Plant hormones: Dissecting the gibberellin response pathway

Plant development is amazingly plastic — for example, identical pine seeds can give rise to a majestic tree in a forest or a scraggly bush on a rocky cliff. How is plant growth and development regulated so as to be capable of achieving such dramatically different endpoints? One factor that has emerged as a key regulator of plant form is gibberellin (GA; see Figure 1 inset for the chemical structure). GA acts in both a continuous and a discrete manner during the life cycle of a plant. During the entire life cycle, GA promotes cell elongation; this role is particularly important given that plant form is entirely dictated by cell elongation and cell division in the absence of cell mobility. GA also acts as a regulator of key transition points in the plant life cycle by its ability to promote the germination of seeds and induction of flowering. The characterization of GA signaling pathways would greatly facilitate an understanding of how GA regulates these diverse processes.