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Posted by ejchapman on 14 May 2012 at 15:55 GMT

During plant growth and development, the hormone auxin is associated with a variety of growth and developmental processes including cell identity determination, organ initiation, and tropism. In recent years, we have made significant progress in our understanding of the molecular mechanism of auxin action. We now know that hormone-receptor interactions directly regulate the turnover of a family of transcriptional repressors and thereby control expression of auxin-responsive genes. We are using Arabidopsis hypocotyls to explore the function of the auxin-regulated transcriptome in cell expansion and plant growth. Here, we characterize the hypocotyl elongation response to auxin and identify auxin receptors and transcriptional regulators required for this growth response. We profile the transcriptome in elongating hypocotyls and present evidence that auxin promotes cell expansion by regulating expression of genes associated with growth. We further show that this regulatory effect occurs through both gibberellin-dependent and -independent pathways. With these results we identify factors required for auxin perception, signal transduction, and transcriptional output in a specific auxin-mediated growth response. We also establish the hypocotyl as a model system for further studies of hormone signaling during cell expansion, and elucidate striking parallels between the auxin-regulated and the growth-associated transcriptome.

Competing interests declared: I am an author on this paper.
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