Biological Sciences

Detlef Weigel Assistant Professor, The Salk Institute e-mail: weigel@salk.edu

     Flowers are not only the organs of plant reproduction, but since they give rise to fruits and seeds, they also provide the majority of calories that humans consume. The first step in flower development is the switch from the vegetative phase of the plant life cycle to the reproductive phase. This switch is caused by a still poorly understood process termed floral induction, which results from the plastic interaction of environmental signals with an endogenous clock. Once this switch has taken place, individual flowers are initiated at selected sites within the growing plant, followed by the elaboration of flower-specific organ patterns. 

     A breakthrough in understanding floral induction was our finding in 1995 that the activity of the flower-identity gene LEAFY is sufficient to initiate flower development in a variety of different species, which indicated that many of the basic mechanisms controlling floral induction are conserved despite substantial differences in the phenomenology of flowering among different species. LEAFY induces flowers not only in Arabidopsis, which normally flowers within a few weeks after germination, but
also in aspen trees, which normally flower only after eight to twenty years of vegetative growth. 

     My laboratory continues to work in the areas of floral induction, flower initiation and floral patterning. Our primary model system is Arabidopsis, whose complete genome sequence will be soon available, and for which mutants are rapidly generated by both forward and reverse genetics. In the area of floral induction, we are using new types of mutant screens such as activation tagging to identify components of the floral induction machinery, with the goal of understanding how floral induction regulates the activity of flower-identity genes. In the area of floral patterning, we are dissecting the molecular mechanisms by which early-acting genes such as LEAFY and UFO control the expression of later-acting homeotic genes. 

     A substantial part of our work is carried out in collaboration with the laboratories of Marty Yanofsky and Joanne Chory. The ultimate goal of these studies is to achieve a complete description, at the genetic and molecular level, of the mechanisms that underlie the formation of flowers in all higher plants. 

     Lee, I., Wolfe, D. S., Nilsson, O. and Weigel, D. (1997). A LEAFY co-regulator encoded by UNUSUAL FLORAL ORGANS. Current Biology 7: 95-104. 

     Weigel, D. and Nilsson, O. (1995). A developmental switch sufficient for flower initiation in diverse plants. Nature 377: 495-500.