Cytoplasmic and genomic effects on meiotic pairing in Brassica hybrids and allotetraploids from pair crosses of three cultivated diploids.
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ABSTRACT:
SUBMITTER: Cui C
PROVIDER: S-EPMC3389969 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Nuclear-cytoplasmic interactions are predicted to be important in shaping the genetic changes in early stage of allopolyploidization. Our previous study shows the specific role of genome and cytoplasm affecting the chromosome pairing in Brassica hybrids and allotetraploids from pairwise crosses between three cultivated diploids with A, B and C genomes, respectively. Herein, to address how parental genomes and cytoplasm affects genomic, epigenetic and gene expression changes prior to meiosis in these hybrids and allopolyploids, their patterns of AFLP (Amplified fragment length polymorphism), mAFLP (Methylation AFLP) and cDNA-AFLP were compared with the progenitors, revealing the major absent bands within each genome. These changes varied under various cytoplasm backgrounds and genome combinations, following the significant order of AFLP> mAFLP> cDNA -AFLP. The frequencies of AFLP bands lost were positively correlated with the divergence degrees of parental genomes, but not obvious for those of mAFLP and cDNA-AFLP absent bands, and methylation change showed least variations among hybrids and within each genome. These changes within each genome followed the A>B>C hierarchy, except the highest rate of cDNA loss in B genome. Among three changes, only overall AFLP bands were significantly correlated with cDNA-AFLP, and their correlations varied within each genome. These changes in allotetraploids were mainly caused by genome merger rather than doubling. Parental genomes altered differently at three levels, responded to the types of cytoplasm and genome and their interaction or divergence. The result provides new clues for instant non-meiosis-driven genome restructuring following genome merger and duplication.
| S-EPMC3669095 | biostudies-literature
Project description:Polyploidy is popular for the speciation of angiosperms but the initial stage of allopolyploidization resulting from interspecific hybridization and genome duplication is associated with different extents of changes in genome structure and gene expressions. Herein, the transcriptomes detected by RNA-seq in resynthesized Brassica allotetraploids (Brassica juncea, AABB; B. napus, AACC; B. carinata, BBCC) from the pair-wise crosses of the same three diploids (B. rapa, AA; B. nigra, BB; B. oleracea, CC) were compared to reveal the patterns of gene expressions from progenitor genomes and the effects of different types of genome combinations and cytoplasm, upon the genome merger and duplication. From transcriptomic analyses for leaves and silique walls, extensive expression alterations were revealed in these resynthesized allotetraploids relative to their diploid progenitors, as well as during the transition from vegetative to reproductive development, for differential and transgressive gene expressions were variable in numbers and functions. Genes involved in glucosinolates and DNA methylation were transgressively up-regulated among most samples, suggesting that gene expression regulation was immediately established after allopolyploidization. The expression of ribosomal protein genes was also tissue-specific and showed a similar expression hierarchy of rRNA genes. The balance between the co-up and co-down regulation was observed between reciprocal B. napus with different types of the cytoplasm. Our results suggested that gene expression changes occurred after initial genome merger and such profound alterations might enhance the growth vigor and adaptability of Brassica allotetraploids.
| S-EPMC4631939 | biostudies-literature
Project description:Disentangling phylogenetic relationships proves challenging for groups that have evolved recently, especially if there is ongoing reticulation. Although they are in most cases immediately isolated from diploid relatives, sets of sibling allopolyploids often hybridize with each other, thereby increasing the complexity of an already challenging situation. Dactylorhiza (Orchidaceae: Orchidinae) is a genus much affected by allopolyploid speciation and reticulate phylogenetic relationships. Here, we use genetic variation at tens of thousands of genomic positions to unravel the convoluted evolutionary history of Dactylorhiza. We first investigate circumscription and relationships of diploid species in the genus using coalescent and maximum likelihood methods, and then group 16 allotetraploids by maximum affiliation to their putative parental diploids, implementing a method based on genotype likelihoods. The direction of hybrid crosses is inferred for each allotetraploid using information from maternally inherited plastid RADseq loci. Starting from age estimates of parental taxa, the relative ages of these allotetraploid entities are inferred by quantifying their genetic similarity to the diploids and numbers of private alleles compared with sibling allotetraploids. Whereas northwestern Europe is dominated by young allotetraploids of postglacial origins, comparatively older allotetraploids are distributed further south, where climatic conditions remained relatively stable during the Pleistocene glaciations. Our bioinformatics approach should prove effective for the study of other naturally occurring, nonmodel, polyploid plant complexes.
| S-EPMC6902629 | biostudies-literature
Project description:The sunflower hybrids hold a narrow cytoplasmic diversity. Besides, the heterotic effect of wild cytoplasmic combinations of sunflower on important traits under water stress has not been explored in detail. Here, we evaluated the different sunflower cytoplasmic combinations in sunflower hybrids using cytoplasmic male sterile (CMS) sources as female parents. We used a total of sixteen sunflower genotypes representing twelve CMS lines from wild and conventional sources along with four restorer lines. Twelve CMS lines were crossed with four restorer lines to develop a total of 48 F1 hybrid combinations. The hybrids were evaluated under two different environments (i.e., regular irrigation and water stress) for morphophysiological, yield, and biochemical traits over two years. Heterotic effect for various CMS sources was evaluated on all of the three possible scales, namely, better-parent heterosis (BPH), mid-parent heterosis (MPH), and heterosis as percent of check (PSH-996). For better-parent and mid-parent heterosis, the CMS sources Helianthus annuus, Helianthus argophyllus, and Helianthus debilis demonstrated positive better-parent heterosis for seed yield, oil content, and oleic acid irrespective of the environment. However, the hybrid combinations of different sources when using the genotype RCR8297 as the restorer parent recorded maximum average returns. Furthermore, chlorophyll meter (SPAD) reading positively correlated with days to 50% flowering, days to maturity, plant height, and number of leaves per plant in both the environments. Overall, this study identified and compared the heterotic effect of the different cytoplasmic combinations in sunflower under water stress as well as under normal irrigation environments.
| S-EPMC7238153 | biostudies-literature
Project description:A period of pairing between nonhomologous centromeres occurs early in meiosis in a diverse collection of organisms. This early, homology-independent, centromere pairing, referred to as centromere coupling in budding yeast, gives way to an alignment of homologous centromeres as homologues synapse later in meiotic prophase. The regulation of centromere coupling and its underlying mechanism have not been elucidated. In budding yeast, the protein Zip1p is a major component of the central element of the synaptonemal complex in pachytene of meiosis, and earlier, is essential for centromere coupling. The experiments reported here demonstrate that centromere coupling is mechanistically distinct from synaptonemal complex assembly. Zip2p, Zip3p, and Red1p are all required for the assembly of Zip1 into the synaptonemal complex but are dispensable for centromere coupling. However, the meiotic cohesin Rec8p is required for centromere coupling. Loading of meiotic cohesins to centromeres and cohesin-associated regions is required for the association of Zip1 with these sites, and the association of Zip1 with the centromeres then promotes coupling. These findings reveal a mechanism that promotes associations between centromeres before the assembly of the synaptonemal complex, and they demonstrate that chromosomes are preloaded with Zip1p in a manner that may promote synapsis.
| S-EPMC2877639 | biostudies-literature
Project description:Although organisms belonging to different species and subspecies sometimes produce fertile offspring, a hallmark of the speciation process is reproductive isolation, characterized by hybrid sterility (HS) due to failure in gametogenesis. In mammals, HS is usually exhibited by males, the heterogametic sex. The phenotypic manifestations of HS are complex. The most frequently observed are abnormalities in both autosomal and sex chromosome interactions that are linked to meiotic prophase arrest or postmeiotic spermiogenesis aberrations and lead to defective or absent gametes. The aim of this study was to determine the HS phenotypes in intersubspecific F1 mice produced by matings between Mus musculus molossinus-derived strains and diverse Mus musculus domesticus-inbred laboratory mouse strains. Most of these crosses produced fertile F1 offspring. However, when female BALB/cJ (domesticus) mice were mated to male JF1/MsJ (molossinus) mice, the (BALBdomxJF1mol)F1 males were sterile, whereas the (JF1molxBALBdom)F1 males produced by the reciprocal crossings were fertile; thus the sterility phenotype was asymmetric. The sterile (BALBdomxJF1mol) F1 males exhibited a high rate of meiotic metaphase arrest with misaligned chromosomes, probably related to a high frequency of XY dissociation. Intriguingly, in the sterile (BALBdomxJF1mol)F1 males we observed aberrant allele-specific expression of several meiotic genes, that play critical roles in important meiotic events including chromosome pairing. Together, these observations of an asymmetrical HS phenotype in intersubspecific F1 males, probably owing to meiotic defects in the meiotic behavior of the XY chromosomes pair and possibly also transcriptional misregulation of meiotic genes, provide new models and directions for understanding speciation mechanisms in mammals.
| S-EPMC6399516 | biostudies-literature
Project description:Allopolyploidy, combining interspecific hybridization with whole genome duplication, has had significant impact on plant evolution. Its evolutionary success is related to the rapid and profound genome reorganizations that allow neoallopolyploids to form and adapt. Nevertheless, how neoallopolyploid genomes adapt to regulate their expression remains poorly understood. The hypothesis of a major role for small noncoding RNAs (sRNAs) in mediating the transcriptional response of neoallopolyploid genomes has progressively emerged. Generally, 21-nt sRNAs mediate posttranscriptional gene silencing by mRNA cleavage, whereas 24-nt sRNAs repress transcription (transcriptional gene silencing) through epigenetic modifications. Here, we characterize the global response of sRNAs to allopolyploidy in Brassica, using three independently resynthesized Brassica napus allotetraploids originating from crosses between diploid Brassica oleracea and Brassica rapa accessions, surveyed at two different generations in comparison with their diploid progenitors. Our results suggest an immediate but transient response of specific sRNA populations to allopolyploidy. These sRNA populations mainly target noncoding components of the genome but also target the transcriptional regulation of genes involved in response to stresses and in metabolism; this suggests a broad role in adapting to allopolyploidy. We finally identify the early accumulation of both 21- and 24-nt sRNAs involved in regulating the same targets, supporting a posttranscriptional gene silencing to transcriptional gene silencing shift at the first stages of the neoallopolyploid formation. We propose that reorganization of sRNA production is an early response to allopolyploidy in order to control the transcriptional reactivation of various noncoding elements and stress-related genes, thus ensuring genome stability during the first steps of neoallopolyploid formation.
| S-EPMC6445299 | biostudies-literature
Project description:Brassica includes many successfully cultivated crop species of polyploid origin, either by ancestral genome triplication or by hybridization between two diploid progenitors, displaying complex repetitive sequences and transposons. The U's triangle, which consists of three diploids and three amphidiploids, is optimal for the analysis of complicated genomes after polyploidization. Next-generation sequencing enables the transcriptome profiling of polyploids on a global scale.We examined the gene expression patterns of three diploids (Brassica rapa, B. nigra, and B. oleracea) and three amphidiploids (B. napus, B. juncea, and B. carinata) via digital gene expression analysis. In total, the libraries generated between 5.7 and 6.1 million raw reads, and the clean tags of each library were mapped to 18547-21995 genes of B. rapa genome. The unambiguous tag-mapped genes in the libraries were compared. Moreover, the majority of differentially expressed genes (DEGs) were explored among diploids as well as between diploids and amphidiploids. Gene ontological analysis was performed to functionally categorize these DEGs into different classes. The Kyoto Encyclopedia of Genes and Genomes analysis was performed to assign these DEGs into approximately 120 pathways, among which the metabolic pathway, biosynthesis of secondary metabolites, and peroxisomal pathway were enriched. The non-additive genes in Brassica amphidiploids were analyzed, and the results indicated that orthologous genes in polyploids are frequently expressed in a non-additive pattern. Methyltransferase genes showed differential expression pattern in Brassica species.Our results provided an understanding of the transcriptome complexity of natural Brassica species. The gene expression changes in diploids and allopolyploids may help elucidate the morphological and physiological differences among Brassica species.
| S-EPMC4312607 | biostudies-literature
Project description:BACKGROUND:Cytokinin is a classical phytohormone that plays important roles in numerous plant growth and development processes. In plants, cytokinin signals are transduced by a two-component system, which involves many genes, including cytokinin response factors (CRFs). Although CRFs take vital part in the growth of Arabidopsis thaliana and Solanum lycopersicum, little information of the CRFs in the Brassica U-triangle species has been known yet. RESULTS:We identified and compared 141 CRFs in the diploids and amphidiploids of Brassica species, including B. rapa, B. oleracea, B. nigra, B. napus, and B. juncea. For all the 141 CRFs, the sequence and structure analysis, physiological and biochemical characteristics analysis were performed. Meanwhile, the Ka/Ks ratios of orthologous and paralogous gene pairs were calculated, which indicated the natural selective pressure upon the overall length or a certain part of the CRFs. The expression profiles of CRFs in different tissues and under various stresses were analyzed in B. oleracea, B. nigra, and B. napus. The similarities and differences in gene sequences and expression profiles among the homologous genes of these species were discussed. In addition, AtCRF11 and its ortholog BrCRF11a were identified to be related to primary root growth in Arabidopsis. CONCLUSION:This study performed a genome-wide comparative analysis of the CRFs in the diploids and amphidiploids of the Brassica U-triangle species. Many similarities and differences in gene sequences and expression profiles existed among the CRF homologous genes of these species. In the bioinformatics analysis, we found the close relativity of the CRF homologous genes in the Brassica A and C genomes and the distinctiveness of those in the B genome, and the CRF homologous genes in B subgenome were considerably influenced by the A subgenome of B. juncea. In addition, we identified a new function of the Clade V CRFs related to root growth, which also clarified the functional conservation between Arabidopsis and B. rapa. These results not only offer useful information on the functional analysis of CRFs but also provide new insights into the evolution of Brassica species.
| S-EPMC6171139 | biostudies-literature
Project description:Meiotic chromosome pairing involves not only recognition of homology but also juxtaposition of entire chromosomes in a topologically regular way. Analysis of filamentous fungus Sordaria macrospora reveals that recombination proteins Mer3, Msh4, and Mlh1 play direct roles in all of these aspects, in advance of their known roles in recombination. Absence of Mer3 helicase results in interwoven chromosomes, thereby revealing the existence of features that specifically ensure "entanglement avoidance." Entanglements that remain at zygotene, i.e., "interlockings," require Mlh1 for resolution, likely to eliminate constraining recombinational connections. Patterns of Mer3 and Msh4 foci along aligned chromosomes show that the double-strand breaks mediating homologous alignment have spatially separated ends, one localized to each partner axis, and that pairing involves interference among developing interhomolog interactions. We propose that Mer3, Msh4, and Mlh1 execute all of these roles during pairing by modulating the state of nascent double-strand break/partner DNA contacts within axis-associated recombination complexes.
| S-EPMC2851631 | biostudies-literature