Some plants are adapted to wait through the winter before their genetic programs for flowering are initiated. But the duration of winter varies with location; thus, to avoid flowering too late into the summer or exposing blossoms to frost, the adaptation needs to hold the flowers off for just the right amount of time. Working with Arabidopsis thaliana, Coustham et al. identified a quantitative mechanism that “counts” off the duration of winter. FLC, a repressor of flowering, carries sequence polymorphisms that direct epigenetic events. Plants with fewer of these polymorphisms are adapted to short winters, and plants with all four polymorphisms are adapted to long winters.
V. Coustham, P. Li, A. Strange, C. Lister, J. Song, C. Dean, Quantitative modulation of polycomb silencing underlies natural variation in vernalization. Science 337, 584–587 (2012). [Abstract] [Full Text]