Papers by Mónica Pradillo
Frontiers in Plant Science
Polyploidization is a common phenomenon in the evolution of flowering plants. However, only a few... more Polyploidization is a common phenomenon in the evolution of flowering plants. However, only a few genes controlling polyploid genome stability, fitness, and reproductive success are known. Here, we studied the effects of loss-of-function mutations in NSE2 and NSE4A subunits of the Structural Maintenance of Chromosomes 5/6 (SMC5/6) complex in autotetraploid Arabidopsis thaliana plants. The diploid nse2 and nse4a plants show partially reduced fertility and produce about 10% triploid offspring with two paternal and one maternal genome copies. In contrast, the autotetraploid nse2 and nse4a plants were almost sterile and produced hexaploid and aneuploid progeny with the extra genome copies or chromosomes coming from both parents. In addition, tetraploid mutants had more severe meiotic defects, possibly due to the presence of four homologous chromosomes instead of two. Overall, our study suggests that the SMC5/6 complex is an important player in the maintenance of tetraploid genome stabil...
Methods in Molecular Biology
The Plant Cell
Structural maintenance of chromosome 5/6 (SMC5/6) complex is a crucial factor for preserving geno... more Structural maintenance of chromosome 5/6 (SMC5/6) complex is a crucial factor for preserving genome stability. Here, we show that mutants for several Arabidopsis (Arabidopsis thaliana) SMC5/6 complex subunits produce triploid offspring. This phenotype is caused by a meiotic defect leading to the production of unreduced male gametes. The SMC5/6 complex mutants show an absence of chromosome segregation during the first and/or the second meiotic division, as well as a partially disorganized microtubule network. Importantly, although the SMC5/6 complex is partly required for the repair of SPO11-induced DNA double-strand breaks, the nonreduction described here is SPO11-independent. The measured high rate of ovule abortion suggests that, if produced, such defects are maternally lethal. Upon fertilization with an unreduced pollen, the unbalanced maternal and paternal genome dosage in the endosperm most likely causes seed abortion observed in several SMC5/6 complex mutants. In conclusion, w...
Scientific Reports
Rubylation is a conserved regulatory pathway similar to ubiquitination and essential in the respo... more Rubylation is a conserved regulatory pathway similar to ubiquitination and essential in the response to the plant hormone auxin. In Arabidopsis thaliana, AUXIN RESISTANT1 (AXR1) functions as the E1-ligase in the rubylation pathway. The gene AXR1-LIKE (AXL), generated by a relatively recent duplication event, can partially replace AXR1 in this pathway. We have analysed mutants deficient for both proteins and complementation lines (with the AXR1 promoter and either AXR1 or AXL coding sequences) to further study the extent of functional redundancy between both genes regarding two processes: meiosis and DNA repair. Here we report that whereas AXR1 is essential to ensure the obligatory chiasma, AXL seems to be dispensable during meiosis, although its absence slightly alters chiasma distribution. In addition, expression of key DNA repair and meiotic genes is altered when either AXR1 or AXL are absent. Furthermore, our results support a significant role for both genes in DNA repair that was not previously described. These findings highlight that AXR1 and AXL show a functional divergence in relation to their involvement in homologous recombination, exemplifying a duplicate retention model in which one copy tends to have more sub-functions than its paralog. Ubiquitination is a post-translational modification pathway that affects a wide variety of processes and is highly conserved among eukaryotes 1-3. Through this process, the small peptide ubiquitin (UBQ) is covalently conjugated to target proteins, altering their stability (by the 26 S proteasome) and activity 4,5. The attachment of UBQ is orchestrated by a cascade of three specialized enzymes: a UBQ-activating enzyme (E1), a UBQ-conjugating enzyme (E2) and a UBQ-ligase protein (E3) 6-11. There are a number of UBQ-like modifiers that utilize similar chemical reactions for covalent ligation to their substrates, such as NEURONAL PRECURSOR CELL EXPRESSED DEVELOPMENTALLY DOWN-REGULATED8 (NEDD8) in animals and fission yeast, known as RELATED TO UBIQUITIN (RUB) in plants. While NEDD8 is encoded by a single copy gene in animals, there are three RUB genes in Arabidopsis thaliana 12 , where RUB1 and RUB2 encode UBQ-RUB fusion proteins 13. RUB closely resembles UBQ and uses a separate but similar E1-E2-E3 biochemical pathway for activation, conjugation, and ligation. In Arabidopsis, the E1 C-TERMINAL-RELATED1 (ECR1) gene encodes the C-terminal RUB E1 subunit, whereas two paralogous genes, AUXIN RESISTANT1 and AXR1-LIKE (AXR1 and AXL, respectively) encode the N-terminal subunits. Following activation, RUB1 CONJUGATING ENZYME1 (RCE1) and RING-BOX 1 (RBX1) act as RUB-conjugating enzyme E2 and RUB-ligase E3, respectively 14-16. Rubylation mainly acts as a regulator of cullin-RING E3 UBQ ligases (CRLs). RUB conjugation stabilizes cullins and produces a change of these E3 UBQ ligases that allows the efficient transfer of UBQ to proteins for degradation 17. Only a few non-cullin substrates have been recently identified, but the biological relevance of these modifications is not yet known (reviewed in Schwechheimer, 2018) 18. Rubylation regulates a wide range of cellular processes in Arabidopsis, including cell cycle progression, light response, vegetative growth, embryo development, and auxin signaling 19-23. In this context, although AXR1 expression is enriched in tissues with high rates of cellular division, in which the importance of DNA repair is critical, the connection of rubylation with DNA damage response has not currently been established in plants 24,25. Nevertheless, several publications have described the importance of this pathway in controlling how cells react to DNA breaks in mice and human cell cultures 26-28. In Arabidopsis, rubylation is also involved in homologous recombination (HR) during meiosis, the specialised cell division that generates gametes 29. HR is a key process during this division, since it ensures bivalent formation.
Journal of Experimental Botany
The nuclear envelope delineates the eukaryotic cell nucleus. The membrane system of the nuclear e... more The nuclear envelope delineates the eukaryotic cell nucleus. The membrane system of the nuclear envelope consists of an outer nuclear membrane and an inner nuclear membrane separated by a perinuclear space. It serves as more than just a static barrier, since it regulates the communication between the nucleoplasm and the cytoplasm and provides the anchoring points where chromatin is attached. Fewer nuclear envelope proteins have been identified in plants in comparison with animals and yeasts. Here, we review the current state of knowledge of the nuclear envelope in plants, focusing on its role as a chromatin organizer and regulator of gene expression, as well as on the modifications that it undergoes to be efficiently disassembled and reassembled with each cell division. Advances in knowledge concerning the mitotic role of some nuclear envelope constituents are also presented. In addition, we summarize recent progress on the contribution of the nuclear envelope elements to telomere t...
Journal of Experimental Botany
Frontiers in Plant Science
The Arabidopsis Book
BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access t... more BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access titles in the biological, ecological, and environmental sciences published by nonprofit societies, associations, museums, institutions, and presses.
Frontiers in Plant Science
Polyploid organisms provide additional opportunities to study meiosis in a more complex context s... more Polyploid organisms provide additional opportunities to study meiosis in a more complex context since more than two potential homologous chromosomes are available. When the chromosome complement of a diploid individual is duplicated, each chromosome is accompanied by one identical and two homologous chromosomes within the same nucleus. In this situation, a competition in pairing/synapsis/chiasma formation between identical and homologous (but not necessarily identical) chromosomes can occur. Several studies have been conducted in different species to address whether there are preferences in crossover formation between identical rather than homologous chromosomes. In this study, multivalent and chiasma frequencies were cytologically analyzed in synthetic autotetraploids of Arabidopsis thaliana including the accessions Col, Ler, and the Col/Ler hybrid. Fluorescence in situ hybridization was conducted to identify each chromosome at metaphase I. The new Col and Ler tetraploids showed high multivalent frequencies, exceeding the theoretical 66.66% expected on a simple random end-pairing model, thus indicating that there are more than two autonomous synaptic sites per chromosome despite their small size. However, a significant excess of bivalent pairs was found in the Col/Ler hybrid, mainly due to the contribution of chromosomes 2 and 3. The mean chiasma frequencies of the three artificial autotetraploids were about twofold the corresponding mean cell chiasma frequencies of their diploid counterparts. The relative contribution of each chromosome to the total chiasma frequency was similar in the three genotypes, with the exception of a lower contribution of chromosome 3 in the hybrid. Preferences for chiasma formation between identical and homologous chromosomes were analyzed in Col/Ler 4x, taking advantage of the cytological differences between the accessions: variations in the size of the 45S rDNA region on the short arm of chromosome 2 and changes in the size and localization of the 5S rDNA region in chromosome 3. We observed a different behavior of chromosomes 2 and 3, i.e., random chiasma formation between identical and homologous chromosomes 2, and preferences for chiasma formation between homologous chromosomes 3. Hence, our results reveal the existence of chromosome-specific mechanisms responsible for these preferences.
Chromosome research : an international journal on the molecular, supramolecular and evolutionary aspects of chromosome biology, Jan 20, 2018
MicroRNAs (miRNAs) are a class of small (containing about 22 nucleotides) single-stranded non-cod... more MicroRNAs (miRNAs) are a class of small (containing about 22 nucleotides) single-stranded non-coding RNAs that regulate gene expression at the post-transcriptional level in plants and animals, being absent from unicellular organisms. They act on diverse key physiological and cellular processes, such as development and tissue differentiation, cell identity, cell cycle progression, and programmed cell death. They are also likely to be involved in a broad spectrum of human diseases. Particularly, this review examines and summarizes work characterizing the function of miRNAs in gametogenesis and fertility. Although numerous studies have elucidated the involvement of reproductive-specific small interfering RNAs (siRNAs) in regulating germ cell development and meiosis, less is known about the role of miRNAs in these processes. We focus on the study of hypomorphic and null alleles of genes encoding components of miRNA biogenesis in both plants (Arabidopsis thaliana) and mammals (Mus muscul...
Methods in molecular biology (Clifton, N.J.), 2017
Plant ARGONAUTE (AGO) proteins regulate a wide range of cellular and developmental functions. Rec... more Plant ARGONAUTE (AGO) proteins regulate a wide range of cellular and developmental functions. Recent findings highlight their role during homologous recombination, a basic mechanism to repair double-strand DNA lesions (in somatic cells) and programmed DNA breaks (in meiocytes). This chapter contains an exhaustive description of procedures applied to analyze meiotic chromosome behavior (cytogenetic techniques) and DNA repair capacity (genotoxicity assays) in AGO-deficient Arabidopsis thaliana mutants.
The Plant cell, 2018
Fanconi anemia (FA) is a human autosomal recessive disorder characterized by chromosomal instabil... more Fanconi anemia (FA) is a human autosomal recessive disorder characterized by chromosomal instability, developmental pathologies, predisposition to cancer, and reduced fertility. So far, 19 genes have been implicated in FA, most of them involved in DNA repair. Some are conserved across higher eukaryotes, including plants. Thegenome encodes a homolog of thegene () whose function in DNA repair is not yet fully understood. Here, we provide evidence thatFANCD2 is required for meiotic homologous recombination. Meiosis is a specialized cell division that ensures reduction of genomic content by half and DNA exchange between homologous chromosomes via crossovers (COs) prior to gamete formation. In plants, a mutation inresults in a 14% reduction of CO numbers. Genetic analysis demonstrated thatacts in parallel to both(), known for its role in promoting interfering COs and(), known for its role in the formation of noninterfering COs.FANCD2 promotes noninterfering COs in a MUS81-independent man...
Frontiers in Plant Science
In eukaryotic organisms, the correct regulation of sister chromatid cohesion, whereby sister chro... more In eukaryotic organisms, the correct regulation of sister chromatid cohesion, whereby sister chromatids are paired and held together, is essential for accurate segregation of the sister chromatids and homologous chromosomes into daughter cells during mitosis and meiosis, respectively. Sister chromatid cohesion requires a cohesin complex comprised of structural maintenance of chromosome adenosine triphosphatases and accessory proteins that regulate the association of the complex with chromosomes or that are involved in the establishment or release of cohesion. The cohesin complex also plays important roles in the repair of DNA double-strand breaks, regulation of gene expression and chromosome condensation. In this review, we summarize progress in understanding cohesion dynamics in plants, with the aim of uncovering differences at specific stages. We also highlight dissimilarities between plants and other eukaryotes with respect to the key players involved in the achievement of cohesion, pointing out areas that require further study.
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...
Frontiers in plant science, 2017
Chromatin Assembly Factor 1 (CAF-1) is an evolutionary conserved heterotrimeric chaperone complex... more Chromatin Assembly Factor 1 (CAF-1) is an evolutionary conserved heterotrimeric chaperone complex that facilitates the incorporation of histones H3 and H4 onto newly synthesized DNA. We demonstrate here that the mutant deficient for the large subunit of the complex, fas1-4, and in minor extent, the mutant deficient for the middle subunit, fas2-1, display chromosome abnormalities throughout Arabidopsis mitosis. Among them, we observed multicentromeric chromosomes at metaphase, and chromatid bridges and acentric fragments at anaphase-telophase. 45S rDNA and telomeric sequences were frequently involved in bridges and fragments. Gene expression analysis by real-time qPCR has revealed that several genes related to homologous recombination (HR) and alternative non-homologous end-joining (aNHEJ) are overexpressed in fas1-4. These results concur with previous studies which have indicated that HR may be involved in the progressive loss of 45S rDNA and telomeres displayed by fas mutants. Howe...
Genetics, Jan 27, 2016
RNA-directed DNA methylation (RdDM) pathway is important for the transcriptional repression of tr... more RNA-directed DNA methylation (RdDM) pathway is important for the transcriptional repression of transposable elements and for heterochromatin formation. Small RNAs are key players in this process throughout a feedback with both DNA and histone methylation. Taking into account that methylation underlies gene silencing and that there are genes with meiosis-specific expression profiles, we have wondered whether genes involved in RdDM could play a role during this specialized cell division. To address this issue we have characterized meiosis progression in pollen mother cells (PMCs) from Arabidopsis thaliana mutant plants defective for several proteins related to RdDM. The most relevant results were obtained for ago4-1 In this mutant, meiocytes display a slight reduction in chiasma frequency, alterations in chromatin conformation around centromeric regions, lagging chromosomes at anaphase I, and defects in spindle organization. These abnormalities lead to the formation of polyads instead...
Frontiers in Plant Science, 2015
Maintenance and precise regulation of sister chromatid cohesion is essential for faithful chromos... more Maintenance and precise regulation of sister chromatid cohesion is essential for faithful chromosome segregation during mitosis and meiosis. Cohesin cofactors contribute to cohesin dynamics and interact with cohesin complexes during cell cycle. One of these, PDS5, also known as SPO76, is essential during mitosis and meiosis in several organisms and also plays a role in DNA repair. In yeast, the complex Wapl-Pds5 controls cohesion maintenance and colocalizes with cohesin complexes into chromosomes. In Arabidopsis, AtWAPL proteins are essential during meiosis, however, the role of AtPDS5 remains to be ascertained. Here we have isolated mutants for each of the five AtPDS5 genes (A-E) and obtained, after different crosses between them, double, triple, and even quadruple mutants (Atpds5a Atpds5b Atpds5c Atpds5e). Depletion of AtPDS5 proteins has a weak impact on meiosis, but leads to severe effects on development, fertility, somatic homologous recombination (HR) and DNA repair. Furthermore, this cohesin cofactor could be important for the function of the AtSMC5/AtSMC6 complex. Contrarily to its function in other species, our results suggest that AtPDS5 is dispensable during the meiotic division of Arabidopsis, although it plays an important role in DNA repair by HR.
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.
Journal of Orthoptera …, 2010
... Hereditas 83: 153162. CrossRef, PubMed. Klásreskâ I., Ramel C. 1978. The effect of methyl me... more ... Hereditas 83: 153162. CrossRef, PubMed. Klásreskâ I., Ramel C. 1978. The effect of methyl mercury hydroxide on meiotic chromosomes of the grasshopper Stethophyma grossum. ... Cited by. Elio Rodrigo Castillo, Dardo Andrea Marti, Claudio Juan Bidau. ...
The Plant journal : for cell and molecular biology, 2015
The movement of chromosomes during meiosis involves location of their telomeres at the inner surf... more The movement of chromosomes during meiosis involves location of their telomeres at the inner surface of the nuclear envelope. Sad1/UNC-84 (SUN) domain proteins are inner nuclear envelope proteins that are part of complexes linking cytoskeletal elements with the nucleoskeleton, connecting telomeres to the force-generating mechanism in the cytoplasm. These proteins play a conserved role in chromosome dynamics in eukaryotes. Homologues of SUN domain proteins have been identified in several plant species. In Arabidopsis thaliana, two proteins that interact with each other, named AtSUN1 and AtSUN2, have been identified. Immunolocalization using antibodies against AtSUN1 and AtSUN2 proteins revealed that they were associated with the nuclear envelope during meiotic prophase I. Analysis of the double mutant Atsun1-1 Atsun2-2 has revealed severe meiotic defects, namely a delay in the progression of meiosis, absence of full synapsis, the presence of unresolved interlock-like structures, and ...
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Papers by Mónica Pradillo