Abstract
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.
Highlights
An important debate in evolutionary biology is the influence of few major-effect versus many minor-effect changes in the adaptation of organisms to different environments [1]
QTL profile in accessions selected for their distinct vernalization response Four Arabidopsis accessions Lov-1, Ull-2-5, Var-2-6 and Edi-0 had previously been selected for QTL analysis [10]
The accessions had been selected as they showed particular features of interest in their vernalization response: Lov-1 is insensitive to 4 weeks of cold but responded strongly to five or more weeks of cold; Ull-2-5 is very late flowering even after extensive vernalization (10 weeks of cold); Var-2-6 is typical of many Scandinavian accessions showing a quantitative acceleration with increasing weeks of cold, saturating at 10 weeks; Edi-0 is very late-flowering when not exposed to low temperature but responded strongly to 4 weeks of cold
Summary
An important debate in evolutionary biology is the influence of few major-effect versus many minor-effect changes in the adaptation of organisms to different environments [1]. An important adaptive trait in plants is the timing of flowering This significantly influences their fitness and so is tightly regulated, variation in this trait is required to enable plants to adapt to different environmental conditions. The regulatory network and molecular mechanisms mediating the impact of environmental cues on the timing of the floral transition have been extensively studied in Arabidopsis [2]. Different Arabidopsis accessions show variation in the length of cold required to satisfy the vernalization requirement and this correlates with the ability to epigenetically silence FLC [6]. Initial analysis of four F2 populations mapped the QTL contributing to the variation in FLC epigenetic silencing to broad genomic regions and concluded that, unexpectedly, none of them corresponded to the trans-factors currently known to regulate vernalization [10]. Further analysis was required to identify the genes involved
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