RESUMO
Life cycle adaptation to latitudinal and seasonal variation in photoperiod and temperature is a major determinant of evolutionary success in flowering plants. Whereas the life cycle of the dicotyledonous model species Arabidopsis thaliana is controlled by two epistatic genes, FLOWERING LOCUS C and FRIGIDA, three unrelated loci (VERNALIZATION) determine the spring and winter habits of monocotyledonous plants such as temperate cereals. In the core eudicot species Beta vulgaris, whose lineage diverged from that leading to Arabidopsis shortly after the monocot-dicot split 140 million years ago, the bolting locus B is a master switch distinguishing annuals from biennials. Here, we isolated B and show that the pseudo-response regulator gene BOLTING TIME CONTROL 1 (BvBTC1), through regulation of the FLOWERING LOCUS T genes, is absolutely necessary for flowering and mediates the response to both long days and vernalization. Our results suggest that domestication of beets involved the selection of a rare partial loss-of-function BvBTC1 allele that imparts reduced sensitivity to photoperiod that is restored by vernalization, thus conferring bienniality, and illustrate how evolutionary plasticity at a key regulatory point can enable new life cycle strategies.
Assuntos
Adaptação Biológica/fisiologia , Agricultura/métodos , Beta vulgaris/fisiologia , Evolução Biológica , Flores/fisiologia , Genes Reguladores/genética , Proteínas de Plantas/genética , Adaptação Biológica/genética , Sequência de Aminoácidos , Análise do Polimorfismo de Comprimento de Fragmentos Amplificados , Sequência de Bases , Beta vulgaris/genética , Mapeamento Cromossômico , Cromossomos Artificiais Bacterianos/genética , Clonagem Molecular , Primers do DNA/genética , Flores/genética , Marcadores Genéticos/genética , Haplótipos/genética , Immunoblotting , Modelos Biológicos , Dados de Sequência Molecular , Fenótipo , Fotoperíodo , Filogenia , Estações do Ano , Seleção Genética , Alinhamento de Sequência , Análise de Sequência de DNARESUMO
Cultivated beets (Beta vulgaris ssp. vulgaris) are unable to form reproductive shoots during the first year of their life cycle. Flowering only occurs if plants get vernalized, that is, pass through the winter, and are subsequently exposed to an increasing day length (photoperiod) in spring. Here, we show that the regulation of flowering time in beets is controlled by the interplay of two paralogs of the FLOWERING LOCUS T (FT) gene in Arabidopsis that have evolved antagonistic functions. BvFT2 is functionally conserved with FT and essential for flowering. In contrast, BvFT1 represses flowering and its down-regulation is crucial for the vernalization response in beets. These data suggest that the beet has evolved a different strategy relative to Arabidopsis and cereals to regulate vernalization.
