Project description:The gynoecium is one of the most complex organs of angiosperms specialized for seed production and dispersal, but only several genes important for ovule or embryo sac development were identified by using female sterile mutants. The female sterility in oilseed rape (Brassica napus) was before found to be related with one alien chromosome from another crucifer Orychophragmus violaceus. Herein, the developmental anatomy and comparative transcript profiling (RNA-seq) for the female sterility were performed to reveal the genes and possible metabolic pathways behind the formation of the damaged gynoecium. Using Brassica_ 95k_ unigene as the reference genome, a total of 28,065 and 27,653 unigenes were identified to be transcribed in S1 and H3, respectively, suggesting the newly initiated transcriptions in S1. Further comparison of the transcript abundance between S1 and H3 revealed that 4540 unigenes showed more than two fold expression difference. Gene ontology and pathway enrichment analysis of the Differentially Expressed Genes (DEGs) revealed that a number of important genes and metabolism pathways were involved in the development of gynoecium, embryo sac, ovule, integuments as well as the interactions between pollen and pistil. DEGs for the ovule development were detected to function in the metabolism pathways regulating brassinosteroid (BR) biosynthesis, adaxial/abaxial axis specification, auxin transport and signaling. A model was proposed to show the possible roles and interactions of these pathways for the sterile gynoecium development. The results provided new information for the molecular mechanisms behind the gynoecium development at early stage in B. napus.
Project description:Alien chromosome substitution lines are vital germplasm for breeding and genetic mapping. Previously, a whole set of nine Brassica rapa-oleracea monosonic alien addition lines (MAALs, C1-C9) was established in the background of natural B. napus genotype “Oro”, after the restituted B. rapa (RBR) for Oro was realized. Herein, a monosomic substitution line with one alien C1 chromosome (Cs1) in the RBR complement was selected in the progenies of MAAL C1 and RBR, by the PCR amplification of specific gene markers and fluorescence in situ hybridization. Cs1 exhibited the whole plant morphology similar to RBR except for the defective stamens without fertile pollen grains, but it produced some seeds and progeny plants carrying the C1 chromosome at high rate besides those without the alien chromosome after pollination by RBR. The viability of the substitution and its progeny for the restituted B. rapa diploid further elucidated the functional compensation between the chromosome pairs with high homoeology. To reveal the impact of such aneuploidy on genome-wide gene expression, the transcriptomes of MAAL C1, Cs1 and euploid RBR were analyzed. Compared to RBR, Cs1 had sharply reduced gene expression level across chromosome A1, demonstrating the loss of one copy of A1 chromosome. Both additional chromosome C1 in MAAL and substitutional chromosome C1 in Cs1 caused not only cis-effect but also prevalent trans-effect differentially expressed genes. A dominant gene dosage effects prevailed among low expressed genes across chromosome A1 in Cs1, and moreover, dosage effects for some genes potentially contributed to the phenotype deviations. Our results provided novel insights into the transcriptomic perturbation and gene dosage effects on phenotype in chromosome substitution related to one naturally evolved allopolyploid.
Project description:Background: The fertile and sterile plants are derived from the self-pollinated offspring of the F1 hybrid between novel restorer line NR1 and Nsa CMS line in Brassica napus, which possess the identical cytoplasmic genetic material arising from Nsa CMS line. As far as the nuclear genetic background is concerned, both fertile and sterile plants have the complete set of chromosomes from Brassica napus, except one or two members of the added Sinapis arvensis chromosome pair in the fertile plant. To elucidate gene expression and regulation caused by the A and C subgenomes, the alien chromosome and cytoplasm from S. arvensis during the development of young floral buds, we performed genome-widely high-throughput transcriptomic sequencing between young floral buds of sterile and fertile plants. Results: In this study, equal amount of RNA taken from young floral buds of sterile and fertile plants were sequenced using Illumina/Solexa platform. A total of 4,415,866 and 4,244,140 raw tags were obtained in sterile plant (Ste) and fertile plant (Fer) libraries, respectively. After filtering out low quality data, a total of 2,760,574 and 2,714,441 clean tags remained from the two libraries, from which 242,163 (Ste) and 253,507 (Fer) distinct tags were obtained. To identify the genes corresponding to the distinct tags in each library, all distinct sequencing tags were annotated using all possible CATG+17-nt sequences of the genome and transcriptome of Brassica rapa and those of Brassica oleracea as the reference sequences, respectively. Many genes showed substantial differences in expression between the two libraries. In total, there were 3231 genes of B. rapa and 3371 genes of B. oleracea which were detected with significant differential expression levels. GO and pathway-based analyses were performed to determine and further understand the biological functions of differentially expressed genes (DEGs). In addition, there were 1089 specially expressed unknown tags in Fer, which were neither mapped to B. oleracea nor mapped to B. rapa, and these unique tags were presumed to arise basically from the added alien chromosome of S. arvensis. Fifteen genes were randomly selected and confirmed their expression levels by quantitative RT-PCR, fourteen of the fifteen genes showed expression patterns consistent with the digital gene expression (DGE) data. Conclusions: A number of genes were differentially expressed between the young floral buds of sterile and fertile plants. Some of these genes may be candidates for future research on CMS in Nsa line, fertility restoration and improved agronomic traits in NR1 line. Further study of the unknown tags which were specially expressed in Fer will help to dig those genes with desirable agronomic traits from wild species. mRNA profiles of fertile buds (Fer) and sterile buds (Ste) were generated by deep sequencing.
Project description:Background: The fertile and sterile plants are derived from the self-pollinated offspring of the F1 hybrid between novel restorer line NR1 and Nsa CMS line in Brassica napus, which possess the identical cytoplasmic genetic material arising from Nsa CMS line. As far as the nuclear genetic background is concerned, both fertile and sterile plants have the complete set of chromosomes from Brassica napus, except one or two members of the added Sinapis arvensis chromosome pair in the fertile plant. To elucidate gene expression and regulation caused by the A and C subgenomes, the alien chromosome and cytoplasm from S. arvensis during the development of young floral buds, we performed genome-widely high-throughput transcriptomic sequencing between young floral buds of sterile and fertile plants. Results: In this study, equal amount of RNA taken from young floral buds of sterile and fertile plants were sequenced using Illumina/Solexa platform. A total of 4,415,866 and 4,244,140 raw tags were obtained in sterile plant (Ste) and fertile plant (Fer) libraries, respectively. After filtering out low quality data, a total of 2,760,574 and 2,714,441 clean tags remained from the two libraries, from which 242,163 (Ste) and 253,507 (Fer) distinct tags were obtained. To identify the genes corresponding to the distinct tags in each library, all distinct sequencing tags were annotated using all possible CATG+17-nt sequences of the genome and transcriptome of Brassica rapa and those of Brassica oleracea as the reference sequences, respectively. Many genes showed substantial differences in expression between the two libraries. In total, there were 3231 genes of B. rapa and 3371 genes of B. oleracea which were detected with significant differential expression levels. GO and pathway-based analyses were performed to determine and further understand the biological functions of differentially expressed genes (DEGs). In addition, there were 1089 specially expressed unknown tags in Fer, which were neither mapped to B. oleracea nor mapped to B. rapa, and these unique tags were presumed to arise basically from the added alien chromosome of S. arvensis. Fifteen genes were randomly selected and confirmed their expression levels by quantitative RT-PCR, fourteen of the fifteen genes showed expression patterns consistent with the digital gene expression (DGE) data. Conclusions: A number of genes were differentially expressed between the young floral buds of sterile and fertile plants. Some of these genes may be candidates for future research on CMS in Nsa line, fertility restoration and improved agronomic traits in NR1 line. Further study of the unknown tags which were specially expressed in Fer will help to dig those genes with desirable agronomic traits from wild species.
Project description:Illumina mRNA-Seq is comparable to microarray analysis for transcript quantification but has increased sensitivity and, importantly, the potential to distinguish between homoeologous genes in polyploids. Using a novel curing process, we adapted a reference sequence that was a consensus derived from ESTs from both Brassica A and C genomes to one containing A and C genome versions for each of the 94,558 original unigenes. We aligned reads from Brassica napus to this cured reference, finding 38% more reads mapping in resynthesised lines and 28% in natural lines. Where the A and C versions differed at single nucleotide positions, termed inter-homoeologue polymorphisms (IHPs), we were able to apportion expression in the polyploid to the A or C genome homoeologues. 43,761 unigenes contained at least one IHP, with a mean frequency of 10.5 per kb unigene sequence. 6,350 of the unigenes with IHPs were differentially expressed between homoeologous gene pairs in resynthesised B. napus. 3,212 unigenes showed a similar pattern of differential expression across a range of natural B. napus crop varieties and, of these, 995 were in common with resynthesised B. napus. Functional classification showed over-representation in gene ontology categories not associated with dosage-sensitivity.
Project description:The purposes of this study are to compare euploid B. napus cv. “Oro” and the C1 nullisomics transcriptome profiling (RNA-seq) and quantitative reverse transcription polymerase chain reaction (qRT–PCR) methods and to evaluate protocols for optimal high-throughput data analysis. Methods: Leaves mRNA profiles of 30-day-old euploid B. napus cv. “Oro” and the C1 nullisomics were generated by deep sequencing, in triplicate, using Illumina. The sequence reads that passed quality filters were analyzed at the transcript isoform level with two methods. qRT–PCR validation was performed. Results: After the high-throughput sequencing, each sample generated 7.2G Clean data on average and the 44.6-53.8 million clean reads were generated. Our study represents detailed analysis of leaves transcriptomes in euploid B. napus and nullisomic, with biologic replicates, generated by RNA-seq technology for comparative investigations of expression profiles. Our results show that Dose complementary effect exists between highly homologous genes, and partial loss of C subgenomic chromosome will lead to increased expression of A genome.
Project description:Aneuploidy with loss of entire chromosomes from normal complement disrupts the balanced genome and is tolerable only by polyploidy plants. In this study, the monosomic and nullisomic plants losing one or two copies of C2 chromosome from allotetraploid Brassica napus L. (2n=38, AACC) were produced and compared for their phenotype and transcriptome. The monosomics gave a plant phenotype very similar to the original donor, but the nullisomics had much smaller stature and also shorter growth period. By the comparative analyses on the global transcript profiles with the euploid donor, genome-wide alterations in gene expression were revealed in two aneuploids, and their majority of differentially expressed genes (DEGs) resulted from the trans-acting effects of the zero and one copy of C2 chromosome. The higher number of up-regulated genes than down-regulated genes on other chromosomes suggested that the genome responded to the C2 loss via enhancing the expression of certain genes. Particularly, more DEGs were detected in the monosomics than nullisomics, contrasting with their phenotypes. The gene expression of the other chromosomes was differently affected, and several dysregulated domains in which up- or downregulated genes obviously clustered were identifiable. But the mean gene expression for homoeologous chromosome A2 reduced with the C2 loss. Some genes and their expressions on C2 were correlated with the phenotype deviations in the aneuploids. These results provided new insights into the transcriptomic perturbation of the allopolyploid genome elicited by the loss of individual chromosome
Project description:mRNA expression profiling of the embryo, endosperm (micropylar, peripheral, chalazal), and seed coat (outer, inner, chalazal, chalazal proliferating tissue) of the developing Brassica napus seed. Tissues were isolated using laser microdissection (LMD) from Brassica napus seeds at the globular, heart, and mature green stages of seed development.
Project description:Aneuploidy with loss of entire chromosomes from normal complement disrupts the balanced genome and is tolerable only by polyploidy plants. In this study, the monosomic and nullisomic plants losing one or two copies of C2 chromosome from allotetraploid Brassica napus L. (2n=38, AACC) were produced and compared for their phenotype and transcriptome. The monosomics gave a plant phenotype very similar to the original donor, but the nullisomics had much smaller stature and also shorter growth period. By the comparative analyses on the global transcript profiles with the euploid donor, genome-wide alterations in gene expression were revealed in two aneuploids, and their majority of differentially expressed genes (DEGs) resulted from the trans-acting effects of the zero and one copy of C2 chromosome. The higher number of up-regulated genes than down-regulated genes on other chromosomes suggested that the genome responded to the C2 loss via enhancing the expression of certain genes. Particularly, more DEGs were detected in the monosomics than nullisomics, contrasting with their phenotypes. The gene expression of the other chromosomes was differently affected, and several dysregulated domains in which up- or downregulated genes obviously clustered were identifiable. But the mean gene expression for homoeologous chromosome A2 reduced with the C2 loss. Some genes and their expressions on C2 were correlated with the phenotype deviations in the aneuploids. These results provided new insights into the transcriptomic perturbation of the allopolyploid genome elicited by the loss of individual chromosome The newly expanded third leaves without petioles from six plants of each genotype were collected and immediately stored in liquid nitrogen for RNA extraction. Three samples with two replicates were sequenced via Illumina HiSeqTM 2000.