Hormones influence virtually every aspect of plant growth and development. The elucidation of the molecular mechanisms controlling the biosynthesis and perception of these hormonal signals, and how these signals are integrated with each other and with other developmental and environmental signals remain fundamental questions in plant biology. There are three main areas of focus to the research in my laboratory: the regulation of ethylene biosynthesis, the analysis of two-component elements in Arabidopsis and the analysis of the signaling mechanisms underlying the phytohormone cytokinin. Using a combination of genetic, molecular, genomic, and biochemical approaches we are attempting to elucidate elements involved in these processes and ultimately to understand how these elements contribute to control plant growth and development.

Cytokinins, N6-substituted adenine derivatives, have been implicated to play a role in almost all aspects of plant growth and development. We are characterizing the cytokinin response pathway. A signaling pathway from the cell surface to the nucleus has been defined, and surprisingly it has been found to be similar to bacterial two-component signaling systems. We are determining how this signaling system and cytokinin itself works to regulate plant growth and development, and are elucidating the interactions among the signaling components and the targets of this signaling pathway. We are also examining the role of the other two-component homologs in the growth and development of Arabidopsis using an integrated approach.

The simple gas ethylene has been recognized as a plant hormone since the turn of the century. It has been shown to influence a diverse array of plant processes, such as leaf and flow senescence and abscission, fruit ripening and the response to a wide variety of stresses. Almost all plant tissues have the capacity to make ethylene, although in most cases the amount of ethylene produced is very low. There is a diverse group of factors that increase the level of ethylene biosynthesis, including other hormones (auxin, cytokinin, ethylene), numerous stresses, as well as various developmental events. We have identified a number of genes that are important in the post-translational control of the ethylene biosynthetic pathway and are studying how these genes modulate ethylene production.