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The evolution of nuclear auxin signalling
Ivan A Paponov1, William Teale, Daniel Lang
1Botany, Faculty of Biology, University of Freiburg, Schänzlestrasse 1, 79104 Freiburg, Germany. ivan.paponov@biologie.uni-freiburg.de
BMC Evolutionary Biology
|June 5, 2009
Summary
The evolution of auxin signaling in plants reveals that flowering plants developed rapid responses after diverging from mosses. Non-seed plants like Physcomitrella patens and Selaginella moellendorffii possess unique auxin response mechanisms.
Area of Science:
- Plant Biology
- Evolutionary Biology
- Molecular Genetics
Background:
- The plant hormone auxin is critical for plant growth and development.
- Understanding auxin signaling evolution requires comparing key regulators like AUXIN RESPONSE FACTOR (ARF) and AUXIN/INDOLE-3-ACETIC ACID (Aux/IAA) genes across diverse plant lineages.
- This study investigates these gene families in flowering plants, the moss Physcomitrella patens, and the lyophyte Selaginella moellendorffii.
Purpose of the Study:
- To elucidate the evolutionary history of auxin signaling pathways.
- To compare the genetic components of auxin response in seed plants versus non-seed plants.
- To identify novel mechanisms of auxin action in early land plants.
Main Methods:
- Comparative genomics of ARF and Aux/IAA gene families.
- Phylogenetic analysis across Physcomitrella patens, Selaginella moellendorffii, and flowering plants (Arabidopsis thaliana, poplar).
- Analysis of positive Darwinian selection on ARF genes.
Main Results:
- The rapid auxin transcriptional response characteristic of flowering plants evolved in vascular plants post-divergence from mosses.
- Physcomitrella patens and Selaginella moellendorffii possess N-terminally truncated ARF activators, indicating a distinct nuclear auxin signaling mechanism.
- Positive selection identified in specific ARF clades (IIa, Ib) of Arabidopsis thaliana and poplar suggests neofunctionalization drove auxin signaling evolution in flowering plants.
- Phylogenetic profiles of primary auxin-responsive genes (GH3, SAUR, LBD) differ across the studied plant groups.
Conclusions:
- Physcomitrella patens possesses the core components for rapid auxin response, but with a distinct transcriptional control mechanism due to spatially separated functional domains.
- Selaginella moellendorffii appears to encode proteins compatible with both moss-like and flowering plant-like auxin regulation methods.
- These findings highlight the evolutionary plasticity of auxin signaling and suggest potential alternative regulatory strategies in early land plants.
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