transitions additionally featured rearrangements that fused the two loci into a nonrecombining region. Mating assays confirmed a sexual cycle in Cryptococcus decagattii, demonstrating its ability to undergo mating and sporulation. Progeny analysis in Kwoniella mangrovensis revealed substantial ploidy variation and aneuploidy, likely stemming from haploid-diploid mating, yet evidence of recombination and loss of heterozygosity indicates that meiotic exchange occurs despite irregular chromosome segregation. Our findings underscore the importance of continued diversity sampling and provide further evidence for convergent evolution of fused MAT loci in basidiomycetes, offering new insights into the genetic and chromosomal changes driving reproductive transitions.

Genes, Mating Type, Fungal↗

PubMed1979

Deoxyribonucleic acid binding studies on several new anthracycline antitumor antibiotics. Sequence preference and structure--activity relationships of marcellomycin and its analogues as compared to adriamycin.

The deoxyribonucleic acid (DNA) binding characteristics of adriamycin and several new anthracycline glycosides, including marcellomycin, aclacinomycin, rudolfomycin, musettamycin, and pyrromycin, have been studied. The fluorescence spectra were determined for all six anthracyclines, and the fluorescence quenching effects caused by interactions with the natural DNAs poly(dAdT)--poly(dAdT) and poly(dGdC) were characterized. Binding parameters were determined by Scatchard analyses of results obtained by spectrofluorometric titrations of anthracyclines with DNA. Consistent with earlier structure--activity relationship studies of nucleic acid synthesis inhibitory effects, the results demonstrate a correlation between the length of the glycosidic side chain and DNA binding affinity. In addition, the sugar residue 2-deoxyfucose appears to confer greater DNA binding ability than do the sugars rednosamine and cinerulose when present in the terminal position of the glycosidic side chain, also in agreement with earlier studies. The sequence preference of anthracycline--DNA interaction has been examined by using DNAs of varying GC content, including the naturally occurring calf thymus DNA (43% GC), Clostridium perfringens DNA (28% GC), and Micrococcus luteus DNA (72% GC) and the synthetic double-stranded copolymers poly(dGdC)--poly(dGdC) and poly(dAdT)--POLY(DAdT). The results demonstrate that although adriamycin shows an absolute requirement for GC sequences for DNA binding, marcellomycin and its analogues showed no such sequence requirement. Furthermore, an AT preference for DNA binding was demonstrated with marcellomycin and its analogues.

Aclarubicin↗