Molecular cytogenetic investigation based on fluorescence in situ hybridization (FISH) of the scleractinian coral, Echinophyllia aspera Ellis and Solander 1788, which is commonly found along temperate coasts in Japan (30-35°N) and in coastal waters in the Indian and Pacific oceans, was performed. FISH was applied in the study of this coral, using E. aspera embryo (about 9-12 hours after artificial fertilization; prawn chip stage). By genomic DNA hybridization (GDH) using DNA that was extracted from E. aspera embryos, we have succeeded in displaying the characteristic and distinct heterochromatin distribution, especially on telomeric regions of chromosomes, which may facilitate the classification of corals. FISH mapping of rRNA genes (rDNAs) was successfully carried out with the probe generated by PCR amplification using rRNA gene primers and revealed that extraordinary amplification of rDNA occurred in one of the homologous chromosomes similar to that in a homogeneous staining region (hsr) that is sometimes seen in human cancer cells. The presence of telomere sequences, (TTAGGG)n, in all chromosomes was visualized and demonstrated that this coral had the same sequences as humans. Based on these results obtained by FISH, we proposed the karyotype of this coral (2n = 28). Furthermore, we found that the telomeric heterochromatin in this coral contained the human satellite III DNA motif sequence (TTCCA)n, which is located on human chromosome 9 centromere. Taken together, these data suggest that karyotyping, rRNA gene mapping and heterochromatin motif sequences are useful tools for exploring the process of chromosome evolution, and phylogenetics of scleractinian coral.
Twelve populations of Anthemis tinctoria L. (yellow camomile) medicinal plant belonging to the tribe Anthemideae within the family Compositae, from different Iranian origins were studied in aspect of cytogenetical marker. Root tips were examined for karyological studies. Chromosome counts from 12 populations confirm the base chromosome number at x=9 with numerous 2n=2x=18 diploids. The most chromosomes in all populations were metacentric and a few chromosomes were sub-metacentric and were located in Stebbins classes (SC) 1A. The mean length of total chromosome varied from 5.414 μm in A. tinctoria-1 (Kordestan, Baneh) to 7.205 μm in A. tinctoria-9 (East Azerbaijan, Garacheman). In addition, A. tinctoria-10 (West Azerbaijan, Sardasht) with the highest of A1, A2 (interachromosomal, interchromosal asymmetry index), AR (Arm Ratio) and L% (Relative Length of Long Arm) had karyotype heterogeneity. The results of principal components analysis (PCA) and cluster analysis (Ward) based on chromosomal characteristics and karyotype asymmetry, categorized the twelve populations separated into three groups. This finding may provide useful information for Anthemis tinctoria evolutionary, genetic and breeding studies.
Karyotype and distribution of C-band-positive constitutive heterochromatin and silver-positive nucleolus organizer regions (Ag-NORs) were studied in an anemonefish, Amphiprion perideraion. This species had the diploid chromosome number of 48 consisting of 6 pairs of metacentric, 13 pairs of submetacentric and 5 pairs of subtelo- or acrocentric chromosomes, and the fundamental number was calculated as 86. The karytotype of this species was very similar to those of A. clarkii and A. frenatus already reported, but C-bands and Ag-NORs showed different distribution among the three species. The present study demonstrated that C-bands and Ag-NORs were useful markers to distinguish very similar karyotypes of the three anemonefishes.