How Cool Is That: An Interview with Caroline Dean

Having grown up in Pennsylvania, I recall that late winter’s delight in spotting a purple crocus piercing through desiccated gray snow, a harbinger for warmer days ahead. The eruption of the crocus, the bloom of the magnolia, and the flowering of winter wheat are all examples of plant processes that are not simply delayed by winter, but indeed require a sustained period of cold to proceed. Today’s interview journeys into the molecular underpinnings of one such cold-dependent process: ‘‘vernalization.’’ Our guide is Caroline Dean from the John Innes Centre in Norwich in the United Kingdom, and our destination is an ,10-kb genomic stretch of the humble Arabidopsis thaliana, a small white-flowering bit of greenery also known variously as thale or mouse-ear cress. A little background is in order here, as perhaps you, like me, had never heard the term vernalization. During the development of flowering plants, shoot growth occurs at the apical meristem, an undifferentiated mass of cells that can divide to make more stems, leaves, or flowers. While some plants are ‘‘rapid cyclers’’—i.e., they flower quickly after a short growth period—others require a duration of cold before they can flower, an evolutionary adaptation that allows them to resist flowering until the winter has ended. Often, varieties within a single species can exhibit one behavior or the other, such as spring and winter wheat, only the latter of which requires vernalization. Accessions of Arabidopsis vary in their vernalization requirement too, depending upon whether they grow along the Mediterranean coast or above the Arctic Circle, for example. A few decades ago, when Arabidopsis emerged as the plant of choice for molecular geneticists, Dean (Image 1) began to question how vernalization works at the mechanistic level: what genes are required for vernalization and how do vernalizing plants sense and remember the cold? She and her colleagues attacked the problem via three genetic routes, all of which ultimately converged on the regulation of a single gene, FLC (FLOWERING LOCUS C), whose gene product is a repressor of downstream flowering genes. The ‘‘overwintering’’ accessions respond Citation: Gitschier J (2013) How Cool Is That: An Interview with Caroline Dean. PLoS Genet 9(6): e1003593. doi:10.1371/journal.pgen.1003593