Symposium III: Hormone Crosstalk

Abs # 30003: Crosstalk between development and hormones: Is it meaningful or just gossip?"

Presenter:	McCourt, Peter , mccourt@botany.utoronto.ca
Authors	McCourt, Peter  (A)
Affiliations:	(A): Department of Botany, University of Toronto

Signal transduction pathways have been described quite simply to consist of three phases: perception of the input signal at a receptor, propagation of the signal through molecular commands, and change in a specific output response often through the control of a transcription factor. Using this framework in combination with information derived from mutant analysis, pathways for the transduction of hormone signaling in plants have been created. Although this approach has also provided a good framework for some pathways, such as ethylene signaling, this approach has not yielded a clear idea of how other hormone pathways are put together. For example to date, fifty genes have been identified that are thought to influence ABA sensitivity in Arabidopsis. Does this mean there are fifty genes required to transduce the ABA signal into a cellular response? One possible reason for the high number of mutants with altered ABA sensitivity is that many of these genes are not directly involved in ABA signaling but impinge on ABA sensitivity indirectly by influencing the development of particular cell types. For example, genes involved in establishing the developmental competence of a cell to ABA could, in principle, alter ABA responsiveness. In this talk I will cite examples where known ABA response genes have now been shown to be involved in other developmental pathways and their influence on ABA signaling is at best peripheral. For example, the ABI3 gene, which was originally identified as an ABA related transcription factor involved in establishing ABA responsiveness in the seed is also expressed outside of the seed development and plays roles in auxin regulated events such as lateral root development. I will show data on how genes involved in leaf development can affect ABA synthesis and how in turn other hormones can influence expression of these genes. These results blur the line between development and hormone signaling and suggest it is the interaction of hormones with developmental regulators that control the overall growth and development of the plant.