Project description:Plant architecture is central to yield and has been at the core of crop domestication and improvement. In cereals, inflorescence branching and leaf angle are important traits that contribute to planting density and yield potential. Several classical maize mutants show disruptions in both traits, suggesting a core regulatory network underlies pleiotropy between them. Here, we investigate regulatory modules that contribute to architectural pleiotropy between tassel branch number (TBN) and leaf angle (LA) in maize by defining transcriptional networks that function in lateral organ boundaries to promote development of these morphologically distinct organs. Using a set of nine mutants with specific developmental defects in one or both traits, we generated dynamic, context-specific gene regulatory maps that describe ligule and tassel branch development at the molecular level. Mutants introgressed into B73 and control plants were grown in environmentally controlled chambers and precisely-staged tassel primordia were hand-dissected at two stages: right before and after first primary branches initiated. Two stages capturing early development of the ligular region, including the shoot apical meristem, were also collected from mutants with LA defects. RNA-seq was performed on 140 samples and integrated into gene regulatory and co-expression networks, which were extended to include publicly available transcription factor occupancy maps for important developmental regulators, chromatin accessibility maps and natural variation to help prioritize novel genes and regulatory elements underlying diversity in LA and tassel branching phenotypes. We also used these transcriptional networks to guide multi-trait genome-wide association studies (GWAS) based on three years of field phenotyping TBN and LA traits in over 500 diverse maize lines. Various network-assisted GWAS approaches were used to identify polymorphisms in candidate genes that associate with these architecture traits and the pleiotropy between them. Our data provide novel insight into regulatory mechanisms controlling architectural pleiotropy that can be used for targeted crop improvement.

Project description:The data set submitted here contains the raw SNP genotyping data obtained from the analysis of 24 biparental segregating maize (Zea mays L.) populations and their respective parents. The processed and filtered data were used to construct genetic linkage maps which we used in our study of variation of recombination rate in maize. In sexually reproducing organisms, meiotic crossovers ensure the proper segregation of chromosomes and contribute to genetic diversity by shuffling allelic combinations. Such genetic reassortment is exploited in breeding to combine favorable alleles, and in genetic research to identify genetic factors underlying traits of interest via linkage or association-based approaches. Crossover numbers and distributions along chromosomes vary between species, but little is known about their intraspecies variation. In our study, we report on the variation of recombination rates between 22 European maize inbred lines that belong to the Dent and Flint gene pools. We genotyped 23 doubled-haploid populations derived from crosses between these lines with a 50k-SNP array and constructed high-density genetic maps, showing good correspondence with the maize B73 genome sequence assembly. By aligning each genetic map to the B73 sequence, we obtained the recombination rates along chromosomes specific to each population. We identified significant differences in recombination rates at the genome-wide, chromosome, and intrachromosomal levels between populations, as well as significant variation for genome-wide recombination rates among maize lines. Crossover interference analysis using a two-pathway modeling framework revealed a negative association between recombination rate and interference strength. To our knowledge, the present work provides the most comprehensive study on intraspecific variation of recombination rates and crossover interference strength in eukaryotes. Differences found in recombination rates will allow for selection of high or low recombining lines in crossing programs. Our methodology should pave the way for precise identification of genes controlling recombination rates in maize and other organisms.

Project description:The data set submitted here contains the raw SNP genotyping data obtained from the analysis of 24 biparental segregating maize (Zea mays L.) populations and their respective parents. The processed and filtered data were used to construct genetic linkage maps which we used in our study of variation of recombination rate in maize. In sexually reproducing organisms, meiotic crossovers ensure the proper segregation of chromosomes and contribute to genetic diversity by shuffling allelic combinations. Such genetic reassortment is exploited in breeding to combine favorable alleles, and in genetic research to identify genetic factors underlying traits of interest via linkage or association-based approaches. Crossover numbers and distributions along chromosomes vary between species, but little is known about their intraspecies variation. In our study, we report on the variation of recombination rates between 22 European maize inbred lines that belong to the Dent and Flint gene pools. We genotyped 23 doubled-haploid populations derived from crosses between these lines with a 50k-SNP array and constructed high-density genetic maps, showing good correspondence with the maize B73 genome sequence assembly. By aligning each genetic map to the B73 sequence, we obtained the recombination rates along chromosomes specific to each population. We identified significant differences in recombination rates at the genome-wide, chromosome, and intrachromosomal levels between populations, as well as significant variation for genome-wide recombination rates among maize lines. Crossover interference analysis using a two-pathway modeling framework revealed a negative association between recombination rate and interference strength. To our knowledge, the present work provides the most comprehensive study on intraspecific variation of recombination rates and crossover interference strength in eukaryotes. Differences found in recombination rates will allow for selection of high or low recombining lines in crossing programs. Our methodology should pave the way for precise identification of genes controlling recombination rates in maize and other organisms. Related publication: Bauer E, Falque M, Walter H, Bauland C, Camisan C, Campo L, Meyer N, Ranc N, Rincent R, Schipprack W, Altmann T, Flament P, Melchinger AE, Menz M, Moreno-González J, Ouzunova M, Revilla P, Charcosset A, Martin OC, Schön C-C (2013) Intraspecific variation of recombination rate in maize. Genome Biology (submitted) We genotyped 2233 maize DH lines from 24 biparental populations, and the 23 parents of these populations using the Illumina MaizeSNP50 BeadChip. We created two large half-sib panels, one each for the Dent and the Flint germplasm. The Dent populations have the prefix CFD, the Flint populations have the prefix CFF. In each panel, a common central parent was crossed to diverse founder lines, and doubled haploids were generated from the respective F1 plants. For a detailed description of the material, see Bauer et al. (2013) Genome Biology (submitted). We submit here three datasets: 1) Dataset Parents comprises all 23 parental lines. 2) Dataset CFD comprises all 1005 DH lines from Dent crosses, 3) Dataset CFF comprises all 1262 DH lines from Flint crosses.

Project description:Different individuals of the same species are generally thought to have very similar genomes. However, there is growing evidence that structural variation in the form of copy number variation (CNV) and presence-absence variation (PAV) can lead to variation in the genome content of individuals within a species. In order to investigate the potential contribution of CNV and PAV to genomic diversity in maize we used array comparative genomic hybridization (CGH) to compare gene content and copy number variation among 25 diverse maize inbreds 14 genotypes of the wild ancestor of maize, teosinte. The microarray included multiple probes for each of the ~32,500 stringently filtered genes identified in the B73 reference genome. We identified 479 genes exhibiting higher copy number in some genotypes (UpCNV) and 3,410 genes that have either fewer copies or are missing in the genome of at least one genotype relative to B73 (DownCNV/PAV). Many of these DownCNV/PAV are examples of genes that are present in B73 but missing from the genome of several other genotypes. Over 70% of the CNV/PAV examples are identified in multiple genotypes and the majority of events are observed in both maize and teosinte suggesting that these reflect relatively old variants that are not associated with domestication or maize improvement. Many of the genes affected by CNV/PAV are either maize-specific or members of genes families suggesting that the gene loss can be tolerated through buffering by redundant functions encoded elsewhere in the genome. Many plant genomes are relatively large and contain the remnant of whole genome duplications which may provide the ability to tolerate high levels of structural variation. While this structural variation may not result in major qualitative variation due to genetic buffering, it may significantly contribute to quantitative variation. 1-2 replications of 25 maize inbred and 14 teosinte genotypes were hybridized to an array designed from the ~32,400 genes in the maize B73 reference genome.

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Regulatory variation controlling architectural pleiotropy in maize

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