Establish the link between jasmonate signalling and the cell cycle

Plant growth and therefore yield, is strongly dependent on both genetic and environmental conditions. It is frequently observed that stresses not only induce plant resistance but also affect growth rate and cell division. The external signals that predicate stress act not only on proteins that are involved in cell division, but also trigger response in differentiated tissue, and in some way this response is then coupled to the regulation of the cell cycle. Jasmonate (JA) production can be considered as a 'switch' that when triggered acts to reprogramme plant metabolism, growth and development. Generally, stress tends to stop cells from getting bigger, and stressed plants can be severely dwarfed. Mutants in JA signalling are severely compromised in responding to stress and several of them are stunted. A role for JAs in cell cycle progression is just emerging. JA blocks cell cycle progression by inhibiting G1/S and G2/M transitions in tobacco cells (Swiatek A et al (2002) Plant Physiol. 128: 201-211, see Figure). While the molecular mechanisms and downstream responses have not been clarified yet, we are excited by the likelihood that JA is a distress signal, a physiological role of which is to block cell cycle, slowing vegetative growth during defense responses. JA also suppresses cell proliferation in human cancer cell lines, opening a door for the potential use of JAs as therapeutics.

Role of Jasmonate in the cell cycle.

In this project, in a targeted approach, a combination of molecular biology with physiological, biochemical and cell biology approaches is used to establish the role of JA signalling components in cell cycle in Arabidopsis. In a functional genomics approach we are also investigating the role of cell cycle regulators in JA-mediated stress and development.

Engineering jasmonate-mediated production of secondary products in plants

Plants produce many small molecules useful as pharmaceuticals, insecticides, dyes, flavours, and fragrances. JAs are the fragrance from scented jasmine flowers long used in the perfume industry. In recent years, the action of JAs as inducers of plant secondary (2°) metabolism has started receiving attention (Devoto and Turner 2004, Physiol Plant, 123: 161-172). Expression profile analysis of Arabidopsis genes that are strongly induced by wounding and methyl JA revealed that approximately 25% encode enzymes of, or regulating, 2° metabolism. These include genes for the production of 2° products such as alkaloids, phenolics, and terpenoids (Devoto et al. 2005, Plant Mol Biol, 58:497-513).

From Vainstein et al. 2001, Plant Phys, 127: 1383-1389

In this project, genomics, chemical analysis, and bioinformatics are used to manipulate the pathways for the production of several classes of natural compounds of importance to obtain therapeutic drugs as well as fragrances. A corollary of this research is the likely identification of genes and 2° metabolites active in plant defence. The model plant Arabidopsis is used in this approach that has the potential to be extended to other plant species. In this approach, plant material substitutes for chemically synthesized compounds.

Construction of high-order gene regulatory networks related to plant responses to biotic, abiotic stresses and hormones

Large-scale genomic analyses have identified hundreds of genes that are differentially regulated by environmental stresses. Their complex expression patterns suggest that stress tolerance and resistance are controlled at the transcriptional level by a complicated gene regulatory network.

The next steps towards understanding stress biology at the systems level are reconstructing the network and then verifying the roles the various genes play in the network. In this project we focus on stress signalling networks regulated by plant distress signals such as JAs mediating responses to biotic or abiotic stimuli, in the model plant Arabidopsis thaliana.

We use transcriptomics and proteomics experimental data for Arabidopsis to identify novel genes involved in stress signalling. Gathered results are integrated with computational biology to construct a signalling network from receptor activation to the ultimate gene expression. This project is in collaboration with Drs Alberto Paccanaro and Hugh Shanahan at the Computer Science group at Royal Holloway.