Cytogenetic data showed the enrichment of repetitive DNAs in chromosomal rearrangement points between closely related species in armored catfishes. Still, few studies integrated cytogenetic and ...genomic data aiming to identify their prone-to-break DNA sites. Here, we aimed to obtain the repetitive fraction in Rineloricaria latirostris to recognize the microsatellite and ho-mopolymers flanking the regions previously described as chromosomal fusion points. The results indicated that repetitive DNAs in R. latirostris are predominantly DNA transposons, and considering the microsatellite and homopolymers, A/T-rich expansions were the most abundant. The in situ localization demonstrated the A/T-rich repetitive sequences were scattered on the chromosomes, while A/G-rich microsatellite units were accumulated in some regions. The DNA transposon hAT,the 5S rDNA, and 45S rDNA (previously identified in Robertsonian fusion points in R. latirostris) were clusterized with some mi-crosatellites, especially (CA).sub.n,(GA).sub.n, and poly-A, which were also enriched in regions of chromosomal fusions. Our findings demonstrated that repetitive sequences such as rDNAs, hAT transposons, and microsatellite units flank probable evolutionary breakpoint regions in R. latirostris. However, due to the sequence unit homologies in different chromosomal sites, these repeat DNAs only may facilitate chromosome fusion events in R. latirostris rather than working as a double-strand breakpoint site.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
The Neotropical monophyletic catfish genus Harttia represents an excellent model to study karyotype and sex chromosome evolution in teleosts. Its species split into three phylogenetic clades ...distributed along the Brazilian territory and they differ widely in karyotype traits, including the presence of standard or multiple sex chromosome systems in some members. Here, we investigate the chromosomal rearrangements and associated synteny blocks involved in the origin of a multiple X1X2Y sex chromosome system present in three out of six sampled Amazonian-clade species. Using 5S and 18S ribosomal DNA fluorescence in situ hybridization and whole chromosome painting with probes corresponding to X1 and X2 chromosomes of X1X2Y system from H. punctata, we confirm previous assumptions that X1X2Y sex chromosome systems of H. punctata, H. duriventris and H. villasboas represent the same linkage groups which also form the putative XY sex chromosomes of H. rondoni. The shared homeology between X1X2Y sex chromosomes suggests they might have originated once in the common ancestor of these closely related species. A joint arrangement of mapped H. punctata X1 and X2 sex chromosomes in early diverging species of different Harttia clades suggests that the X1X2Y sex chromosome system may have formed through an X chromosome fission rather than previously proposed Y-autosome fusion.
Charadriiformes, which comprises shorebirds and their relatives, is one of the most diverse avian orders, with over 390 species showing a wide range of karyotypes. Here, we isolated and characterized ...the whole collection of satellite DNAs (satDNAs) at both molecular and cytogenetic levels of one of its representative species, named the wattled jacana (
), a species that contains a typical ZZ/ZW sex chromosome system and a highly rearranged karyotype. In addition, we also investigate the in situ location of telomeric and microsatellite repeats. A small catalog of 11 satDNAs was identified that typically accumulated on microchromosomes and on the W chromosome. The latter also showed a significant accumulation of telomeric signals, being (GA)
the only microsatellite with positive hybridization signals among all the 16 tested ones. These current findings contribute to our understanding of the genomic organization of repetitive DNAs in a bird species with high degree of chromosomal reorganization contrary to the majority of bird species that have stable karyotypes.
The remarkable fish biodiversity encompasses also great sex chromosome variability.
catfish belong to Neotropical models for karyotype and sex chromosome research. Some species possess one of the ...three male-heterogametic sex chromosome systems, XY, X
X
Y or XY
Y
, while other members of the genus have yet uncharacterized modes of sex determination. Particularly the XY
Y
multiple sex chromosome system shows a relatively low incidence among vertebrates, and it has not been yet thoroughly investigated. Previous research suggested two independent X-autosome fusions in
which led to the emergence of XY
Y
sex chromosome system in three of its species. In this study, we investigated evolutionary trajectories of synteny blocks involved in this XY
Y
system by probing six
species with whole chromosome painting (WCP) probes derived from the X (HCA-X) and the chromosome 9 (HCA-9) of
. We found that both painting probes hybridize to two distinct chromosome pairs in Amazonian species, whereas the HCA-9 probe paints three chromosome pairs in
endemic to Guyanese drainages. These findings demonstrate distinct evolutionary fates of mapped synteny blocks and thereby elevated karyotype dynamics in
among the three evolutionary clades.
Harttia comprises an armored catfish genus endemic to the Neotropical region, including 27 valid species with low dispersion rates that are restricted to small distribution areas. Cytogenetics data ...point to a wide chromosomal diversity in this genus due to changes that occurred in isolated populations, with chromosomal fusions and fissions explaining the 2n number variation. In addition, different multiple sex chromosome systems and rDNA loci location are also found in some species. However, several Harttia species and populations remain to be investigated. In this study, Harttia intermontana and two still undescribed species, morphologically identified as Harttia sp. 1 and Harttia sp. 2, were cytogenetically analyzed. Harttia intermontana has 2n = 52 and 2n = 53 chromosomes, while Harttia sp. 1 has 2n = 56 and 2n = 57 chromosomes in females and males, respectively, thus highlighting the occurrence of an XX/XY1Y2 multiple sex chromosome system in both species. Harttia sp. 2 presents 2n = 62 chromosomes for both females and males, with fission events explaining its karyotype diversification. Chromosomal locations of the rDNA sites were also quite different among species, reinforcing that extensive rearrangements had occurred in their karyotype evolution. Comparative genomic hybridization (CGH) experiments among some Harttia species evidenced a shared content of the XY1Y2 sex chromosomes in three of them, thus pointing towards their common origin. Therefore, the comparative analysis among all Harttia species cytogenetically studied thus far allowed us to provide an evolutionary scenario related to the speciation process of this fish group.
The Neotropical genus
Harttia
comprises species with extensive chromosomal remodeling and distinct sex chromosome systems (SCSs). So far, three different SCSs with male heterogamety have been ...characterized in the group. In some species, the presence of the XX/XY
1
Y
2
SCS is associated with a decrease in diploid numbers and several chromosomal rearrangements, although a direct relation to sex chromosome differentiation has not been shown yet. Here, we aimed to investigate the differentiation processes that have led to the establishment of the rare XX/XY
1
Y
2
SCS and track its evolutionary history among other
Harttia
species. For that, four whole chromosome painting probes derived from chromosome 1 of
H. torrenticola
(HTO-1), chromosomes 9 and X of
H. carvalhoi
(HCA-9 and HCA-X), and chromosome X from
H. intermontana
(HIN-X) were applied in nine
Harttia
species. Homeologous chromosome blocks were located in
Harttia
species and demonstrated that Robertsonian (Rb) fusions originated HTO-1, HCA-9, and HCA-X chromosomes, while Rb fissions explain Y
1
and Y
2
sex chromosomes. Specifically, in
H. intermontana
, HCA-X, HCA-9, and the NOR-bearing chromosome demonstrated that homeologous blocks were used in the HIN-X and metacentric pair 2 origins. Consequently, diploid numbers changed between the studied species. Overall, the data also reinforce the existence of unstable genomic sites promoting chromosomal differentiation and remodeling within the genus
Harttia
.
The Neotropical armored catfish genus Harttia presents a wide variation of chromosomal rearrangements among its representatives. Studies indicate that translocation and Robertsonian rearrangements ...have triggered the karyotype evolution in the genus, including differentiation of sex chromosome systems. However, few studies used powerful tools, such as comparative whole chromosome painting, to clarify this highly diversified scenario. Here, we isolated probes from the X1 (a 5S rDNA carrier) and the X2 (a 45S rDNA carrier) chromosomes of Harttia punctata, which displays an X1X1X2X2/X1X2Y multiple sex chromosome system. Those probes were applied in other Harttia species to evidence homeologous chromosome blocks. The resulting data reinforce that translocation events played a role in the origin of the X1X2Y sex chromosome system in H. punctata. The repositioning of homologous chromosomal blocks carrying rDNA sites among ten Harttia species has also been demonstrated. Anchored to phylogenetic data it was possible to evidence some events of the karyotype diversification of the studied species and to prove an independent origin for the two types of multiple sex chromosomes, XX/XY1Y2 and X1X1X2X2/X1X2Y, that occur in Harttia species. The results point to evolutionary breakpoint regions in the genomes within or adjacent to rDNA sites that were widely reused in Harttia chromosome remodeling.
In this work, we trace the dynamics of satellite DNAs (SatDNAs) accumulation and elimination along the pathway of W chromosome differentiation using the well-known Triportheus fish model. Triportheus ...stands out due to a conserved ZZ/ZW sex chromosome system present in all examined species. While the Z chromosome is conserved in all species, the W chromosome is invariably smaller and exhibits differences in size and morphology. The presumed ancestral W chromosome is comparable to that of T. auritus, and contains 19 different SatDNA families. Here, by examining five additional Triportheus species, we showed that the majority of these repetitive sequences were eliminated as speciation was taking place. The W chromosomes continued degeneration, while the Z chromosomes of some species began to accumulate some TauSatDNAs. Additional species-specific SatDNAs that made up the heterochromatic region of both Z and W chromosomes were most likely amplified in each species. Therefore, the W chromosomes of the various Triportheus species have undergone significant evolutionary changes in a short period of time (15–25 Myr) after their divergence.
The plecos (Loricariidae) fish represent a great model for cytogenetic investigations due to their variety of karyotypes, including diploid and polyploid genomes, and different types of sex ...chromosomes. In this study we investigate Transancistrus santarosensis a rare loricariid endemic to Ecuador, integrating cytogenetic methods with specimens’ molecular identification by mtDNA, to describe the the species karyotype. We aim to verify whether sex chromosomes are cytologically identifiable and if they are associated with the accumulation of repetitive sequences present in other species of the family. The analysis of the karyotype (2n = 54 chromosomes) excludes recent centric fusion and pericentromeric inversion and suggests the presence of a ZZ/ZW sex chromosome system at an early stage of differentiation: the W chromosome is degenerated but is not characterized by the presence of differential sex-specific repetitive DNAs. Data indicate that although T. santarosensis has retained the ancestral diploid number of Loricariidae, it accumulated heterochromatin and shows non-syntenic ribosomal genes localization, chromosomal traits considered apomorphic in the family.
Miniature fishes have always been a challenge for cytogenetic studies due to the difficulty in obtaining chromosomal preparations, making them virtually unexplored. An example of this scenario relies ...on members of the family Lebiasinidae which include miniature to medium-sized, poorly known species, until very recently. The present study is part of undergoing major cytogenetic advances seeking to elucidate the evolutionary history of lebiasinids. Aiming to examine the karyotype diversification more deeply in
Pyrrhulina
, here we combined classical and molecular cytogenetic analyses, including Giemsa staining, C-banding, repetitive DNA mapping, comparative genomic hybridization (CGH), and whole chromosome painting (WCP) to perform the first analyses in five
Pyrrhulina
species (
Pyrrhulina
aff.
marilynae
,
Pyrrhulina
sp.,
P. obermulleri
,
P. marilynae
and
Pyrrhulina
cf.
laeta
). The diploid number (2n) ranged from 40 to 42 chromosomes among all analyzed species, but
P. marilynae
is strikingly differentiated by having 2n = 32 chromosomes and a karyotype composed of large meta/submetacentric chromosomes, whose plesiomorphic status is discussed. The distribution of microsatellites does not markedly differ among species, but the number and position of the rDNA sites underwent significant changes among them. Interspecific comparative genome hybridization (CGH) found a moderate divergence in the repetitive DNA content among the species’ genomes. Noteworthy, the WCP reinforced our previous hypothesis on the origin of the X
1
X
2
Y multiple sex chromosome system in
P. semifasciata
. In summary, our data suggest that the karyotype differentiation in
Pyrrhulina
has been driven by major structural rearrangements, accompanied by high dynamics of repetitive DNAs.
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