

About the PNAS Member Editor
Name Amasino, Richard M.
Location University of Wisconsin-Madison
Primary Field Plant, Soil and Microbial Sciences
Secondary Field Plant Biology
 Election Citation
Amasino has pioneered exploration of the genetic mechanisms that control flowering and impart a molecular "memory of winter." His work has advanced our understanding of flowering and plant aging, and has significant potential applications in agriculture.
 Research Interests
My research focus has been the regulation of plant development, particularly the transition to flowering. Many plant species have evolved the ability to regulate flowering in response to environmental cues such as changes in day-length or temperature. For example, certain plant species do not initiate flowering unless they have experienced the prolonged cold of winter. This promotion of flowering by prolonged exposure to cold is known as vernalization. A vernalization requirement ensures that in temperate regions flowering does not occur in the fall season. Our studies of floral induction in Arabidopsis thaliana revealed a gene, FLOWERING LOCUS C (FLC) that plays a key role in establishing a vernalization requirement. FLC encodes a potent repressor of flowering that is active in autumn. During winter, vernalization causes FLC repression which, in turn, results in the acquisition of competence to flower in the spring. The repression of FLC by vernalization is epigenetic in the sense that it is mitotically stable in the absence of the inducing signal, cold exposure. In the next generation, FLC is reset to the expressed state. We have shown that the different epigenetic states of FLC expression in fall, winter and spring are associated with a series of modifications to FLC chromatin, and we have characterized many of the components that are required to establish these distinct states of FLC expression. For example, the cold-mediated repression is initiated by a gene, VERNALIZATION INSENSITIVE 3 (VIN3) that has the unique property of being expressed only after prolonged exposure to cold. Most organisms can sense cold, but plants have evolved the additional ability to "count", at a cellular level, the number of days they have exposed to cold, and VIN3 induction during winter is an output of this cold measurement system.

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