Comparative cytogenetics of three economically important Piper L. species from the Brazilian Amazon.

The species Piper hispidinervum, Piper aduncum, and Piper affinis hispidinervum have essential oils with high levels of safrole, dillapiole, and sarisan, respectively. Safrole is important for pharmaceutical and chemical industries, while dillapiole and sarisan are promising compounds to control insects and fungi. These species are very similar morphologically and their taxonomy is controversial.

Direct evidence for crossover and chromatid interference in meiosis of two plant hybrids (Lolium multiflorum×Festuca pratensis and Allium cepa×A. roylei).

Crossing over, in addition to its strictly genetic role, also performs a critical mechanical function, by bonding homologues in meiosis. Hence, it is responsible for an orderly reduction of the chromosome number. As such, it is strictly controlled in frequency and distribution.

GISH-based comparative genomic analysis in Urochloa P. Beauv.

The genus Urochloa P. Beauv. [syn.

Identification of ribosomal sites and karyotype analysis in Festuca ulochaeta Steud. and Festuca fimbriata Ness., grasses native to Brazil.

Festuca L. has more than 600 perennial species described, which makes it the largest genus within the family Poaceae. In Brazil, only two native species of Festuca have been described, for which cytogenetic studies need to be strengthened: Festuca ulochaeta and Festuca fimbriata.

Comparative meiosis and cytogenomic analysis in euploid and aneuploid hybrids of Urochloa P. Beauv.

The genus Urochloa includes most of the important grasses and hybrids currently used as pastures in the tropical regions. Cytogenetic analyzes have identified some aneuploid hybrids that provide new perspectives for genetic breeding. The objective was to analyze the meiotic behavior in euploid (2n = 4x = 36) and aneuploid (2n = 4x = 36 + 2) hybrids of U.

Comparative karyotype analysis among cytotypes of Cynodon dactylon (L.) Pers. (Poaceae).

Cynodon dactylon is characterized by taxonomic and systematic complexity, and polyploidy is one of the factors responsible for its genetic and morphological diversity. The aim of the present study was to compare karyotypes of C. dactylon cytotypes based on fluorescent banding and nuclear DNA content.

Characterization of aneuploidy in interspecific hybrid between Urochloa ruziziensis (R. Germ. & Evrard) Crins and Urochloa decumbens (Stapf) R. D. Webster.

The aim of the study was to characterize the type of aneuploidy present in the hybrid Urochloa ruziziensis × Urochloa decumbens and to confirm the origin of the additional chromosomes through comparative analysis of the hybrid and parental karyotypes. C and CMA banding techniques were used for chromosome differentiation. The parental genotypes showed 36 chromosomes.

Relationship between epigenetic marks and the behavior of 45S rDNA sites in chromosomes and interphase nuclei of Lolium-Festuca complex.

The grasses of the Lolium-Festuca complex show a prominent role in world agricultural scenario. Several studies have demonstrated that the plasticity of 45S rDNA sites has been recently associated with the possible fragility of the loci. Often, these fragile sites were observed as extended sites and gaps in metaphases.

45S rDNA sites in meiosis of Lolium multiflorum Lam.: variability, non-homologous associations and lack of fragility.

In this study, we evaluated the behavior of 45S ribosomal DNA (rDNA) sites during the meiosis of Lolium multiflorum. The reason to study it in this species is that 45S rDNA sites are usually visualized as gaps in mitotic metaphase chromosomes and were initially denominated fragile sites (FSs). In different species, FSs were related to rearrangements that alter the karyotype and affect the chromosome pairing in meiosis.

Location of low copy genes in chromosomes of Brachiaria spp.

Repetitive DNA sequences have been widely used in cytogenetic analyses. The use of gene sequences with a low-copy-number, however, is little explored especially in plants. To date, the karyotype details in Brachiaria spp.

Fragile sites of 45S rDNA of Lolium multiflorum are not hotspots for chromosomal breakages induced by X-ray.

Sites of 45S rDNA of Lolium are regions denominated fragile sites (FSs), constituting regions slightly stained with DAPI due to increased DNA unpacking in metaphasic chromosomes. Considered to be fragile regions in the genome, the FSs might be more responsive to induced breaks and result in chromosomal fragments and rearrangements, unless repairing mechanisms such as recombination or de novo telomere formation play a role at the break site of the DNA. Thus, this study aimed at investigating if SFs from Lolium are hotspots for the occurrence of breakages induced by X-ray and if they are regions favorable to synthesize new telomeres, using Hordeum vulgare as a comparative model.

Chromosomal distribution of H3K4me2, H3K9me2 and 5-methylcytosine: variations associated with polyploidy and hybridization in Brachiaria (Poaceae).

Assessment of chromosomal distribution of modified histones and 5-methylcytosine shown that there are diversification of chromosomal types among species of Brachiaria and its interspecific hybrids. Histone post-translational modifications and DNA methylation are epigenetic processes that are involved in structural and functional organization of the genome. This study compared the chromosomal distribution of modified histones and 5-methylcytosine (5-mCyt) in species and interspecific hybrids of Brachiaria with different ploidy levels and reproduction modes.

Decondensation of chromosomal 45S rDNA sites in Lolium and Festuca genotypes does not result in karyotype instability.

Fragile sites (FSs) in plants have been described for species like Lolium and other grasses. Whereas in humans FSs were shown to be involved in genome instabilities; the consequences of FSs expression in plants are not known yet. To evaluate whether FSs cause karyotype instabilities, we assessed the frequency of micronuclei and lagging chromosomes in meristematic cells, the stability of the DNA content, and the occurrence of neocentromeres in the presumed chromosomal fragments of Lolium perenne, Lolium multiflorum, Festuca arrundinacea, and two Festulolium hybrids.

Ribosomal DNA in diploid and polyploid Setaria (Poaceae) species: number and distribution.

Setaria Beauvois, 1812 is a genus of economically important forage species, including Setaria italica (Linnaeus, 1753) Beauvois, 1812 and Setaria viridis (Linnaeus, 1753) Beauvois, 1812, closely related species and considered as model systems for studies of C4 plants. However, complications and uncertainties related to taxonomy of other species of the genus are frequent due to the existence of numerous synonyms for the same species or multiple species with the same name, and overlapping of morphological characteristics. Cytogenetic studies in Setaria can be useful for taxonomic and evolutionary studies as well as for applications in breeding.

Effect of SPL (Spent Pot Liner) and its main components on root growth, mitotic activity and phosphorylation of Histone H3 in Lactuca sativa L.

Spent Pot Liner (SPL) is a solid waste from the aluminum industry frequently disposed of in industrial landfills; it can be leached and contaminate the soil, sources of drinking water and plantations, and thus may pose a risk to human health and to ecosystems. Its composition is high variable, including cyanide, fluoride and aluminum salts, which are highly toxic and environmental pollutants. This study evaluated the effect of SPL and its main components on root growth and the mitosis of Lactuca sativa, by investigating the mechanisms of cellular and chromosomal alterations with the aid of immunolocalization.

Chromosomal distribution and evolution of abundant retrotransposons in plants: gypsy elements in diploid and polyploid Brachiaria forage grasses.

Like other eukaryotes, the nuclear genome of plants consists of DNA with a small proportion of low-copy DNA (genes and regulatory sequences) and very abundant DNA sequence motifs that are repeated thousands up to millions of times in the genomes including transposable elements (TEs) and satellite DNA. Retrotransposons, one class of TEs, are sequences that amplify via an RNA intermediate and reinsert into the genome, are often the major fraction of a genome. Here, we put research on retrotransposons into the larger context of plant repetitive DNA and genome behaviour, showing features of genome evolution in a grass genus, Brachiaria, in relation to other plant species.

Bioaccumulation and effects of lanthanum on growth and mitotic index in soybean plants.

Rare earth elements such as lanthanum (La) have been used as agricultural inputs in some countries in order to enhance yield and improve crop quality. However, little is known about the effect of La on the growth and structure of soybean, which is an important food and feed crop worldwide. In this study, bioaccumulation of La and its effects on the growth and mitotic index of soybean was evaluated.

Immunolocalization of chromosome-associated proteins in plants - principles and applications.

The use of the immunolocalization technique combined with cytogenetic and epigenetic studies is an indispensable tool and has contributed significantly to the analysis of the structure and function of chromosomes, since it can provide information about the spatial or temporal distribution of a given protein in the nucleus and chromosomes. Several chromosome-associated proteins in plant cells have already been identified by immunolocalization, such as histone and non-histone proteins and cell division-related protein (mitosis and meiosis). The principle of the immunolocalization technique in plants basically involves fixation and permeabilization of cells, the use of monoclonal or polyclonal antibodies attached to a signaling molecule, usually a fluorochrome and detection of the target molecule by using an epifluorescence microscope.

Functional repetitive sequences and fragile sites in chromosomes of Lolium perenne L.

Lolium perenne is considered a high-quality forage widely used in temperate regions to meet the shortage of forage during the winter. In this species, some peculiarities related to cytogenetic aspects have already been described, as the variability in number and position of 45S ribosomal DNA (rDNA) sites and the expression of fragile sites, which require further studies to support the understanding of their causes and consequences. In this way, this study aimed to evaluate the relationship between the expression of fragile sites and functional repetitive sequences (rDNA and telomeric) in chromosomes of diploid and polyploid cultivars of L.

Genotoxicity in Astyanax bimaculatus (Twospot Astyanax) exposed to the waters of Engano River (Brazil) as determined by micronucleus tests in erythrocytes.

Changes in aquatic environments are potentially large, and effects on biota are highly variable. In Santa Catarina State, Brazil, the main sources of pollution in headwaters are wastewater, pesticides, and animal waste, which contain chemical and organic additives, and there is little knowledge about their effects on aquatic organisms. This study was aimed at investigating the possible genotoxic effects of the waters of the Engano River through the micronucleus (MN) test in Astyanax bimaculatus erythrocytes.