Dataset Information

Evolutionary conservation of the FLOWERING LOCUS C-mediated vernalization response: evidence from the sugar beet (Beta vulgaris).

ABSTRACT: In many plant species, exposure to a prolonged period of cold during the winter promotes flowering in the spring, a process termed vernalization. In Arabidopsis thaliana, the vernalization requirement of winter-annual ecotypes is caused by the MADS-box gene FLOWERING LOCUS C (FLC), which is a repressor of flowering. During the vernalization process, FLC is downregulated by alteration of its chromatin structure, thereby permitting flowering to occur. In wheat, a vernalization requirement is imposed by a different repressor of flowering, suggesting that some components of the regulatory network controlling the vernalization response differ between monocots and dicots. The extent to which the molecular mechanisms underlying vernalization have been conserved during the diversification of the angiosperms is not well understood. Using phylogenetic analysis, we identified homologs of FLC in species representing the three major eudicot lineages. FLC homologs have not previously been documented outside the plant family Brassicaceae. We show that the sugar beet FLC homolog BvFL1 functions as a repressor of flowering in transgenic Arabidopsis and is downregulated in response to cold in sugar beet. Cold-induced downregulation of an FLC-like floral repressor may be a central feature of the vernalization response in at least half of eudicot species.

SUBMITTER: Reeves PA

PROVIDER: S-EPMC1893026 | biostudies-literature | 2007 May

REPOSITORIES: biostudies-literature

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Evolutionary conservation of the FLOWERING LOCUS C-mediated vernalization response: evidence from the sugar beet (Beta vulgaris).

Reeves Patrick A PA He Yuehui Y Schmitz Robert J RJ Amasino Richard M RM Panella Lee W LW Richards Christopher M CM

Genetics 20061218 1

In many plant species, exposure to a prolonged period of cold during the winter promotes flowering in the spring, a process termed vernalization. In Arabidopsis thaliana, the vernalization requirement of winter-annual ecotypes is caused by the MADS-box gene FLOWERING LOCUS C (FLC), which is a repressor of flowering. During the vernalization process, FLC is downregulated by alteration of its chromatin structure, thereby permitting flowering to occur. In wheat, a vernalization requirement is impos ...[more]

PMID: 17179080

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Project description:BackgroundCytoplasmic male sterility (CMS) is a widely used trait for hybrid seed production in many crops. Sugar beet CMS is associated with a unique mitochondrial protein named preSATP6 that forms a 250-kDa complex. Restorer-of-fertility 1 (Rf1) is a nuclear gene that suppresses CMS and is, hence, one of the targets of sugar beet breeding. Rf1 has dominant, semi-dominant and recessive alleles, suggesting that it may be a multi-allelic locus; however, the molecular basis for differences in genetic action is obscure. Molecular cloning of Rf1 revealed a gene (orf20) whose protein products produced in transgenics can bind with preSATP6 to generate a novel 200-kDa complex. The complex is also detected in fertility-restored anthers concomitant with a decrease in the amount of the 250-kDa complex. Molecular diversity of the Rf1 locus involves organizational diversity of a gene cluster composed of orf20-like genes (RF-Oma1s). We examined the possibility that members of the clustered RF-Oma1 in this locus could be associated with fertility restoration.ResultsSix yet uncharacterized RF-Oma1s from dominant and recessive alleles were examined to determine whether they could generate the 200-kDa complex. Analyses of transgenic calli revealed that three RF-Oma1s from a dominant allele could generate the 200-kDa complex, suggesting that clustered RF-Oma1s in the dominant allele can participate in fertility restoration. None of the three copies from two recessive alleles was 200-kDa generative. The absence of this ability was confirmed by analyzing mitochondrial complexes in anthers of plants having these recessive alleles. Together with our previous data, we designed a set of PCR primers specific to the 200-kDa generative RF-Oma1s. The amount of mRNA measured by this primer set inversely correlated with the amount of the 250-kDa complex in anthers and positively correlated with the strength of the Rf1 alleles.ConclusionsFertility restoration by sugar beet Rf1 can involve multiple RF-Oma1s clustered in the locus, implying that stacking 200-kDa generative copies in the locus strengthens the efficacy, whereas the absence of 200-kDa generative copies in the locus makes the allele recessive irrespective of the copy number. We propose that sugar beet Rf1 is a complex locus.

Project description:Third generation sequencing methods, like SMRT (Single Molecule, Real-Time) sequencing developed by Pacific Biosciences, offer much longer read length in comparison to Next Generation Sequencing (NGS) methods. Hence, they are well suited for de novo- or re-sequencing projects. Sequences generated for these purposes will not only contain reads originating from the nuclear genome, but also a significant amount of reads originating from the organelles of the target organism. These reads are usually discarded but they can also be used for an assembly of organellar replicons. The long read length supports resolution of repetitive regions and repeats within the organelles genome which might be problematic when just using short read data. Additionally, SMRT sequencing is less influenced by GC rich areas and by long stretches of the same base.We describe a workflow for a de novo assembly of the sugar beet (Beta vulgaris ssp. vulgaris) chloroplast genome sequence only based on data originating from a SMRT sequencing dataset targeted on its nuclear genome. We show that the data obtained from such an experiment are sufficient to create a high quality assembly with a higher reliability than assemblies derived from e.g. Illumina reads only. The chloroplast genome is especially challenging for de novo assembling as it contains two large inverted repeat (IR) regions. We also describe some limitations that still apply even though long reads are used for the assembly.SMRT sequencing reads extracted from a dataset created for nuclear genome (re)sequencing can be used to obtain a high quality de novo assembly of the chloroplast of the sequenced organism. Even with a relatively small overall coverage for the nuclear genome it is possible to collect more than enough reads to generate a high quality assembly that outperforms short read based assemblies. However, even with long reads it is not always possible to clarify the order of elements of a chloroplast genome sequence reliantly which we could demonstrate with Fosmid End Sequences (FES) generated with Sanger technology. Nevertheless, this limitation also applies to short read sequencing data but is reached in this case at a much earlier stage during finishing.

Dataset Information

Evolutionary conservation of the FLOWERING LOCUS C-mediated vernalization response: evidence from the sugar beet (Beta vulgaris).

Publications

Evolutionary conservation of the FLOWERING LOCUS C-mediated vernalization response: evidence from the sugar beet (Beta vulgaris).

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