The Cerrado (Brazil) plant cytogenetics database

Cerrado is a biodiversity hotspot that has lost ca. 50% of its original vegetation cover and hosts ca. 11,000 species belonging to 1,423 genera of phanerogams. For a fraction of those species some cytogenetic characteristics like chromosome numbers and C-value were available in databases, while other valuable information such as karyotype formula and banding patterns are missing. In order to integrate and share all cytogenetic information published for Cerrado species, including frequency of cytogenetic attributes and scientometrics aspects, Cerrado plant species were searched in bibliographic sources, including the 50 richest genera (with more than 45 taxa) and 273 genera with only one species in Cerrado. Determination of frequencies and the database website (http://cyto.shinyapps.io/cerrado) were developed in R. Studies were pooled by employed technique and decade, showing a rise in non-conventional cytogenetics since 2000. However, C-value estimation, heterochromatin staining and molecular cytogenetics are still not common for any family. For the richest and best sampled families, the following modal 2n counts were observed: Oxalidaceae 2n = 12, Lythraceae 2n = 30, Sapindaceae 2n = 24, Solanaceae 2n = 24, Cyperaceae 2n = 10, Poaceae 2n = 20, Asteraceae 2n = 18 and Fabaceae 2n = 26. Chromosome number information is available for only 16.1% of species, while there are genome size data for only 1.25%, being lower than the global percentages. In general, genome sizes were small, ranging from 2C = ca. 1.5 to ca. 3.5 pg. Intra-specific 2n number variation and higher 2n counts were mainly related to polyploidy, which relates to the prevalence of even haploid numbers above the mode of 2n in most major plant clades. Several orphan genera with almost no cytogenetic studies for Cerrado were identified. This effort represents a complete diagnosis for cytogenetic attributes of plants of Cerrado.

Spatial Separation of Parental Genomes in Preimplantation Mouse Embryos

We have used two different experimental approaches to demonstrate topological separation of parental genomes in preimplantation mouse embryos: mouse eggs fertilized with 5-bromodeoxyuridine (BrdU)-labeled sperm followed by detection of BrdU in early diploid embryos, and differential heterochromatin staining in mouse interspecific hybrid embryos. Separation of chromatin according to parental origin was preserved up to the four-cell embryo stage and then gradually disappeared. In F1 hybrid animals, genome separation was also observed in a proportion of somatic cells. Separate nuclear compartments during preimplantation development, when extreme chromatin remodelling occurs, and possibly in some differentiated cell types, may be associated with epigenetic reprogramming.

IDENTIFICATION OF CHROMOSOMES IN SECALE MONTANUM AND INDIVIDUAL S. MONTANUM CHROMOSOME ADDITIONS TO 'KHARKOV' WHEAT BY HETEROCHROMATIN BANDS AND CHROMOSOME MORPHOLOGY

Heterochromatin staining along with chromosome morphology was used to identify the chromosomes of Secale montanum Guss. in five accessions. The characteristics of all seven S. montanum chromosomes were fairly consistent from accession to accession. The S. montanum chromosomes were easily identified, and could be distinguished from the seven S. cereale L. chromosomes. Four disomic addition lines of S. montanum accession 2D23 to 'Kharkov M.C. 22' wheat were also analysed and identified.

The chromosomes of Metachirus nudicaudatus (Marsupialia : Didelphidae)

A karyologic study of M. nudicaudatus, carried out on three females and five males, shows a chromosome number of 14, with apparent lack of dimorphism in the sex chromosomes. Nevertheless, the heterochromatin staining technique reveals the Y chromosome to be fully heteropycnotic. The meiotic chromosome has a sex vesicle at the pachytene stage. The similarity of this karyotype with those of Caluromys derbianus and Dromiciops australis is striking, especially considering that the genera belong to two subfamilies separated early in their evolutionary history. Our results support the opinion of Hayman and Martin that the original chromosome number in Marsupialia was 14.