Proceedings of the National Academy of Sciences of the United States of America

About the PNAS Member Editor
Name Estelle, Mark
Location University of California, San Diego
Primary Field Plant Biology
Secondary Field Plant, Soil and Microbial Sciences
 Election Citation
Estelle studies the plant hormones involved in growth and development. His research group elucidated the molecular mechanisms by which the plant hormone auxin is perceived by plant cells and is transduced into responses. They are now working to understand the systems that mediate development at the level of the organism.
 Research Interests
As in all organisms, plant development is genetically regulated. However, because plants do not move, their development is also remarkably responsive to the environment. I am interested in the role of plant hormones in both of these aspects of development. Auxin was the first plant hormone to be discovered and has been implicated in virtually every stage of plant growth and development. My laboratory has used the genetically tractable plant Arabidopsis thaliana to identify auxin response pathways. Our work demonstrated that auxin response depends on the rapid degradation of transcriptional repressors called the Aux/IAA proteins. Repressor degradation requires a ubiquitin protein ligase or E3 called SCFTIR1. The function of E3s is to bind protein substrates and promote their ubiquitination and degradation. Recent results indicate that SCFTIR1 acts as an auxin receptor. Auxin binds to the SCF and stabilizes its interaction with the Aux/IAA substrates, thus promoting their degradation. This is both a novel mechanism of hormone perception and E3 regulation. The lab is now turning its attention to the complex transcriptional networks that mediate auxin growth responses. Our ultimate goal is to understand the systems that mediate development at the level of the organism.

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