Nieves Cuñado - Academia.edu (original) (raw)
Papers by Nieves Cuñado
Plants
Heat stress alters the number and distribution of meiotic crossovers in wild and cultivated plant... more Heat stress alters the number and distribution of meiotic crossovers in wild and cultivated plant species. Hence, global warming may have a negative impact on meiosis, fertility, and crop productions. Assessment of germplasm collections to identify heat-tolerant genotypes is a priority for future crop improvement. Durum wheat, Triticum turgidum, is an important cultivated cereal worldwide and given the genetic diversity of the durum wheat Spanish landraces core collection, we decided to analyse the heat stress effect on chiasma formation in a sample of 16 landraces of T. turgidum ssp. turgidum and T. turgidum ssp. durum, from localities with variable climate conditions. Plants of each landrace were grown at 18–22 °C and at 30 °C during the premeiotic temperature-sensitive stage. The number of chiasmata was not affected by heat stress in three genotypes, but decreased by 0.3–2 chiasmata in ten genotypes and more than two chiasmata in the remaining three ones. Both thermotolerant and ...
A heterochromatic satellite DNA is highly amplified in a single chromosome of Muscari (Hyacinthac... more A heterochromatic satellite DNA is highly amplified in a single chromosome of Muscari (Hyacinthaceae)
Methods in Molecular Biology, 2019
An improved method of preparing two-dimensional surface spreads of synaptonemal complexes (SCs) i... more An improved method of preparing two-dimensional surface spreads of synaptonemal complexes (SCs) in higher plants for examination by electron microscopy is described. This protocol produces clear, well-spread preparations of SCs and unpaired axial cores from a range of meiotic prophase I stages (leptotene to pachytene) from meiocytes of different plant species. Synaptonemal complex (SC) analyses have been widely used in plant cytogenetic studies to address the process of meiotic chromosome synapses, because of the high-resolution allowed by electron microscopy. Although the real role of SC is still enigmatic, its presence and structural conservation in the vast majority of organisms reflect the importance of this protein structure in the meiotic process.
Scientific reports, Jan 24, 2017
MicroRNAs (miRNAs) are ~22-nt single-stranded noncoding RNAs with regulatory roles in a wide rang... more MicroRNAs (miRNAs) are ~22-nt single-stranded noncoding RNAs with regulatory roles in a wide range of cellular functions by repressing eukaryotic gene expression at a post-transcriptional level. Here, we analyzed the effects on meiosis and fertility of hypomorphic or null alleles of the HYL1, HEN1, DCL1, HST and AGO1 genes, which encode miRNA-machinery components in Arabidopsis. Reduced pollen and megaspore mother cell number and fertility were shown by the mutants analyzed. These mutants also exhibited a relaxed chromatin conformation in male meiocytes at the first meiotic division, and increased chiasma frequency, which is likely to be due to increased levels of mRNAs from key genes involved in homologous recombination. The hen1-13 mutant was found to be hypersensitive to gamma irradiation, which mainly causes double-strand breaks susceptible to be repaired by homologous recombination. Our findings uncover a role for miRNA-machinery components in Arabidopsis meiosis, as well as in...
Plant Systematics and Evolution, 2000
In the subgenusLeopoldia of the genusMuscari, M. comosum is an exceptional species because it pre... more In the subgenusLeopoldia of the genusMuscari, M. comosum is an exceptional species because it presents the most asymmetrical karyotype of the group and because its only active NOR is located in the fifth chromosome pair, while in the other species it is located in the first or second chromosome pairs (all the species have 2n = 18 chromosomes). SinceM. comosum
Canadian Journal of Genetics and Cytology, 1986
Nucleoli and nucleolar organizer regions (NORs) have been studied by a silver staining method in ... more Nucleoli and nucleolar organizer regions (NORs) have been studied by a silver staining method in all meiotic stages of wheat–rye hybrid plants. The maximum number of nucleoli per cell scored at meiotic prophase and tapetum binucleate cells indicates that only the NORs of 1B, 6B, and 5D wheat chromosomes are active, whereas that of chromosome IR (SAT) of rye is inactive. However, at diakinesis, metaphase and anaphase meiotic stages only chromosomes 1B and 6B show Ag-NOR as was reported previously in somatic metaphase. The absence of Ag-NOR on chromosome 5D has been imputed to its low nucleolar organizer activity, not detectable by silver staining, because of the small number of rDNA clusters it carries. On the other hand, the meiotic behaviour of chromosomes 1B and 6B has been studied at metaphase I and anaphase I, using the Ag-NORs as cytological markers.Key words: nucleolar organizer, Ag-NOR, meiosis, wheat–rye hybrids.
Theoretical and Applied Genetics, 1992
Theoretical and Applied Genetics, 1992
Theoretical and Applied Genetics, 1985
The Plant Journal, 2011
The eukaryotic recombinases RAD51 and DMC1 are essential for DNA strand-exchange between homologo... more The eukaryotic recombinases RAD51 and DMC1 are essential for DNA strand-exchange between homologous chromosomes during meiosis. RAD51 is also expressed during mitosis, and mediates homologous recombination (HR) between sister chromatids. It has been suggested that DMC1 might be involved in the switch from intersister chromatid recombination in somatic cells to interhomolog meiotic recombination. At meiosis, the Arabidopsis Atrad51 null mutant fails to synapse and has extensive chromosome fragmentation. The Atdmc1 null mutant is also asynaptic, but in this case chromosome fragmentation is absent. Thus in plants, AtDMC1 appears to be indispensable for interhomolog homologous recombination, whereas AtRAD51 seems to be more involved in intersister recombination. In this work, we have studied a new AtRAD51 knock-down mutant, Atrad51-2, which expresses only a small quantity of RAD51 protein. Atrad51-2 mutant plants are sterile and hypersensitive to DNA double-strand break induction, but their vegetative development is apparently normal. The meiotic phenotype of the mutant consists of partial synapsis, an elevated frequency of univalents, a low incidence of chromosome fragmentation and multivalent chromosome associations. Surprisingly, non-homologous chromosomes are involved in 51% of bivalents. The depletion of AtDMC1 in the Atrad51-2 background results in the loss of bivalents and in an increase of chromosome fragmentation. Our results suggest that a critical level of AtRAD51 is required to ensure the fidelity of HR during interchromosomal exchanges. Assuming the existence of asymmetrical DNA strand invasion during the initial steps of recombination, we have developed a working model in which the initial step of strand invasion is mediated by AtDMC1, with AtRAD51 required to check the fidelity of this process.
The Plant Cell, 2014
Meiotic recombination is the fundamental process that produces balanced gametes and generates div... more Meiotic recombination is the fundamental process that produces balanced gametes and generates diversity within species. For successful meiosis, crossovers must form between homologous chromosomes. This condition is more difficult to fulfill in allopolyploid species, which have more than two sets of related chromosomes (homoeologs). Here, we investigated the formation, progression, and completion of several key hallmarks of meiosis in Brassica napus (AACC), a young polyphyletic allotetraploid crop species with closely related homoeologous chromosomes. Altogether, our results demonstrate a precocious and efficient sorting of homologous versus homoeologous chromosomes during early prophase I in two representative B. napus accessions that otherwise show a genotypic difference in the progression of homologous recombination. More strikingly, our detailed comparison of meiosis in near isogenic allohaploid and euploid plants showed that the mechanism(s) promoting efficient chromosome sortin...
Planta, 2013
Different histone modifications often modify DNA-histone interactions affecting both local and gl... more Different histone modifications often modify DNA-histone interactions affecting both local and global structure of chromatin, thereby providing a vast potential for functional responses. Most studies have focused on the role of several modifications in gene transcription regulation, being scarce on other aspects of eukaryotic chromosome structure during cell division, mainly in meiosis. To solve this issue we have performed a cytological analysis to determine the chromosomal distribution of several histone H3 modifications throughout all phases of both mitosis and meiosis in different plant species. We have chosen Aegilops sp. and Secale cereale (monocots) and Arabidopsis thaliana (dicots) because they differ in their phylogenetic affiliation as well as in content and distribution of constitutive heterochromatin. In the species analyzed, the patterns of H3 acetylation and methylation were held constant through mitosis, including modifications associated with "open chromatin". Likewise, the immunolabeling patterns of H3 methylation remained invariable throughout meiosis in all cases. On the contrary, there was a total loss of acetylated H3 immunosignals on condensed chromosomes in both meiotic divisions, but only in monocot species. Regarding the phosphorylation of histone H3 at Ser10, present on condensed chromosomes, although we did not observe any difference in the dynamics, we found slight differences between the chromosomal distribution of this modification between Arabidopsis and cereals (Aegilops sp. and rye). Thus far, in plants chromosome condensation throughout cell division appears to be associated with a particular combination of H3 modifications. Moreover, the distribution and dynamics of these modifications seem to be species-specific and even differ between mitosis and meiosis in the same species.
Genetics, 2007
During first meiotic prophase, homologous chromosomes are normally kept together by both crossove... more During first meiotic prophase, homologous chromosomes are normally kept together by both crossovers and synaptonemal complexes (SC). In most eukaryotes, the SC disassembles at diplotene, leaving chromosomes joined by chiasmata. The correct co-orientation of bivalents at metaphase I and the reductional segregation at anaphase I are facilitated by chiasmata and sister-chromatid cohesion. In the absence of meiotic reciprocal recombination, homologs are expected to segregate randomly at anaphase I. Here, we have analyzed the segregation of homologous chromosomes at anaphase I in four meiotic mutants of Arabidopsis thaliana, spo11-1-3, dsy1, mpa1, and asy1, which show a high frequency of univalents at diplotene. The segregation pattern of chromosomes 2, 4, and 5 was different in each mutant. Homologous univalents segregated randomly in spo11-1-3, whereas they did not in dsy1 and mpa1. An intermediate situation was observed in asy1. Also, we have found a parallelism between this behavior ...
Cytogenetic and Genome Research, 2012
In the Squalius alburnoides fish complex, allotriploid females (3n = 75) reproduce mostly by meio... more In the Squalius alburnoides fish complex, allotriploid females (3n = 75) reproduce mostly by meiotic hybridogenesis, producing haploid gametes by means of the elimination of the heterospecific chromosome set and recombination between the 2 homospecific genomes. A synaptonemal complexes (SCs) analysis was performed in specimens from a confined southern population (Quarteira, Portugal) to understand chromosome dynamics during gametogenesis. The comparative study between hybrid females with QAA genome composition and the parental bisexual species Squalius aradensis (2n = 50, QQ genome) evidenced: (i) that allotriploid meiocytes comprise the complete chromosome set (75 chromosomes) in prophase I, proving the heterospecific genome (Q) is only excluded after pachytene stage, and (ii) a 2-phase synaptic process where initially, exclusively homologous SCs form and the unmatched univalents remain in a bouquet conformation, followed by the establishment of extensive non-homologous SCs with mu...
Chromosome Research, 1998
Characterization of sex chromosomes in males of Mantis religiosa L. (2n = 24 + X1X2Y) was carried... more Characterization of sex chromosomes in males of Mantis religiosa L. (2n = 24 + X1X2Y) was carried out by C-banding, silver staining and fluorescence in situ hybridization. They are meta- or submetacentric, their arms being designated as X1L, X1R, X2R, X2L, YL and YR. Meiotic behaviour of the sex trivalent was examined through the analysis of synaptonemal complexes (SCs), prometaphase
Genomic insights from the Squalius alburnoides complex in the confined Quarteira drainage populat... more Genomic insights from the Squalius alburnoides complex in the confined Quarteira drainage population: what’s new?
Plants
Heat stress alters the number and distribution of meiotic crossovers in wild and cultivated plant... more Heat stress alters the number and distribution of meiotic crossovers in wild and cultivated plant species. Hence, global warming may have a negative impact on meiosis, fertility, and crop productions. Assessment of germplasm collections to identify heat-tolerant genotypes is a priority for future crop improvement. Durum wheat, Triticum turgidum, is an important cultivated cereal worldwide and given the genetic diversity of the durum wheat Spanish landraces core collection, we decided to analyse the heat stress effect on chiasma formation in a sample of 16 landraces of T. turgidum ssp. turgidum and T. turgidum ssp. durum, from localities with variable climate conditions. Plants of each landrace were grown at 18–22 °C and at 30 °C during the premeiotic temperature-sensitive stage. The number of chiasmata was not affected by heat stress in three genotypes, but decreased by 0.3–2 chiasmata in ten genotypes and more than two chiasmata in the remaining three ones. Both thermotolerant and ...
A heterochromatic satellite DNA is highly amplified in a single chromosome of Muscari (Hyacinthac... more A heterochromatic satellite DNA is highly amplified in a single chromosome of Muscari (Hyacinthaceae)
Methods in Molecular Biology, 2019
An improved method of preparing two-dimensional surface spreads of synaptonemal complexes (SCs) i... more An improved method of preparing two-dimensional surface spreads of synaptonemal complexes (SCs) in higher plants for examination by electron microscopy is described. This protocol produces clear, well-spread preparations of SCs and unpaired axial cores from a range of meiotic prophase I stages (leptotene to pachytene) from meiocytes of different plant species. Synaptonemal complex (SC) analyses have been widely used in plant cytogenetic studies to address the process of meiotic chromosome synapses, because of the high-resolution allowed by electron microscopy. Although the real role of SC is still enigmatic, its presence and structural conservation in the vast majority of organisms reflect the importance of this protein structure in the meiotic process.
Scientific reports, Jan 24, 2017
MicroRNAs (miRNAs) are ~22-nt single-stranded noncoding RNAs with regulatory roles in a wide rang... more MicroRNAs (miRNAs) are ~22-nt single-stranded noncoding RNAs with regulatory roles in a wide range of cellular functions by repressing eukaryotic gene expression at a post-transcriptional level. Here, we analyzed the effects on meiosis and fertility of hypomorphic or null alleles of the HYL1, HEN1, DCL1, HST and AGO1 genes, which encode miRNA-machinery components in Arabidopsis. Reduced pollen and megaspore mother cell number and fertility were shown by the mutants analyzed. These mutants also exhibited a relaxed chromatin conformation in male meiocytes at the first meiotic division, and increased chiasma frequency, which is likely to be due to increased levels of mRNAs from key genes involved in homologous recombination. The hen1-13 mutant was found to be hypersensitive to gamma irradiation, which mainly causes double-strand breaks susceptible to be repaired by homologous recombination. Our findings uncover a role for miRNA-machinery components in Arabidopsis meiosis, as well as in...
Plant Systematics and Evolution, 2000
In the subgenusLeopoldia of the genusMuscari, M. comosum is an exceptional species because it pre... more In the subgenusLeopoldia of the genusMuscari, M. comosum is an exceptional species because it presents the most asymmetrical karyotype of the group and because its only active NOR is located in the fifth chromosome pair, while in the other species it is located in the first or second chromosome pairs (all the species have 2n = 18 chromosomes). SinceM. comosum
Canadian Journal of Genetics and Cytology, 1986
Nucleoli and nucleolar organizer regions (NORs) have been studied by a silver staining method in ... more Nucleoli and nucleolar organizer regions (NORs) have been studied by a silver staining method in all meiotic stages of wheat–rye hybrid plants. The maximum number of nucleoli per cell scored at meiotic prophase and tapetum binucleate cells indicates that only the NORs of 1B, 6B, and 5D wheat chromosomes are active, whereas that of chromosome IR (SAT) of rye is inactive. However, at diakinesis, metaphase and anaphase meiotic stages only chromosomes 1B and 6B show Ag-NOR as was reported previously in somatic metaphase. The absence of Ag-NOR on chromosome 5D has been imputed to its low nucleolar organizer activity, not detectable by silver staining, because of the small number of rDNA clusters it carries. On the other hand, the meiotic behaviour of chromosomes 1B and 6B has been studied at metaphase I and anaphase I, using the Ag-NORs as cytological markers.Key words: nucleolar organizer, Ag-NOR, meiosis, wheat–rye hybrids.
Theoretical and Applied Genetics, 1992
Theoretical and Applied Genetics, 1992
Theoretical and Applied Genetics, 1985
The Plant Journal, 2011
The eukaryotic recombinases RAD51 and DMC1 are essential for DNA strand-exchange between homologo... more The eukaryotic recombinases RAD51 and DMC1 are essential for DNA strand-exchange between homologous chromosomes during meiosis. RAD51 is also expressed during mitosis, and mediates homologous recombination (HR) between sister chromatids. It has been suggested that DMC1 might be involved in the switch from intersister chromatid recombination in somatic cells to interhomolog meiotic recombination. At meiosis, the Arabidopsis Atrad51 null mutant fails to synapse and has extensive chromosome fragmentation. The Atdmc1 null mutant is also asynaptic, but in this case chromosome fragmentation is absent. Thus in plants, AtDMC1 appears to be indispensable for interhomolog homologous recombination, whereas AtRAD51 seems to be more involved in intersister recombination. In this work, we have studied a new AtRAD51 knock-down mutant, Atrad51-2, which expresses only a small quantity of RAD51 protein. Atrad51-2 mutant plants are sterile and hypersensitive to DNA double-strand break induction, but their vegetative development is apparently normal. The meiotic phenotype of the mutant consists of partial synapsis, an elevated frequency of univalents, a low incidence of chromosome fragmentation and multivalent chromosome associations. Surprisingly, non-homologous chromosomes are involved in 51% of bivalents. The depletion of AtDMC1 in the Atrad51-2 background results in the loss of bivalents and in an increase of chromosome fragmentation. Our results suggest that a critical level of AtRAD51 is required to ensure the fidelity of HR during interchromosomal exchanges. Assuming the existence of asymmetrical DNA strand invasion during the initial steps of recombination, we have developed a working model in which the initial step of strand invasion is mediated by AtDMC1, with AtRAD51 required to check the fidelity of this process.
The Plant Cell, 2014
Meiotic recombination is the fundamental process that produces balanced gametes and generates div... more Meiotic recombination is the fundamental process that produces balanced gametes and generates diversity within species. For successful meiosis, crossovers must form between homologous chromosomes. This condition is more difficult to fulfill in allopolyploid species, which have more than two sets of related chromosomes (homoeologs). Here, we investigated the formation, progression, and completion of several key hallmarks of meiosis in Brassica napus (AACC), a young polyphyletic allotetraploid crop species with closely related homoeologous chromosomes. Altogether, our results demonstrate a precocious and efficient sorting of homologous versus homoeologous chromosomes during early prophase I in two representative B. napus accessions that otherwise show a genotypic difference in the progression of homologous recombination. More strikingly, our detailed comparison of meiosis in near isogenic allohaploid and euploid plants showed that the mechanism(s) promoting efficient chromosome sortin...
Planta, 2013
Different histone modifications often modify DNA-histone interactions affecting both local and gl... more Different histone modifications often modify DNA-histone interactions affecting both local and global structure of chromatin, thereby providing a vast potential for functional responses. Most studies have focused on the role of several modifications in gene transcription regulation, being scarce on other aspects of eukaryotic chromosome structure during cell division, mainly in meiosis. To solve this issue we have performed a cytological analysis to determine the chromosomal distribution of several histone H3 modifications throughout all phases of both mitosis and meiosis in different plant species. We have chosen Aegilops sp. and Secale cereale (monocots) and Arabidopsis thaliana (dicots) because they differ in their phylogenetic affiliation as well as in content and distribution of constitutive heterochromatin. In the species analyzed, the patterns of H3 acetylation and methylation were held constant through mitosis, including modifications associated with "open chromatin". Likewise, the immunolabeling patterns of H3 methylation remained invariable throughout meiosis in all cases. On the contrary, there was a total loss of acetylated H3 immunosignals on condensed chromosomes in both meiotic divisions, but only in monocot species. Regarding the phosphorylation of histone H3 at Ser10, present on condensed chromosomes, although we did not observe any difference in the dynamics, we found slight differences between the chromosomal distribution of this modification between Arabidopsis and cereals (Aegilops sp. and rye). Thus far, in plants chromosome condensation throughout cell division appears to be associated with a particular combination of H3 modifications. Moreover, the distribution and dynamics of these modifications seem to be species-specific and even differ between mitosis and meiosis in the same species.
Genetics, 2007
During first meiotic prophase, homologous chromosomes are normally kept together by both crossove... more During first meiotic prophase, homologous chromosomes are normally kept together by both crossovers and synaptonemal complexes (SC). In most eukaryotes, the SC disassembles at diplotene, leaving chromosomes joined by chiasmata. The correct co-orientation of bivalents at metaphase I and the reductional segregation at anaphase I are facilitated by chiasmata and sister-chromatid cohesion. In the absence of meiotic reciprocal recombination, homologs are expected to segregate randomly at anaphase I. Here, we have analyzed the segregation of homologous chromosomes at anaphase I in four meiotic mutants of Arabidopsis thaliana, spo11-1-3, dsy1, mpa1, and asy1, which show a high frequency of univalents at diplotene. The segregation pattern of chromosomes 2, 4, and 5 was different in each mutant. Homologous univalents segregated randomly in spo11-1-3, whereas they did not in dsy1 and mpa1. An intermediate situation was observed in asy1. Also, we have found a parallelism between this behavior ...
Cytogenetic and Genome Research, 2012
In the Squalius alburnoides fish complex, allotriploid females (3n = 75) reproduce mostly by meio... more In the Squalius alburnoides fish complex, allotriploid females (3n = 75) reproduce mostly by meiotic hybridogenesis, producing haploid gametes by means of the elimination of the heterospecific chromosome set and recombination between the 2 homospecific genomes. A synaptonemal complexes (SCs) analysis was performed in specimens from a confined southern population (Quarteira, Portugal) to understand chromosome dynamics during gametogenesis. The comparative study between hybrid females with QAA genome composition and the parental bisexual species Squalius aradensis (2n = 50, QQ genome) evidenced: (i) that allotriploid meiocytes comprise the complete chromosome set (75 chromosomes) in prophase I, proving the heterospecific genome (Q) is only excluded after pachytene stage, and (ii) a 2-phase synaptic process where initially, exclusively homologous SCs form and the unmatched univalents remain in a bouquet conformation, followed by the establishment of extensive non-homologous SCs with mu...
Chromosome Research, 1998
Characterization of sex chromosomes in males of Mantis religiosa L. (2n = 24 + X1X2Y) was carried... more Characterization of sex chromosomes in males of Mantis religiosa L. (2n = 24 + X1X2Y) was carried out by C-banding, silver staining and fluorescence in situ hybridization. They are meta- or submetacentric, their arms being designated as X1L, X1R, X2R, X2L, YL and YR. Meiotic behaviour of the sex trivalent was examined through the analysis of synaptonemal complexes (SCs), prometaphase
Genomic insights from the Squalius alburnoides complex in the confined Quarteira drainage populat... more Genomic insights from the Squalius alburnoides complex in the confined Quarteira drainage population: what’s new?