Derived karyotypes in two elephantfish genera (Hyperopisus and Pollimyrus): lowest chromosome number in the family Mormyridae (Osteoglossiformes)

The African weakly electric elephantfish family Mormyridae comprises 22 genera and almost 230 species. Up-to-date cytogenetic information was available for 17 species representing 14 genera. Here we report chromosome number and morphology in Hyperopisus bebe (Lacepède, 1803) and Pollimyrus isidori (Valenciennes, 1847) collected from the White Nile system in southwestern Ethiopia. Both taxa displayed the diploid chromosome number 2n = 40, but they differed in fundamental numbers: FN = 66 in H. bebe and FN = 72 in P. isidori; previously the same diploid chromosome number 2n = 40 was reported in an undescribed species of Pollimyrus Taverne, 1971 (FN = 42) from the same region. Our results demonstrate that not only pericentric inversions, but fusions also played a substantial role in the evolution of the mormyrid karyotype structure. If the hypothesis that the karyotype structure with 2n = 50–52 and prevalence of the uni-armed chromosomes close to the ancestral condition for the family Mormyridae is correct, the most derived karyotype structures are found in the Mormyrus Linnaeus, 1758 species with 2n = 50 and the highest number of bi-armed elements in their compliments compared to all other mormyrids and in Pollimyrus isidori with the highest number of bi-armed elements among the mormyrids with 2n = 40.

Karyotype structure and cytogenetic markers of Amoimyrmex bruchi and Amoimyrmex silvestrii: the contribution to understanding leafcutting ant relationships

Leafcutting ants are considered the most important herbivores in terrestrial environments throughout the Neotropics. <i>Amoimyrmex</i> is the sister clade of the remaining leafcutter ants from the genera <i>Atta</i> and <i>Acromyrmex</i>. <i>Amoimyrmex striatus</i> was the only species cytogenetically studied within the genus and shares the same chromosomal number with <i>Atta</i>, bearing 22 chromosomes, whereas <i>Acromyrmex</i> bears 38 chromosomes, with the exception of the social parasite <i>Acromyrmex ameliae</i> (2n=36). Our objective here was to analyze cytogenetically the species of <i>Amoimyrmex bruchi</i> and <i>Amoimyrmex silvestrii</i>, as well as to describe the karyotype of these sister species, by means of an integrative approach using classical and molecular cytogenetics. We aimed to characterize cytogenetic markers that contribute to the systematics and taxonomy of the genus. Our results showed that the karyotypes of these two species are very similar, with an identical chromosome number (2n=22), chromosome morphology (2K=20m+2sm), and location of 18S rDNA and the telomeric repeat TTAGG on the chromosomes. Yet, the microsatellite probe GA(15) showed variation across the species and populations studied. We suggest that both species diverged relatively recently and are unmistakably sisters because of the many shared characteristics, including the highly conserved karyotypes.

Genome-wide Identification and Transcriptional Profiling of New Cobra-like Genes in Bread Wheat (Triticum Aestivum)

Background: The COBL gene encodes a plant-specific glycosylphosphatidylinositol (GPI)-anchored protein. Recently identified COBRA genes supposed as a key regulator of the orientation of cell expansion in the root indicating that Cobra gene family members are likely to be important new players at the plasma membrane-cell wall interface. Methods and Results: By performing a database search and domain prediction, we identified five genes named as TaCOBL 1, TaCOBL 2, TaCOBL 3, TaCOBL 4 and TaCOBL 5, and selected for further analysis. Chromosomal locations of each gene were drawn on karyotype. Structure of genes, promoter analysis and phylogenetic analysis were done using bioinformatics tools and databases. Set of novel SNPs were also predicted. Gene ontologies were analyzed, and pathways involving cobra genes were predicted. Whole genes of 3kb to 4kb were successfully amplified. Five set of primers were designed targeting TaCOBL 1, TaCOBL 2, TaCOBL 3 TaCOBL 4 and TaCOBL 5 genes. Expression of COBL genes were checked in root and shoot by using qPCR. The qRT-PCR revealed that expression TaCOBL genes can be regulated under abiotic stress such drought stress. Conclusion: The comprehensive annotation and expression profiling of COBL genes performed in this study enhanced our understanding and these genes were found to play a significant role in drought stress. Our findings lay the groundwork for further functional investigation of COBL genes mechanism.

Chromosome and Molecular Analyses Reveal Significant Karyotype Diversity and Provide New Evidence on the Origin of Aegilops columnaris

Aegilops columnaris Zhuk. is tetraploid grass species (2n = 4x = 28, UcUcXcXc) closely related to Ae. neglecta and growing in Western Asia and a western part of the Fertile Crescent. Genetic diversity of Ae. columnaris was assessed using C-banding, FISH, nuclear and chloroplast (cp) DNA analyses, and gliadin electrophoresis. Cytogenetically Ae. columnaris was subdivided into two groups, C-I and C-II, showing different karyotype structure, C-banding, and FISH patterns. C-I group was more similar to Ae. neglecta. All types of markers revealed significant heterogeneity in C-II group, although group C-I was also polymorphic. Two chromosomal groups were consistent with plastogroups identified in a current study based on sequencing of three chloroplast intergenic spacer regions. The similarity of group C-I of Ae. columnaris with Ae. neglecta and their distinctness from C-II indicate that divergence of the C-I group was associated with minor genome modifications. Group C-II could emerge from C-I relatively recently, probably due to introgression from another Aegilops species followed by a reorganization of the parental genomes. Most C-II accessions were collected from a very narrow geographic region, and they might originate from a common ancestor. We suggest that the C-II group is at the initial stage of species divergence and undergoing an extensive speciation process.

Chromosome and Molecular Analyses Reveal Significant Intraspecific Karyotype Diversity and Provide New Evidence on the Origin of Tetraploid Grass Aegilops columnaris

Aegilops columnaris Zhuk. is tetraploid grass species (2n=4x=28, UcUcXcXc) closely related to Ae. neglecta and growing in Western Asia and a western part of the Fertile Crescent. Genetic diversity of Ae. columnaris was assessed using C-banding, FISH, nuclear and chloroplast (cp)DNA analyses, and gliadin electrophoresis. Cytogenetically Ae. columnaris was subdivided into two groups, C-I and C-II, showing different karyotype structure, C-banding and FISH patterns. Group C-I was more similar to Ae. neglecta. All types of markers revealed significant heterogeneity of the C-II group, although group C-I was also polymorphic. Two chromosomal groups were consistent with plastogroups identified in a current study based on sequencing of three chloroplast intergenic spacer regions. The similarity of group C-I of Ae. columnaris with Ae. neglecta and their distinctness from C-II indicate that divergence of the C-I group was associated with minor genome modifications. Group C-II could emerge from C-I relatively recently, probably due to introgression from another Aegilops species followed by a reorganization of the parental genomes. Most C-II accessions were collected from the very narrow geographic region, and they might originate from a common ancestor. We suggest that the C-II group is at the initial stage of species divergence and undergoing an extensive speciation process.

Chromosome analysis in Saccodon wagneri (Characiformes) and insights into the karyotype evolution of Parodontidae

ABSTRACT Parodontidae is a relatively small group of Neotropical characiform fishes consisting of three genera (Apareiodon, Parodon, and Saccodon) with 32 valid species. A vast cytogenetic literature is available on Apareiodon and Parodon, but to date, there is no cytogenetic data about Saccodon, a genus that contains only three species with a trans-Andean distribution. In the present study the karyotype of S. wagneri was described, based on both conventional (Giemsa staining, Ag-NOR, C-bands) and molecular (repetitive DNA mapping by fluorescent in situ hybridization) methods. A diploid chromosome number of 2n = 54 was observed in both sexes, and the presence of heteromorphic sex chromosomes of the ZZ/ZW type was detected. The W chromosome has a terminal heterochromatin band that occupies approximately half of the long arm, being this band approximately half the size of the Z chromosome. The FISH assay showed a synteny of the 18S-rDNA and 5S-rDNA genes in the chromosome pair 14, and the absence of interstitial telomeric sites. Our data reinforce the hypothesis of a conservative karyotype structure in Parodontidae and suggest an ancient origin of the sex chromosomes in the fishes of this family.

First cytogenetic information for five Nilotic elephantfishes and a problem of ancestral karyotype of the family Mormyridae (Osteoglossiformes)

The elephantfish family Mormyridae is the most diverse lineage of the primitive teleostean clade Osteoglossomorpha distributed in inland waters of all continents except Antarctica and Europe. The family Mormyridae is endemic to Africa and includes 22 genera and almost 230 species. The evolutionary radiation of mormyrids most probably should be attributed to their capability of both generating and receiving weak electric signals. Up-to-date cytogenetic studies have revealed substantial karyotype differentiation among the nine investigated elephantfish species and genera (a single species studied per each genus). In the present study, karyotypes of five species representing five mormyrid genera (four unexplored ones) collected from the White Nile system in southwestern Ethiopia are described for the first time. The results show substantial variety of the diploid chromosome and fundamental numbers: 2n = 48 and FN = 54 in Brevimyrus niger (Günther, 1866), 2n = 50 and FN = 72 in Cyphomyrus petherici (Boulenger, 1898), 2n = 50 and FN = 78 in Hippopotamyrus pictus (Marcusen, 1864), 2n = 50 and FN = 76 in Marcusenius cyprinoides (Linnaeus, 1758), 2n = 52 and FN = 52 in Mormyrops anguilloides (Linnaeus, 1758). Karyotype structure in the latter species seems to be close to the ancestral condition for the family. This hypothesis is discussed in the light of available data on karyotype diversity and phylogeny of mormyrids.