PSL Research Interests

We use molecular, biochemical, and genetic strategies to study how plants grow and respond to changes in their environment, focusing on the roles played by the plant hormones cytokinin and ethylene. I find several aspects of plant hormone research particularly rewarding. First, we are currently in a golden age for plant hormone research because, although some of these hormones were identified a century ago, only recently has significant progress been made in identifying the proteins involved in sensing and transducing the signals. Second, our research is relevant to solving real-world agricultural problems, such as the control of ripening and senescence. Finally, I enjoy the science-fictional aspect of our research: each cell is like its own alien world and it is our job to decipher the rules that govern communication within this world.  

Research Projects:

1. Mechanism of cytokinin signal transduction.
Cytokinins regulate cell division and metabolism, stimulate chloroplast development, modulate shoot and root development, and delay senescence. The cytokinin signal is relayed from membrane to nucleus via a phosphorelay making use of receptors, phospho-transfer proteins, and type-B response regulators. Our research is focused on the type-B response regulators (ARRs), which act as transcription factors. We are employing genetic and genomic approaches in the dicot Arabidopsis and the monocot rice to assess how these genes function in plant growth and development, and how cytokinin signaling can be modulated to control such agronomically important characteristics as grain yield. We are also determining the roles of other transcription factors that act in the transcriptional cascade initiated by the type-B response regulators. Some of these transcription factors regulate division at the stem cell niche; others regulate chloroplast development..

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2. Mechanism of ethylene signal transduction.
Ethylene serves as a gaseous hormone in plants, and is perhaps most widely known for its role in the ripening of such fruit as tomatoes, bananas, and apples. Ethylene receptors have been identified, and my laboratory is determining how these transduce the ethylene signal. For this purpose we are characterizing the receptors in terms of structure, regulation, interactions, and the effects of mutations upon downstream signaling. These studies will help build a mechanistic model for how ethylene is perceived and the signal transduced in the plant.

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