The Footprints of Winter
Epigenetic marks laid down during the cold months of the year allow flowering in spring and summer.
Many plants that grow in climates with a cold winter require growth for several months at low temperatures—a process called vernalization—to promote flowering in spring, when days lengthen and temperatures increase. Without this period of cold, plants would grow leaves in the spring, but would fail to flower. This phenomenon, familiar to every horticulturist, was difficult to explain with genetics alone; something occurred during those cold months that left a mark, which, in effect, released a switch that permitted flowering in spring. In recent years, the field has looked beyond the genome and found that vernalization is controlled by a wide range of epigenetic mechanisms.
Researchers studying the genetics of flowering found that the flowering switch was controlled by two central players—the genes FLOWERING LOCUS T (FT) and SUPPRESSOR OF CONSTANS1 (SOC1), which were held in the “off” position by the product of the gene called FLOWERING LOCUS C (FLC).1 Through a process that is initiated in the winter, and is complete by spring, FLC expression is reduced to levels that release the switch, allowing expression of FT and SOC1 to drive flowering. Whatever molecular mechanism reduces FLC expression, it is clearly sensitive to environmental input: cold temperature.
|This article is adapted from an upcoming review in F1000 Medicine Reports. It will be available for citation at f1000.com/reports