Natural variation in autumn expression is the major adaptive determinant distinguishing Arabidopsis FLC haplotypes.

Abstract

In <i>Arabidopsis thaliana,</i> winter is registered during vernalization through the temperature-dependent repression and epigenetic silencing of floral repressor <i>FLOWERING LOCUS C (FLC)</i>. Natural Arabidopsis accessions show considerable variation in vernalization. However, which aspect of the <i>FLC</i> repression mechanism is most important for adaptation to different environments is unclear. By analysing <i>FLC</i> dynamics in natural variants and mutants throughout winter in three field sites, we find that autumnal <i>FLC</i> expression, rather than epigenetic silencing, is the major variable conferred by the distinct Arabidopsis <i>FLC</i>haplotypes. This variation influences flowering responses of Arabidopsis accessions resulting in an interplay between promotion and delay of flowering in different climates to balance survival and, through a post-vernalization effect, reproductive output. These data reveal how expression variation through non-coding cis variation at <i>FLC</i> has enabled Arabidopsis accessions to adapt to different climatic conditions and year-on-year fluctuations.