In higher plants, growth is coordinated both by developmental cues and by environment. The focus of our research is to understand signalling mechanisms regulating plant cell division and growth. We are analysing two such signalling pathways in Arabidopsis, the mitogen-activated protein kinase (MAPK) cascade and recently we started working on the phospholipid-activated protein kinase signalling pathway, involving PDK1. These two branches of signalling are the major controller of cell growth and cell division in yeast and in animal cells, but their function in plants is still elusive. We use reverse-genetic approaches to up and down-regulate the activity of selected components of these signalling pathways and thus to study their function. We are also looking for new and possibly plant-specific components and targets of the MAPK and PDK1 signalling pathways, using protein interaction screens and proteomics. We have developed novel methods to monitor cell divisions and cell growth in plants, using the growth- or cell cycle-dependent expression of the green fluorescent protein as a marker, which greatly aid the analysis of the function of growth-signalling pathways.

Signalling pathways influence cell divisions through conserved cell cycle regulators. We found, that one of the cyclins is rate limiting for entry into mitosis, and thus potentially could be targeted by signalling pathways to influence cell division and we are interested to find this out using Arabidopsis as a model system.

Understanding the mechanisms that control the size difference in plants will be challenging but potentially very useful. It might permit the development of crop species with a better stress tolerance and growth to achieve much larger stature. It may also allow the modification of the growth habit of small or slow-growing species that has useful properties but have not been domesticated because of low yield.

L. Bogre is a co-ordinator on a European Framework V project (Growth vigour environment) and this consortium made further initiatives to develop plant signalling networks in Europe.