Page 63 - PC2019 Program & Proceedings

PLANT CANADA 2019

PS10. Wednesday, July 10, afternoon session at 1:30 pm

Dr. Liam Dolan

University of Oxford, UK

Evolution and development of the earliest land plant rooting
systems

Abstract: The evolution of the first rooting systems some time before 400 million years was a key innovation
that occurred when the first complex multicellular eukaryotic photosynthetic organisms – plants – colonized
the land. The rooting systems of the earliest diverging group of extant land plants comprised unicellular tip-
growing filaments called rhizoids and are morphologically similar to cells that develop at the interface between
the plant and the soil in vascular plants – root hairs. Subsequently specialized axes – multicellular structures
that develop from self-renewing populations of cells called meristems – with evolved that carry out rooting
function. A major aim of our research is to use fossils and genes to understand key events in the evolution of
land plant rooting systems. Fossils demonstrate the variety of forms that existed and how these forms
developed. We have identified the oldest rooting structures with meristems. Genetics has allowed us to define
the regulatory mechanisms that controlled the development of the first land plant root system and
demonstrate how these mechanisms changed during the course of evolution. This positive regulatory
mechanism is preserved in most land extant plant lineages. By contrast, negative regulatory components of
the mechanism evolved independently in different lineages and some are more than 300 million years old. By
combining evidence from paleontology, genetics and development we can construct a picture for the evolution
of rooting systems in the 100 million years after plants colonized the land and radiated across the continental
surfaces.

Bio:

Liam Dolan graduated with a degree in Botany at University College, Dublin. He carried out PhD research on
plant developmental genetics in cotton and Arabidopsis at the University of Pennsylvania with Scott Poethig
and a post doc with Keith Roberts at the John Innes Centre in Norwich. After 13 years running his own research
group at the John Innes Centre, he moved to the University of Oxford as the Sherardian Professor of Botany in
2009. He was Head of the Department of Plant Sciences between 2012 and 2017.

His research uses fossils and genes to understand how roots develop and evolved in the 470-500 million years
since plants colonized the land. Fossils reveal the structure of ancient rooting systems. Genetics identifies
developmental mechanisms controlling cellular development of rooting structures. Comparative developmental
genetics illustrates how these mechanisms evolved in the course of plant evolution. A major discovery was the
demonstration that the same genetic mechanism controlled the development of the simple rooting structures
on the first land plants and the development of root hairs on the surface of extant vascular plant roots.
https://www.plants.ox.ac.uk/people/liam-dolan

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