RESUMO
Harnessing genetic diversity in major staple crops through the development of new breeding capabilities is essential to ensure food security1. Here we examined the genetic and phenotypic diversity of the A. E. Watkins landrace collection2 of bread wheat (Triticum aestivum), a major global cereal, by whole-genome re-sequencing of 827 Watkins landraces and 208 modern cultivars and in-depth field evaluation spanning a decade. We found that modern cultivars are derived from two of the seven ancestral groups of wheat and maintain very long-range haplotype integrity. The remaining five groups represent untapped genetic sources, providing access to landrace-specific alleles and haplotypes for breeding. Linkage disequilibrium-based haplotypes and association genetics analyses link Watkins genomes to the thousands of identified high-resolution quantitative trait loci and significant marker-trait associations. Using these structured germplasm, genotyping and informatics resources, we revealed many Watkins-unique beneficial haplotypes that can confer superior traits in modern wheat. Furthermore, we assessed the phenotypic effects of 44,338 Watkins-unique haplotypes, introgressed from 143 prioritized quantitative trait loci in the context of modern cultivars, bridging the gap between landrace diversity and current breeding. This study establishes a framework for systematically utilizing genetic diversity in crop improvement to achieve sustainable food security.
Assuntos
Variação Genética , Genoma de Planta , Haplótipos , Desequilíbrio de Ligação , Fenótipo , Melhoramento Vegetal , Locos de Características Quantitativas , Triticum , Triticum/genética , Haplótipos/genética , Locos de Características Quantitativas/genética , Desequilíbrio de Ligação/genética , Variação Genética/genética , Genoma de Planta/genética , Alelos , Produtos Agrícolas/genética , Introgressão Genética , Sequenciamento Completo do GenomaRESUMO
Plants use seasonal temperature cues to time the transition to reproduction. In Arabidopsis thaliana, winter cold epigenetically silences the floral repressor locus FLOWERING LOCUS C (FLC) through POLYCOMB REPRESSIVE COMPLEX 2 (PRC2)1. This vernalization process aligns flowering with spring. A prerequisite for silencing is transcriptional downregulation of FLC, but how this occurs in the fluctuating temperature regimes of autumn is unknown2-4. Transcriptional repression correlates with decreased local levels of histone H3 trimethylation at K36 (H3K36me3) and H3 trimethylation at K4 (H3K4me3)5,6, which are deposited during FRIGIDA (FRI)-dependent activation of FLC7-10. Here we show that cold rapidly promotes the formation of FRI nuclear condensates that do not colocalize with an active FLC locus. This correlates with reduced FRI occupancy at the FLC promoter and FLC repression. Warm temperature spikes reverse this process, buffering FLC shutdown to prevent premature flowering. The accumulation of condensates in the cold is affected by specific co-transcriptional regulators and cold induction of a specific isoform of the antisense RNA COOLAIR5,11. Our work describes the dynamic partitioning of a transcriptional activator conferring plasticity in response to natural temperature fluctuations, thus enabling plants to effectively monitor seasonal progression.
Assuntos
Proteínas de Arabidopsis/genética , Arabidopsis/genética , Núcleo Celular/metabolismo , Temperatura Baixa , Regulação para Baixo , Regulação da Expressão Gênica de Plantas , Proteínas de Domínio MADS/genética , Arabidopsis/fisiologia , Núcleo Celular/genética , Flores/genética , Flores/fisiologia , Regiões Promotoras Genéticas/genética , Estabilidade Proteica , RNA Antissenso/genética , RNA de Plantas/genética , Estações do Ano , Transcrição GênicaRESUMO
Crop height (Ht), heading date (Hd), and grain yield (GY) are inter-related in wheat. Independent manipulation of each is important for adaptation and performance. Validated quantitative trait loci (QTLs) for all three co-locate on chromosome 3A in the Avalon×Cadenza population, with increased Ht, Hd, and GY contributed by Cadenza. We asked if these are linked or pleiotropic effects using recombinant lines, and showed that Ht and Hd effects are independent. The Chinese Spring equivalent to the newly defined Ht interval contained a gene cluster involved in cell wall growth and displaying high levels of differential transcript expression. The Hd locus is larger and rearranged compared with the reference genome, but FT2 (Flowering Locus T2) is of particular interest. The Hd effect acted independently of photoperiod and vernalization, but did exhibit seasonal genotype×environment interaction. Recombinants were phenotyped for GY in replicated field experiments. GY was most associated with Cadenza alleles for later Hd, supporting physiological studies using the same lines proposing that 'late' alleles at this locus increase spike fertility and grain number (GN). The work has uncoupled height from heading and yield, and shown that one of very few validated GY QTLs in wheat is probably mediated by phenological variation.
Assuntos
Locos de Características Quantitativas , Triticum , Pão , Mapeamento Cromossômico , Cromossomos , Fenótipo , Locos de Características Quantitativas/genética , Triticum/genéticaRESUMO
Variation in flowering time and response to overwintering has been exploited to breed brassica vegetables that can be harvested year-round. Our knowledge of flowering time control now enables the investigation of the molecular basis of this important variation. Here, we show that a major determinant of heading date variation in Brassica oleracea is from variation in vernalization response through allelic variation at FLOWERING LOCUS C.C2 (BoFLC4). We characterize two alleles of BoFLC.C2 that are both functional and confer a requirement for vernalization, but they show distinct expression dynamics in response to cold. Complementation experiments in Arabidopsis thaliana revealed that the allelic variation results from cis polymorphism at BoFLC.C2, which quantitatively influences the degree of cold-induced epigenetic silencing. This results in one allelic variant conferring consistently later heading under both glasshouse and field conditions through reduced environmental sensitivity. Our results suggest that breeding of brassica varieties for commercially valuable variation in heading date has been achieved through the selection of cis polymorphism at FLC, similar to that underpinning natural variation in A. thaliana. This understanding will allow for the selection of alleles with distinct sensitivities to cold and robust heading dates under variable climatic conditions, and will facilitate the breeding of varieties more resistant to climate change.
Assuntos
Brassica/genética , Flores/fisiologia , Polimorfismo Genético , Arabidopsis , Proteínas de Arabidopsis/genética , Temperatura Baixa , Regulação da Expressão Gênica de Plantas , Proteínas de Domínio MADS/genética , Proteínas de Plantas/genética , Plantas Geneticamente Modificadas , Locos de Características QuantitativasRESUMO
BACKGROUND: Plants adopt different reproductive strategies as an adaptation to growth in a range of climates. In Arabidopsis thaliana FRIGIDA (FRI) confers a vernalization requirement and thus winter annual habit by increasing the expression of the MADS box transcriptional repressor FLOWERING LOCUS C (FLC). Variation at FRI plays a major role in A. thaliana life history strategy, as independent loss-of-function alleles that result in a rapid-cycling habit in different accessions, appear to have evolved many times. The aim of this study was to identify and characterize orthologues of FRI in Brassica oleracea. RESULTS: We describe the characterization of FRI from Brassica oleracea and identify the two B. oleracea FRI orthologues (BolC.FRI.a and BolC.FRI.b). These show extensive amino acid conservation in the central and C-terminal regions to FRI from other Brassicaceae, including A. thaliana, but have a diverged N-terminus. The genes map to two of the three regions of B. oleracea chromosomes syntenic to part of A. thaliana chromosome 5 suggesting that one of the FRI copies has been lost since the ancient triplication event that formed the B. oleracea genome. This genomic position is not syntenic with FRI in A. thaliana and comparative analysis revealed a recombination event within the A. thaliana FRI promoter. This relocated A. thaliana FRI to chromosome 4, very close to the nucleolar organizer region, leaving a fragment of FRI in the syntenic location on A. thaliana chromosome 5. Our data show this rearrangement occurred after the divergence from A. lyrata. We explored the allelic variation at BolC.FRI.a within cultivated B. oleracea germplasm and identified two major alleles, which appear equally functional both to each other and A. thaliana FRI, when expressed as fusions in A. thaliana. CONCLUSIONS: We identify the two Brassica oleracea FRI genes, one of which we show through A. thaliana complementation experiments is functional, and show their genomic location is not syntenic with A. thaliana FRI due to an ancient recombination event. This has complicated previous association analyses of FRI with variation in life history strategy in the Brassica genus.
Assuntos
Alelos , Brassica/genética , Flores/crescimento & desenvolvimento , Proteínas de Plantas/genética , Sequência de Aminoácidos , Arabidopsis/genética , Arabidopsis/crescimento & desenvolvimento , Proteínas de Arabidopsis , Brassica/crescimento & desenvolvimento , Mapeamento Cromossômico , Clonagem Molecular , DNA de Plantas/genética , Flores/genética , Genoma de Planta , Genótipo , Dados de Sequência Molecular , Polimorfismo Genético , Regiões Promotoras Genéticas , Recombinação Genética , Análise de Sequência de DNA , SinteniaRESUMO
The epigenetic repression of FLOWERING LOCUS C (FLC) in winter-annual ecotypes of Arabidopsis by prolonged cold ensures that plants flower in spring and not during winter. Resetting of the FLC expression level in progeny is an important step in the life cycle of the plant. We show that both the paternally derived and the maternally derived FLC:GUS genes are reset to activity but that the timing of their first expression differs. The paternal FLC:GUS gene in vernalized plants is expressed in the male reproductive organs, the anthers, in both somatic tissue and in the sporogenous pollen mother cells, but there is no expression in mature pollen. In the progeny generation, the paternally derived FLC:GUS gene is expressed in the single-celled zygote (fertilized egg cell) and through embryo development, but not in the fertilized central cell, which generates the endosperm of the progeny seed. FLC:GUS is not expressed during female gametogenesis, with the maternally derived FLC:GUS being first expressed in the early multicellular embryo. We show that FLC activity during late embryo development is a prerequisite for the repressive action of FLC on flowering.
Assuntos
Proteínas de Arabidopsis/genética , Arabidopsis/genética , Epigênese Genética , Regulação da Expressão Gênica de Plantas , Proteínas de Domínio MADS/genética , Arabidopsis/embriologia , Sementes/crescimento & desenvolvimentoRESUMO
The epigenetic regulation of the floral repressor Flowering Locus C (FLC) is one of the critical factors that determine flowering time in Arabidopsis thaliana. Although many FLC regulators, and their effects on FLC chromatin, have been extensively studied, the epigenetic resetting of FLC has not yet been thoroughly characterized. Here, we investigate the FLC expression during gametogenesis and embryogenesis using FLC::GUS transgenic plants and RNA analysis. Regardless of the epigenetic state in adult plants, FLC expression disappeared in gametophytes. Subsequently, FLC expression was reactivated after fertilization in embryos, but not in the endosperm. Both parental alleles contributed equally to the expression of FLC in embryos. Surprisingly, the reactivation of FLC in early embryos was independent of FRIGIDA (FRI) and SUPPRESSOR OF FRIGIDA 4 (SUF4) activities. Instead, FRI, SUF4 and autonomous-pathway genes determined the level of FLC expression only in late embryogenesis. Many FLC regulators exhibited expression patterns similar to that of FLC, indicating potential roles in FLC reprogramming. An FVE mutation caused ectopic expression of FLC in the endosperm. A mutation in PHOTOPERIOD-INDEPENDENT EARLY FLOWERING 1 caused defects in FLC reactivation in early embryogenesis, and maintenance of full FLC expression in late embryogenesis. We also show that the polycomb group complex components, Fertilization-Independent endosperm and MEDEA, which mediate epigenetic regulation in seeds, are not relevant for FLC reprogramming. Based on our results, we propose that FLC reprogramming is composed of three phases: (i) repression in gametogenesis, (ii) reactivation in early embryogenesis and (iii) maintenance in late embryogenesis.
Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/genética , Epigênese Genética , Proteínas de Domínio MADS/metabolismo , Alelos , Arabidopsis/embriologia , Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Cruzamentos Genéticos , Perfilação da Expressão Gênica , Regulação da Expressão Gênica no Desenvolvimento , Regulação da Expressão Gênica de Plantas , Proteínas de Domínio MADS/genética , Plantas Geneticamente Modificadas/genética , Plantas Geneticamente Modificadas/crescimento & desenvolvimento , Plantas Geneticamente Modificadas/metabolismo , RNA de Plantas/metabolismoRESUMO
To ensure flowering in favourable conditions, many plants flower only after an extended period of cold, namely winter. In Arabidopsis, the acceleration of flowering by prolonged cold, a process called vernalization, involves downregulation of the protein FLC, which would otherwise prevent flowering. This lowered FLC expression is maintained through subsequent development by the activity of VERNALIZATION (VRN) genes. VRN1 encodes a DNA-binding protein whereas VRN2 encodes a homologue of one of the Polycomb group proteins, which maintain the silencing of genes during animal development. Here we show that vernalization causes changes in histone methylation in discrete domains within the FLC locus, increasing dimethylation of lysines 9 and 27 on histone H3. Such modifications identify silenced chromatin states in Drosophila and human cells. Dimethylation of H3 K27 was lost only in vrn2 mutants, but dimethylation of H3 K9 was absent from both vrn1 and vrn2, consistent with VRN1 functioning downstream of VRN2. The epigenetic memory of winter is thus mediated by a 'histone code' that specifies a silent chromatin state conserved between animals and plants.
Assuntos
Proteínas de Arabidopsis/genética , Arabidopsis/crescimento & desenvolvimento , Arabidopsis/genética , Flores/crescimento & desenvolvimento , Regulação da Expressão Gênica de Plantas , Inativação Gênica , Histonas/metabolismo , Proteínas de Domínio MADS/genética , Proteínas Repressoras , Proteínas de Arabidopsis/metabolismo , Proteínas de Transporte/química , Proteínas de Transporte/genética , Proteínas de Transporte/metabolismo , Cromatina/genética , Cromatina/metabolismo , Montagem e Desmontagem da Cromatina , Temperatura Baixa , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Flores/genética , Genes de Plantas/genética , Metilação , Mutação/genética , Proteínas Nucleares/química , Proteínas Nucleares/genética , Proteínas Nucleares/metabolismo , Estações do Ano , Dedos de ZincoRESUMO
A potentially serious disadvantage of association mapping is the fact that marker-trait associations may arise from confounding population structure as well as from linkage to causative polymorphisms. Using genome-wide marker data, we have previously demonstrated that the problem can be severe in a global sample of 95 Arabidopsis thaliana accessions, and that established methods for controlling for population structure are generally insufficient. Here, we use the same sample together with a number of flowering-related phenotypes and data-perturbation simulations to evaluate a wider range of methods for controlling for population structure. We find that, in terms of reducing the false-positive rate while maintaining statistical power, a recently introduced mixed-model approach that takes genome-wide differences in relatedness into account via estimated pairwise kinship coefficients generally performs best. By combining the association results with results from linkage mapping in F2 crosses, we identify one previously known true positive and several promising new associations, but also demonstrate the existence of both false positives and false negatives. Our results illustrate the potential of genome-wide association scans as a tool for dissecting the genetics of natural variation, while at the same time highlighting the pitfalls. The importance of study design is clear; our study is severely under-powered both in terms of sample size and marker density. Our results also provide a striking demonstration of confounding by population structure. While statistical methods can be used to ameliorate this problem, they cannot always be effective and are certainly not a substitute for independent evidence, such as that obtained via crosses or transgenic experiments. Ultimately, association mapping is a powerful tool for identifying a list of candidates that is short enough to permit further genetic study.
Assuntos
Arabidopsis/genética , Mapeamento Cromossômico , Fatores de Confusão Epidemiológicos , Genoma de Planta/genética , Haplótipos , Modelos Lineares , Modelos Genéticos , Fenótipo , Polimorfismo de Nucleotídeo Único , Dinâmica Populacional , Análise de Componente PrincipalRESUMO
The detection of footprints of natural selection in genetic polymorphism data is fundamental to understanding the genetic basis of adaptation, and has important implications for human health. The standard approach has been to reject neutrality in favor of selection if the pattern of variation at a candidate locus was significantly different from the predictions of the standard neutral model. The problem is that the standard neutral model assumes more than just neutrality, and it is almost always possible to explain the data using an alternative neutral model with more complex demography. Today's wealth of genomic polymorphism data, however, makes it possible to dispense with models altogether by simply comparing the pattern observed at a candidate locus to the genomic pattern, and rejecting neutrality if the pattern is extreme. Here, we utilize this approach on a truly genomic scale, comparing a candidate locus to thousands of alleles throughout the Arabidopsis thaliana genome. We demonstrate that selection has acted to increase the frequency of early-flowering alleles at the vernalization requirement locus FRIGIDA. Selection seems to have occurred during the last several thousand years, possibly in response to the spread of agriculture. We introduce a novel test statistic based on haplotype sharing that embraces the problem of population structure, and so should be widely applicable.
Assuntos
Arabidopsis/genética , Arabidopsis/fisiologia , Flores/fisiologia , Alelos , Proteínas de Arabidopsis/genética , Evolução Biológica , Flores/genética , Genoma de Planta , Polimorfismo Genético , Dinâmica Populacional , Seleção Genética , Estatísticas não Paramétricas , Fatores de TempoRESUMO
There is currently tremendous interest in the possibility of using genome-wide association mapping to identify genes responsible for natural variation, particularly for human disease susceptibility. The model plant Arabidopsis thaliana is in many ways an ideal candidate for such studies, because it is a highly selfing hermaphrodite. As a result, the species largely exists as a collection of naturally occurring inbred lines, or accessions, which can be genotyped once and phenotyped repeatedly. Furthermore, linkage disequilibrium in such a species will be much more extensive than in a comparable outcrossing species. We tested the feasibility of genome-wide association mapping in A. thaliana by searching for associations with flowering time and pathogen resistance in a sample of 95 accessions for which genome-wide polymorphism data were available. In spite of an extremely high rate of false positives due to population structure, we were able to identify known major genes for all phenotypes tested, thus demonstrating the potential of genome-wide association mapping in A. thaliana and other species with similar patterns of variation. The rate of false positives differed strongly between traits, with more clinal traits showing the highest rate. However, the false positive rates were always substantial regardless of the trait, highlighting the necessity of an appropriate genomic control in association studies.
Assuntos
Arabidopsis/genética , Predisposição Genética para Doença , Genoma de Planta , Imunidade Inata , Mapeamento Cromossômico , Reações Falso-Positivas , Genes de Plantas , Variação Genética , Genótipo , Desequilíbrio de LigaçãoRESUMO
Aims and method To ascertain differences in patterns of suicide in young men over three decades (1960s, 1990s and 2000s) and discuss implications for suicide prevention. Data on suicides and open verdicts in men aged 15-34 were obtained from coroner's records in Newcastle upon Tyne and analysed using SPSS software. Results An increase in suicide rates from the first to the second decade was followed by a fall in the third decade. This was associated with an increasing proportion of single men, those living alone, unemployment, consumption of alcohol, use of hanging, previous suicide attempt and history of treatment for mental illness. Clinical implications This study highlights the need for more interventions and focus to be given to young males in the suicide prevention area and is of high importance in the field of public health. Areas that could be tackled include reducing access to means of suicide, reducing alcohol use, support for relationship difficulties, engagement with mental health services and management of chronic illness.
RESUMO
Arabidopsis thaliana accessions have adapted to growth in a wide range of climates. Variation in flowering and alignment of vernalization response with winter length are central to this adaptation. Vernalization involves the epigenetic silencing of the floral repressor FLC via a conserved Polycomb (PRC2) mechanism involving trimethylation of Lys(27) on histone H3 (H3K27me3). We found that variation for response to winter length maps to cis polymorphism within FLC. A rare combination of four polymorphisms localized around the nucleation region of a PHD-Polycomb complex determines a need for longer cold. Chromatin immunoprecipitation experiments indicate that these polymorphisms influence the accumulation of H3K27me3 in Arabidopsis accession Lov-1, both at the nucleation site and over the gene body. Quantitative modulation of chromatin silencing through cis variation may be a general mechanism contributing to evolutionary change.
Assuntos
Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Arabidopsis/genética , Temperatura Baixa , Flores/genética , Regulação da Expressão Gênica de Plantas , Inativação Gênica , Proteínas de Domínio MADS/genética , Proteínas Repressoras/metabolismo , Arabidopsis/crescimento & desenvolvimento , Cromatina/genética , Cromatina/metabolismo , Imunoprecipitação da Cromatina , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Elementos Facilitadores Genéticos , Flores/crescimento & desenvolvimento , Histonas/genética , Histonas/metabolismo , Lisina/genética , Lisina/metabolismo , Metilação , Complexo Repressor Polycomb 2 , Proteínas do Grupo Polycomb , Polimorfismo Genético , Proteínas Repressoras/genética , Estações do AnoRESUMO
We have explored the genetic basis of variation in vernalization requirement and response in Arabidopsis accessions, selected on the basis of their phenotypic distinctiveness. Phenotyping of F2 populations in different environments, plus fine mapping, indicated possible causative genes. Our data support the identification of FRI and FLC as candidates for the major-effect QTL underlying variation in vernalization response, and identify a weak FLC allele, caused by a Mutator-like transposon, contributing to flowering time variation in two N. American accessions. They also reveal a number of additional QTL that contribute to flowering time variation after saturating vernalization. One of these was the result of expression variation at the FT locus. Overall, our data suggest that distinct phenotypic variation in the vernalization and flowering response of Arabidopsis accessions is accounted for by variation that has arisen independently at relatively few major-effect loci.
Assuntos
Proteínas de Arabidopsis/genética , Arabidopsis/genética , Temperatura Baixa , Flores/fisiologia , Variação Genética , Proteínas de Domínio MADS/genética , Locos de Características Quantitativas , Alelos , Arabidopsis/crescimento & desenvolvimento , Regulação da Expressão Gênica de Plantas , Fenótipo , RNA Mensageiro/genética , Reação em Cadeia da Polimerase Via Transcriptase ReversaRESUMO
Noncoding RNA is emerging as an important regulator of gene expression in many organisms. We are characterizing RNA-mediated chromatin silencing of the Arabidopsis major floral repressor gene, FLC. Through suppressor mutagenesis, we identify a requirement for CstF64 and CstF77, two conserved RNA 3'-end-processing factors, in FLC silencing. However, FLC sense transcript 3' processing is not affected in the mutants. Instead, CstF64 and CstF77 are required for 3' processing of FLC antisense transcripts. A specific RNA-binding protein directs their activity to a proximal antisense polyadenylation site. This targeted processing triggers localized histone demethylase activity and results in reduced FLC sense transcription. Targeted 3' processing of antisense transcripts may be a common mechanism triggering transcriptional silencing of the corresponding sense gene.
Assuntos
Proteínas de Arabidopsis/genética , Arabidopsis/genética , Cromatina/genética , Regulação da Expressão Gênica de Plantas , Inativação Gênica , Proteínas de Domínio MADS/genética , RNA Antissenso/metabolismo , RNA de Plantas/metabolismo , Arabidopsis/crescimento & desenvolvimento , Arabidopsis/metabolismo , Proteínas de Arabidopsis/metabolismo , Cromatina/metabolismo , Fator Estimulador de Clivagem/genética , Fator Estimulador de Clivagem/metabolismo , Epistasia Genética , Flores/crescimento & desenvolvimento , Histona Desacetilases/genética , Histona Desacetilases/metabolismo , Proteínas de Domínio MADS/metabolismo , Modelos Genéticos , Poliadenilação , Processamento Pós-Transcricional do RNA , Proteínas de Ligação a RNA/genética , Proteínas de Ligação a RNA/metabolismo , Supressão Genética , Transcrição Gênica , Fatores de Poliadenilação e Clivagem de mRNA/genética , Fatores de Poliadenilação e Clivagem de mRNA/metabolismoRESUMO
Vernalization, the cold-induced acceleration of flowering, involves the epigenetic silencing of the floral repressor gene FLOWERING LOCUS C (FLC). We investigated the molecular basis for variation in vernalization in Arabidopsis natural accessions adapted to different climates. A major variable was the degree to which different periods of cold caused stable FLC silencing. In accessions requiring long vernalization, FLC expression was reactivated following nonsaturating vernalization, but this reactivation was progressively attenuated with increasing cold exposure. This response was correlated with the rate of accumulation of FLC histone H3 Lys 27 trimethylation (H3K27me3). Thus, variation in epigenetic silencing of FLC appears to have contributed to Arabidopsis adaptation.
Assuntos
Proteínas de Arabidopsis/genética , Arabidopsis/fisiologia , Temperatura Baixa , Epigênese Genética , Flores/fisiologia , Inativação Gênica , Variação Genética , Proteínas de Domínio MADS/genética , Alelos , Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Cromatina/metabolismo , Imunoprecipitação da Cromatina , Regulação da Expressão Gênica de Plantas , Genes de Plantas , Proteínas de Domínio MADS/metabolismo , Modelos Genéticos , Fenótipo , Locos de Características Quantitativas/genética , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Proteínas Repressoras/metabolismoRESUMO
Arabidopsis (Arabidopsis thaliana) accessions provide an excellent resource to dissect the molecular basis of adaptation. We have selected 192 Arabidopsis accessions collected to represent worldwide and local variation and analyzed two adaptively important traits, flowering time and vernalization response. There was huge variation in the flowering habit of the different accessions, with no simple relationship to latitude of collection site and considerable diversity occurring within local regions. We explored the contribution to this variation from the two genes FRIGIDA (FRI) and FLOWERING LOCUS C (FLC), previously shown to be important determinants in natural variation of flowering time. A correlation of FLC expression with flowering time and vernalization was observed, but it was not as strong as anticipated due to many late-flowering/vernalization-requiring accessions being associated with low FLC expression and early-flowering accessions with high FLC expression. Sequence analysis of FRI revealed which accessions were likely to carry functional alleles, and, from comparison of flowering time with allelic type, we estimate that approximately 70% of flowering time variation can be accounted for by allelic variation of FRI. The maintenance and propagation of 20 independent nonfunctional FRI haplotypes suggest that the loss-of-function mutations can confer a strong selective advantage. Accessions with a common FRI haplotype were, in some cases, associated with very different FLC levels and wide variation in flowering time, suggesting additional variation at FLC itself or other genes regulating FLC. These data reveal how useful these Arabidopsis accessions will be in dissecting the complex molecular variation that has led to the adaptive phenotypic variation in flowering time.
Assuntos
Proteínas de Arabidopsis/fisiologia , Arabidopsis/genética , Arabidopsis/fisiologia , Flores/fisiologia , Proteínas de Domínio MADS/fisiologia , Sequência de Aminoácidos , Proteínas de Arabidopsis/genética , Variação Genética , Proteínas de Domínio MADS/genética , Dados de Sequência Molecular , Polimorfismo Genético , RNA Mensageiro , RNA de PlantasRESUMO
A report on the seventh meeting of the International Society for Plant Molecular Biology (ISPMB), Barcelona, Spain, 23-28 June 2003.