Dr. Stefan Kepinski
Auxin and plant development
The plant hormone auxin is central to the control of plant growth and development. At the cellular level, auxin can regulate cell division, cell expansion and can trigger specific differentiation events. In addition, auxin is unique among plant hormones in that its transport is both tightly regulated and polar, allowing auxin to carry directional intercellular and longer distance signals, and thus to act as a regulator of pattern formation. The largest component of this influence over diverse developmental events stems from auxin’s ability to regulate differentially the expression of hundreds of genes. We have previously shown that auxin prompts the expression of auxin-regulated genes by causing the ubiquitin-dependent proteolysis of Aux/IAA transcriptional repressor proteins and that this is catalysed by the SCF-type ubiquitin-ligase complex SCFTIR1. More recently we have also shown that the regulation of the interaction between SCFTIR1 and Aux/IAAs depends of the direct binding of auxin to the F-box protein TIR1, and hence that TIR1 is the auxin receptor for this response.
A key question in plant biology is how the hormone auxin controls such a diversity of developmental events. Research in the Kepinski lab is focused on understanding how the specificity which can account for this control arises in the auxin signalling system. Although the current qualitative model of this complex system provides a conceptual framework for understanding how auxin can turn genes on and off, it is unclear how and where specific information is carried in the system and thus how auxin pulses of differing length and amplitude can be translated into quantitatively different genomic outputs both within and between various developmental contexts. To address these questions, we are obtaining quantitative and cell-type-specific genomic and biochemical data to parameterize comparative mathematical models of auxin response in juxtaposed developmental contexts to understand how auxin operates throughout development. Because of the desire to model, as far as possible, at the level of the single cell and with realistic binding preferences among protein components, the group in heavily involved in single-cell-type sampling techniques and in vitro and in vivo quantification of protein interactions and abundance. We work closely with modellers at CPIB in Nottingham and the Computational Biology Group at Leeds to integrate the experimental and theoretical aspects of the work.
Current projects include
- Quantitative and contextual modelling of transcriptional responses to auxin (BBSRC) collaborations with John King, Applied Maths/CPIB Nottingham and Karin Ljung, Umeå, Sweden
- Understanding specificity in auxin perception (BBSRC) collaboration with Richard Napier, Warwick HRI
- Auxin signalling in the shoot apical meristem (White Rose Consortium) collaborations with Andrew Fleming, Sheffield and Keith Lindsey, Durham
- Novel regulators of auxin response (BBSRC DTG) collaboration with Minami Matsui, RIKEN Plant Science Centre, Yokohama