Project description:How allopolyploids are able not only to cope but profit from their condition is a question that remain elusive, but of great importance within the wide context of successful hybrid polyploid evolution. One outstanding example of successful allopolyploidy is the endemic Iberian S. alburnoides fish complex. Previously, based on the evaluation of 7 genes, it was reported that the transcription levels between diploid and triploid hybrid S. alburnoides were similar. If this phenomenon would occur on a full genomic scale, a wide functional diploidization could be related to the success of polyploids. We generated RNA-seq data from whole juvenile fish and from an adult tissue, to perform the first comparative quantitative transcriptomic analysis between ploidy levels of a vertebrate allopolyploid. We found 64% in juvenilesM-b full body samples and 44% in liver samples of similar expression between diploid and triploid hybrids, and those genes are mostly involved in processes of basal biological maintenance of the cells. Yet, respectively only 29% and 15% of transcripts presented accurate dosage compensation. Therefore, an exact functional diploidization of the triploid genome does not occur, but globally a significant down regulation of gene expression in triploids was observed. We find that for those genes which show similar expression levels in diploids and triploids, expression in triploids is not globally strictly proportional to gene dosage nor is it set to a perfect diploid level. This quantitative flexibility of expression may be a strong contributor to overcome the 'genomic shock', and be an immediate evolutionary advantage of allopolyploids. Genotypes: Squalius alburnoides is an allopolyploid cyprinid, resulting from interspecific hybridization between females of Squalius pyrenaicus (P genome) and males of a now extinct species related to Anaecypris hispanica (A genome). S. alburnoides natural populations arecomposed of animals of different ploidy levels and genomic constitutions (different genotypes). The predominant S. alburnoides complex intervenients in the Iberian Peninsula southern rivers are the hybrid triploid PAA, diploid PA, the parental-like diploid AA and the parental species S. pyrenaicus PP.
Project description:Common wheat is an allohexaploid species, derived through endoreduplication of an inter-specific triploid hybrid produced from a cross between cultivated tetraploid wheat and the wild diploid relative Aegilops tauschii Coss. Hybrid incompatibilities, including hybrid necrosis, have been observed in triploid wheat hybrids. A limited number of Ae. tauschii accessions show hybrid lethality in triploid hybrids crossed with tetraploid wheat due to developmental arrest at the early seedling stage, which is termed severe growth abortion (SGA). Despite the potential severity of this condition, the genetic mechanisms underlying SGA are not well understood. We conducted comparative analyses of gene expression profiles in crown tissues to characterize developmental arrest in triploid hybrids displaying SGA. A number of defense-related genes were highly up-regulated, whereas many transcription factor genes, such as the KNOTTED1-type homeobox gene, which function in shoot apical meristem (SAM) and leaf primordia, were down-regulated in the crown tissues of SGA plants. Transcript accumulation levels of cell cycle-related genes were also markedly reduced in SGA plants, and no histone H4-expressing cells were observed in the SAM of SGA hybrid plants. Our findings demonstrate that SGA shows unique features among other types of abnormal growth phenotypes, such as type II and III necrosis.
Project description:The systematic deep sequencing analysis provided a comprehensive understanding of the transcriptome complexity of 2n and 3n Fujian oyster. This information broadens our understanding of the mechanisms of C.angulata polyploidization and contributes to molecular and genetic research by enriching the oyster database. This is the first report on genome-wide transcriptional analysis of adductor muscle of diploid and triploid Fujian oyster and has demonstrated triploid oysters are morphologically almost identical to their diploid counterparts, but have faster growth, due to the reorientation of energetic allocation from gametogenesis to somatic investment. This study provides a foundation for further analysis of the gene expression patterns and signaling pathways which regulate the molecular mechanisms of diploid and triploid oyster.
Project description:The systematic deep sequencing analysis provided a comprehensive understanding of the transcriptome complexity of 2n and 3n Fujian oyster. This information broadens our understanding of the mechanisms of C.angulata polyploidization and contributes to molecular and genetic research by enriching the oyster database. This is the first report on genome-wide transcriptional analysis of adductor muscle of diploid and triploid Fujian oyster and has demonstrated triploid oysters are morphologically almost identical to their diploid counterparts, but have faster growth, due to the reorientation of energetic allocation from gametogenesis to somatic investment. This study provides a foundation for further analysis of the gene expression patterns and signaling pathways which regulate the molecular mechanisms of diploid and triploid oyster. Examination of 3 different samples, including diploid (DF and DM) and triplod(T) oyster.
Project description:To avoid negative environmental impacts of escapees and potential inter-breeding with wild populations, the Atlantic salmon farming industry has and continues to extensively test triploid fish that are sterile. However, they often show differences in performance, physiology, behavior and morphology compared to diploid fish, with increased prevalence of vertebral deformities and ocular cataracts as two of the most severe disorders. Here, we investigated the mechanisms behind the higher prevalence of cataracts in triploid salmon, by comparing the transcriptional patterns in lenses of diploid and triploid Atlantic salmon, with and without cataracts. We assembled and characterized the Atlantic salmon lens transcriptome and used RNA-seq to search for the molecular basis for cataract development in triploid fish. Transcriptional screening showed only modest differences in lens mRNA levels in diploid and triploid fish, with few uniquely expressed genes. In total, there were 165 differentially expressed genes (DEGs) between the cataractous diploid and triploid lens. Of these, most were expressed at lower levels in triploid fish. Differential expression was observed for genes encoding proteins with known function in the retina (phototransduction) and proteins associated with repair and compensation mechanisms. The results suggest a higher susceptibility to oxidative stress in triploid lenses, and that mechanisms connected to the ability to handle damaged proteins are differentially affected in cataractous lenses from diploid and triploid salmon.
Project description:Heterosis and polyploidy are two important aspects of plant evolution. To examine these issues, we conducted a global gene expression study of a maize ploidy series as well as a set of tetraploid inbred and hybrid lines. This gene expression analysis complements an earlier phenotypic study of these same materials. We find that ploidy change affects a large fraction of the genome, albeit at low levels; gene expression changes rarely exceed 2-fold and are typically not statistically significant. The most common gene expression profile we detected is greater than linear increase from monoploid to diploid, and reductions from diploid to triploid and from triploid to tetraploid, a trend that mirrors plant stature. When examining heterosis in tetraploid maize lines, we found a large fraction of the genome impacted but the majority of changes were not statistically significant at 2-fold or less. Non-additive expression was common in the hybrids, and the extent of non-additivity increased both in number and magnitude from duplex to quadruplex hybrids. Overall, we find that gene expression trends mirror observations from the phenotypic studies; however, obvious mechanistic connections remain unknown. We examined gene expression in a ploidy series (1n to 4n) of the maize line B73 and in a variety of hybrid tetraploid lines using a complex loop design. Pooled RNA samples from 10 plants were used (2 independent RNA isolations/sample), and all comparisons were made using replicate dye swaps (16 slide sets/comparison). For the ploidy analysis, all expression changes were computed relative to the diploid as well as between 2n + 3n and 3n + 4n. For the expression analysis of hybrids, hybrid expression levels were compared to the parental expression levels as well as to mid-parent levels.