Paleobotany in the Post-Genomics Era
Rothwell, Gar W. , Sanders, Heather , Wyatt, Sarah , Lev-Yadun, Simcha .
Fossil record of growth regulation and the evolution of modern plant structure.
APPRECIATION for the role of ontogeny in plant evolution recently has been heightened by advances in developmental molecular techniques, and by an increasing understanding of relationships between gene activity, tissue patterning, and mature plant form. A growing number of structural features are now understood in terms of the regulatory mechanisms by which they are produced. When such structures are identified in the fossil record, they can be regarded as "finger prints" for particular gene mediated regulatory pathways and for the specific developmental alterations that underlie the evolution of plant structure. Polar auxin regulation of cambial activity is represented by circular patterns of tracheary elements that occur in wood immediately above buds and branch junctions. This feature reflects the developmental origin of wood in seed plants and provides additional support for monophylesis of lignophytes. Likewise, the occurrence of similar circular patterns in the wood of tree sized fossil equisetophytes and arborescent lycophytes, provides direct developmental evidence that polar auxin regulated secondary vascular tissue production in all of these groups and that the mechanism predated evolution of secondary tissues in each. Finger prints of growth regulation during primary vascular development also are preserved in the fossil record. These occur as protoxylem strands within stems of the most primitive seed plants. Such protoxylem strands are evidence for auxin regulation of vascular tissue production during apical meristematic activity. Differences in the positions of protoxylem strands among fossil seed plants reflect changes in auxin regulation that are associated with the evolution of eusteles from protosteles. Studies such as these provide a vehicle for fully integrating evolutionary pattern and process, thus reaffirming the vital role of paleontology in studies of evolutionary plant biology.
Log in to add this item to your schedule
1 - Ohio University, Department of Environmental & Plant Biology, Porter Hall, Richland Avenue, Athens, Ohio, 45701-2979, USA
2 - University of Haifa-Oranim, Department of Biology, Faculty of Science and Science Education, Tivon, 36006, Isreal
Presentation Type: Symposium or Colloquium Presentation
Date: Wednesday, August 2nd, 2006
Time: 9:15 AM