16 research outputs found
Molecular Cytogenetic Analysis of the European Hake Merluccius merluccius (Merlucciidae, Gadiformes): U1 and U2 snRNA Gene Clusters Map to the Same Location
The European hake (Merluccius merluccius) is a highly valuable and intensely fished species
in which a long-term alive stock has been established in captivity for aquaculture purposes.
Due to their huge economic importance, genetic studies on hakes were mostly
focused on phylogenetic and phylogeographic aspects; however chromosome numbers
are still not described for any of the fifteen species in the genus Merluccius. In this work we
report a chromosome number of 2n = 42 and a karyotype composed of three meta/submetacentric
and 18 subtelo/telocentric chromosome pairs. Telomeric sequences appear
exclusively at both ends of every single chromosome. Concerning rRNA genes, this species
show a single 45S rDNA cluster at an intercalary location on the long arm of subtelocentric
chromosome pair 12; the single 5S rDNA cluster is also intercalary to the long arm of chromosome
pair 4. While U2 snRNA gene clusters map to a single subcentromeric position on
chromosome pair 13, U1 snRNA gene clusters seem to appear on almost all chromosome
pairs, but showing bigger clusters on pairs 5, 13, 16, 17 and 19. The brightest signals on
pair 13 are coincident with the single U2 snRNA gene cluster signals. Therefore, the use of
these probes allows the unequivocal identification of at least 7 of the chromosome pairs that
compose the karyotype of Merluccius merluccius thus opening the way to integrate molecular
genetics and cytological data on the study of the genome of this important species.VersiĂłn del editor4,411
The linked units of 5S rDNA and U1 snDNA of razor shells (Mollusca: Bivalvia: Pharidae)
[Abstract] The linkage between 5S ribosomal DNA and other multigene families has been detected in many eukaryote lineages, but whether it provides any selective advantage remains unclear. In this work, we report the occurrence of linked units of 5S ribosomal DNA (5S rDNA) and U1 small nuclear DNA (U1 snDNA) in 10 razor shell species (Mollusca: Bivalvia: Pharidae) from four different genera. We obtained several clones containing partial or complete repeats of both multigene families in which both types of genes displayed the same orientation. We provide a comprehensive collection of razor shell 5S rDNA clones, both with linked and nonlinked organisation, and the first bivalve U1 snDNA sequences. We predicted the secondary structures and characterised the upstream and downstream conserved elements, including a region at â25 nucleotides from both 5S rDNA and U1 snDNA transcription start sites. The analysis of 5S rDNA showed that some nontranscribed spacers (NTSs) are more closely related to NTSs from other species (and genera) than to NTSs from the species they were retrieved from, suggesting birth-and-death evolution and ancestral polymorphism. Nucleotide conservation within the functional regions suggests the involvement of purifying selection, unequal crossing-overs and gene conversions. Taking into account this and other studies, we discuss the possible mechanisms by which both multigene families could have become linked in the Pharidae lineage. The reason why 5S rDNA is often found linked to other multigene families seems to be the result of stochastic processes within genomes in which its high copy number is determinan
FISH of 5S rDNA and telomeric (TTAGGG) n repeats in normal and translocated populations of the frog Quasipaa boulengeri (Anura, Ranidae)
Toxicity of malathion at early life stages of the Senegalese sole, Solea senegalensis (Kaup, 1858): notochord and somatic disruptions
The toxicity of malathion to Solea
senegalensis was studied in a static renewal bioassay for
24, 48 and 72 h, with toxicant concentrations ranging
from 1.56 until 100 ”gL-1. The LC50 values of malathion
for 48 and 72-h was 63.5 (95% C.I: 50.83-79.34) and
22.94 (95% C.I: 17.16-30.68) ”gL-1 respectively. The
survival of larvae was non-affected by exposure to
malathion at concentrations up to 25 ”gL-1 (24 h
NOEC), 6.25 ”gL-1 (48 h NOEC) and <1.6 ”gL-1 (72 h
NOEC). At the end of the experiment, surviving larvae
from concentrations smaller than the 72h-LC50 were
chosen to study morphological changes during malathion
exposure. Results revealed a strong disruption in the
notochord and trunk musculature integrity as a result of
toxicant exposure. Noticeable changes in the
composition and reduction of collagen fibers from the
perinotochordal connective sheath and perimysium were
clearly detected. The trunk musculature was also altered,
showing a general disorganization of fibers. Moreover,
malathion exposure provoked pericardial and yolk-sac
oedemas and histopathological alterations in some other
organ- systems and tissues (i.e. liver, pancreas,
intestine)
Evaluation of the antimicrobial activity of grape extract against Bacillus cereus in rice
The antimicrobial potential of grape extract was assessed in cooked rice against Bacillus cereus. Grape extract efficacy was tested at 1, 5 and 10 mL/L, at pH 4.5, 5.5 and 6.5; and at incubation temperatures simulating different storage scenarios, specifically temperature abuse (10 °C), cool chain break (20 °C) and optimal B. cereus growth temperature (30 °C). Survival curves for grape extract concentration versus time were obtained. The results indicate that antimicrobial activity of grape extract was dependent on temperature, pH and grape extract concentration. A bactericidal effect of the grape extract was shown at concentration levels 5 mL/L at all temperatures and pHs studied. Inactivation curves of B. cereus under grape extract exposure were fitted to a Weibull distribution function for 5â10 mL/L grape extract concentration. Observations showed that the higher the incubation temperature and grape extract concentration, the lower the kinetic rate value. In other words, lower resistance of the microorganism to environmental conditions. The maximum inactivation level was 6 log10 cycles after 24 h of exposure at 10 mL/L of grape extract concentration and pH 4.5. Results indicate that the grape extract could be a good additional control measure for preventing Bacillus cereus growth in cooked rice during storage.TRACE-RICE project, Reference Number AMD-1934-1 and grant PID2020-116318RB-C31, funded by MCIN/AEI/10.13039/501100011033 and âERDF A way of making Europeâ.With funding from the Spanish government through the âSevero Ochoa Centre of Excellenceâ accreditation (CEX2021-001189-S).Peer reviewe
Cytogenetic analysis of the genus Thoropa Cope, 1865 (Anura-Cycloramphidae) with evolutionary inferences based on repetitive sequences
The 5S rDNA in two Abracris grasshoppers (Ommatolampidinae: Acrididae): molecular and chromosomal organization
Systematic analysis and evolution of 5S ribosomal DNA in metazoans
Several studies on 5S ribosomal DNA (5S rDNA) have been focused on a subset of the following features in mostly one organism: number of copies, pseudogenes, secondary structure, promoter and terminator characteristics, genomic arrangements, types of non-transcribed spacers and evolution. In this work, we systematically analyzed 5S rDNA sequence diversity in available metazoan genomes, and showed organism-specific and evolutionary-conserved features. Putatively functional sequences (12 766) from 97 organisms allowed us to identify general features of this multigene family in animals. Interestingly, we show that each mammal species has a highly conserved (housekeeping) 5S rRNA type and many variable ones. The genomic organization of 5S rDNA is still under debate. Here, we report the occurrence of several paralog 5S rRNA sequences in 58 of the examined species, and a flexible genome organization of 5S rDNA in animals. We found heterogeneous 5S rDNA clusters in several species, supporting the hypothesis of an exchange of 5S rDNA from one locus to another. A rather high degree of variation of upstream, internal and downstream putative regulatory regions appears to characterize metazoan 5S rDNA. We systematically studied the internal promoters and described three different types of termination signals, as well as variable distances between the coding region and the typical termination signal. Finally, we present a statistical method for detection of linkage among noncoding RNA (ncRNA) gene families. This method showed no evolutionary-conserved linkage among 5S rDNAs and any other ncRNA genes within Metazoa, even though we found 5S rDNA to be linked to various ncRNAs in several clades