Project description:We profiled the gene regulatory landscape of Brassica napus reproductive development using RNA sequencing. Comparative analysis of this nascent allotetraploid across the plant lifecycle revealed the contribution of each subgenome to plant reproduction. Global mRNA profiling across reproductive development revealed lower accumulation of C subgenome transcripts relative to the A subgenome. Subgenome-specific transcriptional networks identified distinct transcription factor families enriched in each of the A and C subgenome in early seed development. Analysis of a tissue specific transcriptome of early seed development revealed transcription factors predicted to be regulators encoded by the A subgenome are expressed primarily in the seed coat whereas regulators encoded by the C subgenome were expressed primarily in the embryo. Whole genome transcription factor networks identified BZIP11 as an essential regulator of early B. napus seed development. Knockdown of BZIP11 using RNA interference resulted in knockdown of predicted target genes, and a reproductive-lethal phenotype. Our data indicate that subgenome bias are characteristic features of the B. napus seed throughout its development, and that such bias might not be universal across the embryo, endosperm, and seed coat of the developing seed. We also find that examining transcriptional networks spanning both the A and C genomes of the whole B. napus seed can identify valuable targets for seed development research. We suggest that-omics level approaches to studying gene regulation in B. napus can benefit from both broad and high-resolution analyses.
Project description:The importance and applications of polyploidy have long been recognized, from shaping the evolutionary success of flowering plants to improving agricultural productivity. Recent studies have shown that one of the parental subgenomes in ancient polyploids is generally more dominant - having both retained more genes and being more highly expressed - a phenomenon termed subgenome dominance. How quickly one subgenome dominates within a newly formed polyploid, if immediate or after millions of years, and the genomic features that determine which genome dominates remain poorly understood. To investigate the rate of subgenome dominance emergence, we examined gene expression, gene methylation, and transposable element (TE) methylation in a natural less than 140 year old allopolyploid (Mimulus peregrinus), a resynthesized interspecies triploid hybrid (M. robertsii), a resynthesized allopolyploid (M. peregrinus), and diploid progenitors (M. guttatus and M. luteus). We show that subgenome expression dominance occurs instantly following the hybridization of two divergent genomes and that subgenome expression dominance significantly increases over generations. Additionally, CHH methylation levels are significantly reduced in regions near genes and within transposons in the first generation hybrid, intermediate in the resynthesized allopolyploid, and are repatterned differently between the dominant and submissive subgenomes in the natural allopolyploid. Our analyses reveal that the subgenome differences in levels of TE methylation mirror the increase in expression bias observed over the generations following the hybridization. These findings not only provide important insights into genomic and epigenomic shock that occurs following hybridization and polyploid events, but may also contribute to uncovering the mechanistic basis of heterosis and subgenomic dominance.
Project description:The fate of doubled genes, from allopolyploid or autopolyploid origin, is controlled at multiple levels within the central dogma: gene loss or silencing, neo- and/or sub functionalization, inter genomic transfer, allele dominance/co-dominance, differences in transcription/translation efficiency, post translational modifications… These regulatory processes through evolution have caused a plethora of genotype x environment interactions displayed in the modern day phenotypes. The study of non-model crops is challenging but solutions are emerging. More and more, one gets insight into the tolerance mechanisms of a specific genotype. By integrating transcriptomics into our proteomic data, we studied the genetic diversity of an allopolyploid ABB banana, a tolerant genotype, and compared it to two different sensitive AAA genotypes. The root growth of the ABB cultivar was 60 % higher under mild osmotic stress. 234,000 spectra were aligned and quantified, resulting in 2,753 identified root proteins. 383 gene loci displayed genotype specific differential expression whereof 252 showed at least one Single Amino Acid Polymorphism (SAAP). The homeoallelic contribution was assessed using transcriptome read alignment, thus revealing each allele contribution at the RNA level. This provides insight in the structure and the organization of the triploid genome. In the ABB cultivar, allele expressions are supposed to follow a 1/3 and 2/3 pattern. We found that many genes deviated from this expectation and we show that 32 gene loci even displayed a 100% read preference for the allele that was unique for the ABB tolerant genotype , suggesting that the presence of unique alleles and homoelog expression bias is correlated to the observed phenotype.
Project description:Time course of gene expression profiles during seed development and maturation in Brassica napus were studied using Combimatrix Brassica microarray. The time course expression of 90K Brassica napus EST contigs were measured at 8 developing seed stages of 10, 15, 20, 25, 30, 35, 40 and 45 DAF (days after flowering) using single color microarray
Project description:Time course of gene expression profiles during seed development and maturation in Brassica napus were studied using Combimatrix Brassica microarray.
Project description:Seed coat colour is determined by the type of pigment deposited in the seed coat cells. It is related to important agronomic traits of seeds, such as seed dormancy, longevity, oil content, protein content and fibre content. In Brassica napus, inheritance of seed coat colour is related to maternal effects and pollen effects (xenia effects). In this research, we isolated a mutation of yellow seeded B. napus controlled by a single Mendelian locus with pollen effect. Microcopy of transverse sections of the mature seed shows pigment is deposited only in the epidermal cells, the first cell layer of seed coat. By Illumina Hiseq 2000 sequencing technology, a total of 12 G clean data, 116x coverage of coding sequences of B. napus, was achieved from 26-day old brown and yellow seeds. It was assembled into 172,238 independent transcripts and 55,637 unigenes by Trinity. A total of 150 orthologous genes of Arabidopsis transparent testa (TT) genes were mapped in silico to 19 chromosomes of B. napus. Only 49 of the TT orthologous genes are transcripted in seeds. However transcription of all the orthologs was independent of the embryonal control of seed coat colour. Of all the Trinity-assembled unigenes, only 55 genes were found to be differentially expressed between the brown seeds and yellow mutant. Among them 50 were up-regulated and 5 were down-regulated in the yellow seeds as compared to the brown counterpart. By KEGG classification, 14 metabolic pathways were enriched significantly. Of these, 5 pathways: phenylpropanoid biosynthesis, cyanoamino acid metabolism, plant hormone signal transduction, metabolic pathways and biosynthesis of secondary metabolites, were related with seed coat pigmentation. Free amino acid quantification showed that Ala and Phe were produced at higher levels in the embryo of yellow seeds as compared to brown seeds. This increase was not observed in the seed coat. Moreover, the excess amount of free Ala was exactly twice that of Phe in the 26-day embryo of yellow seeds. Pigment indispensable substrate chalcone is synthesized from two molecules of Ala and one molecule of Phe. The correlation between accumulation of Ala and Phe and disappearance of pigment in the yellow seeded mutant indicate that embryonal control of seed coat colour is related with Phe and Ala metabolism in the embryo of B. napus.
Project description:Background: Polyploidy has long been recognized as an important mechanism in eukaryotes evolution. Recent studies have documented dynamic changes in plant polyploid gene expression, which reflects genomic and functional plasticity of duplicate genes and genomes in plants. Genomewide approaches in a variety of allopolyploids, mostly synthetics, reveal a trend of non-additive gene expression. The aim of the study was to document expression divergence between a relatively recently formed natural allopolyploid (Coffea arabica) and its ancestral parents (Coffea canephora and Coffea eugenioides) and to verify if the divergence was ‘environment-dependent’.Results: Employing a microarray platform designed against 15,522 unigenes, we assayed gene expression levels in allopolyploid and its two parental diploids. For each gene, we determined expression variation levels between the three species grown under two sets of temperature conditions (26-22°C/30-26°C). More than 35% of genes were differentially expressed in each comparison at both temperatures, except for ‘allopolyploid versus Canephora’ at the ‘hottest’ temperature where an unexpected low gene expression divergence (<9%) were observed. Genes were binned in categories: ‘no change’, ‘additivity’, ‘transgressive’ and ‘dominance’ (‘Canephora-like’ and ‘Eugenioides-like’). The totally new phenomenon revealed by our study was a drastic modification of proportions between the allopolyploid and its parents when environmental conditions were modified. At the ‘hottest’ temperature, we found a virtual disappearance of gene categories classed as ‘transgressive’, ‘Eugenioides-like dominance’ or ‘additivity’ and a major increase in genes classed in the ‘Canephora-like dominance’ category. At this set of growing conditions, we therefore found very high bias that suggested a phenomenon of ‘dominance’ of C. canephora transcription profile. The Canephora genome parental expression state seems exhibited in strong preference to the Eugenioides genome parental state. Conclusion: Our data constitute evidence for a transcription profile divergence between allopolyploid and its parental species, massively affected by environmental conditions. The parental origin of the transcription profiles was not consistently biased towards one parental species, but appeared to be affected by environmental conditions. This phenomenon indicates the plasticity of allopolyploids and might ultimately explain better adaptation to environmental conditions.
Project description:Although utilization of heterosis has largely improved the yield of many crops worldwide, the underlying molecular mechanism of heterosis, particularly for allopolyploids, remains unclear. Here, we compared epigenome and transcriptome data of an elite hybrid and its parental lines in three assessed tissues (seedling, flower bud, and silique) to explore their contribution to heterosis in allopolyploid B. napus. Transcriptome analysis illustrated that a small proportion of non-additive genes in the hybrid compared with its parents, as well as parental expression level dominance, might have a significant effect on heterosis. We identified histone modification (H3K4me3 and H3K27me3) variation between the parents and hybrid, most of which resulted from the differences between parents. H3K4me3 variations were positively correlated with gene expression differences among the hybrid and its parents. Furthermore, H3K4me3 and H3K27me3 were rather stable in hybridization and were mainly inherited additively in the B. napus hybrid. Together, our data revealed that transcriptome reprogramming and histone modification remodeling in the hybrid could serve as valuable resources for better understanding heterosis in allopolyploid crops.
Project description:A critical barrier for improving crops yield is the compensatory effect between seed weight (SW) and seed number (SN), which has been widely reported in several crops including Brassica napus. Despite the agronomic relevance of this issue, the molecular factors involved in the interaction between SW and SN are largely unknown in crops. In this work, we performed a detailed transcriptomic analysis of 48 seed samples obtained from two rapeseed spring genotypes subjected to different source-sink (S-S) ratios in order to modify the relationship between SW and SN under field conditions.