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Seedling development traits in Brassica napus examined by gene expression analysis and association mapping.

ABSTRACT: An optimal seedling development of Brassica napus plants leads to a higher yield stability even under suboptimal growing conditions and has therefore a high importance for plant breeders. The objectives of our study were to (i) examine the expression levels of candidate genes in seedling leaves of B. napus and correlate these with seedling development as well as (ii) detect genome regions associated with gene expression levels and seedling development traits in B. napus by genome-wide association mapping.The expression levels of the 15 candidate genes examined in the 509 B. napus inbreds showed an averaged standard deviation of 5.6 across all inbreds and ranged from 3.2 to 8.8. The gene expression differences between the 509 B. napus inbreds were more than adequate for the correlation with phenotypic variation of seedling development. The average of the absolute value correlations of the correlation coefficients of 0.11 were observed with a range from 0.00 to 0.39. The candidate genes GER1, AILP1, PECT, and FBP were strongly correlated with the seedling development traits. In a genome-wide association study, we detected a total of 63 associations between single nucleotide polymorphisms (SNPs) and the seedling development traits and 31 SNP-gene associations for the candidate genes with a P-value < 0.0001. For the projected leaf area traits we identified five different association hot spots on the chromosomes A2, A7, C3, C6, and C7.A total of 99.4% of the adjacent SNPs on the A genome and 93.0% of the adjacent SNPs on the C genome had a distance smaller than the average range of linkage disequilibrium. Therefore, this genome-wide association study is expected to result on average in 14.7% of the possible power. Compared to previous studies in B. napus, the SNP marker density of our study is expected to provide a higher power to detect SNP-trait/-gene associations in the B. napus diversity set. The large number of associations detected for the examined 14 seedling development traits indicated that these are genetically complex inherited. The results of our analyses suggested that the studied genes ribulose 1,5-bisphosphate carboxylase/oxygenase small subunit (RBC) on the chromosomes A4 and C4 and fructose-1,6-bisphosphatase precursor (FBP) on the chromosomes A9 and C8 are cis-regulated.

SUBMITTER: Korber N

PROVIDER: S-EPMC4459455 | biostudies-literature | 2015 Jun

REPOSITORIES: biostudies-literature

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Seedling development traits in Brassica napus examined by gene expression analysis and association mapping.

Körber Niklas N Bus Anja A Li Jinquan J Higgins Janet J Bancroft Ian I Higgins Erin Eileen EE Parkin Isobel Alison Papworth IA Salazar-Colqui Bertha B Snowdon Rod John RJ Stich Benjamin B

BMC plant biology 20150609

<h4>Background</h4>An optimal seedling development of Brassica napus plants leads to a higher yield stability even under suboptimal growing conditions and has therefore a high importance for plant breeders. The objectives of our study were to (i) examine the expression levels of candidate genes in seedling leaves of B. napus and correlate these with seedling development as well as (ii) detect genome regions associated with gene expression levels and seedling development traits in B. napus by gen ...[more]

PMID: 26055390

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Project description:Distant hybridization usually leads to female sterility of the hybrid but the mechanism behind this is poorly understood. Complete pistil abortion but normal male fertility was shown by one Brassica napus-Orychophragmus violaceus monosomic alien addition line (MA, AACC + 1 IO, 2n = 39) produced previously. To study the effect of a single O. violaceus chromosome addition on pistil development in different genetic backgrounds, hybrids between the MA and B. carinata (BBCC), B. juncea (AABB), and two synthetic hexaploids (AABBCC) were firstly produced in this study which show complete female sterility. A microspore culture was further performed to produce the haploid monosomic alien addition line (HMA, AC + 1 IO, 2n = 20) and disomic addition line (DA, AACC + 2 IO, 2n = 40) together with haploid (H, AC, 2n = 19) and double haploid (DH, AACC, 2n = 38) plants of B. napus from MA to investigate the dosage effect of the alien O. violaceus chromosome on pistil development and gene expression. Compared to MA, the development of the pistils of DA and HMA was completely or partially recovered, in which the pistils could swell and elongate to a normal shape after open pollination, although no seeds were produced. Comparative RNA-seq analyses revealed that the numbers of the differentially expressed genes (DEGs) were significantly different, dosage-dependent, and consistent with the phenotypic difference in pairwise comparisons of HMA vs. H, DA vs. DH, MA vs. DH, MA vs. DA, and MA vs. HMA. The gene ontology (GO) enrichment analysis of DEGs showed that a number of genes involved in the development of the gynoecium, embryo sac, ovule, and integuments. Particularly, several common DEGs for pistil development shared in HMA vs. H and DA vs. DH showed functions in genotoxic stress response, auxin transport, and signaling and adaxial/abaxial axis specification. The results provided updated information for the molecular mechanisms behind the gynoecium development of B. napus responding to the dosage of alien O. violaceus chromosomes.

Project description:The Brassica napus (oilseed rape) accession 1012-98 shows a disturbed germination phenotype that was thought to be associated with its lack of testa pigmentation and thin seed coat. Here, we demonstrate that the disturbed germination and seedling development are actually due to independent mutations that disrupt the balance of hormone metabolites and their regulators in the seeds. High-throughput UPLC-MS/MS hormone profiling of seeds and seedlings before and after germination revealed that 1012-98 has a severely disturbed hormone balance with extremely atypical, excessive quantities of auxin and ABA metabolites. The resulting hypersensitivity to abscisic acid (ABA) and a corresponding increase in dormancy often results in death of the embryo after imbibition or high frequencies of disturbed, often lethal developmental phenotypes, resembling Arabidopsis mutants for the auxin regulatory factor gene ARF10 or the auxin-overproducing transgenic line iaaM-OX. Molecular cloning of Brassica ARF10 orthologs revealed four loci in normal B. napus, two derived from the Brassica A genome and two from the C genome. On the other hand, the phenotypic mutant 1012-98 exhibited amplification of C-genome BnaC.ARF10 copy number along with a chimeric allele originating from recombination between homeologous A and C genome loci which lead to minor increase of Bna.ARF10 transcription on the critical timepoint for seed germination, the indirect regulator of ABI3, the germinative inhibitor. Bna.GH3.5 expression was upregulated to conjugate free auxin to IAA-asp between 2 and 6 DAS. Functional amino acid changes were also found in important DNA binding domains of one BnaC.ARF10 locus, suggesting that regulatory changes in Bna.ARF10 are collectively responsible for the observed phenotpyes in 1012-98. To our knowledge, this study is the first to report disruption of germination and seedling development in Brassica napus caused by the crosstalk of auxin-ABA and the corresponding regulators Bna.ARF10 and Bna.GH3.5.

Dataset Information

Seedling development traits in Brassica napus examined by gene expression analysis and association mapping.

Publications

Seedling development traits in Brassica napus examined by gene expression analysis and association mapping.

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