Arabidopsis thaliana
We use the model species Arabidopsis thaliana, a member of the Brassica family. Research is facilitated by:
The complete genome sequence (120 Mb DNA or 30,000 genes)
Powerful genetic resources
Functional genomics tools
Rapid life cycle and ease of culture

Discoveries are made possible with Arabidopsis that are either not possible with other plant species, or would take too long, or cost too much. Discoveries made in Arabidopsis can be transferred readily to other species such as crops.

Research Programs

We are trying to understand:

• The pathways of carbon and energy metabolism during plant growth and development.
• How the plant deploys its chemical energy for growth, storage, nutrient acquisition or defense.
• How metabolic signals are generated, perceived and interpreted by the plant, providing the means to coordinate energy metabolism, growth and defense.

Research programs include:

Oil and fatty acid metabolism, and signaling The breakdown of oil (triglyceride) and beta-oxidation of fatty acids trigger seed germination and fuel seedling growth.  Fatty acid metabolism also plays a role in plant development. Thus, we have discovered that a block in fatty acid beta-oxidation can cause dormancy in seeds, and that 3-ketoacyl CoA thiolase activity plays an important part in the control of plant growth and reproduction. We aim to understand the pathways of such metabolism, and how the signals that control plant growth are generated and perceived.

Photorespiration and tolerance of abiotic stress Photorespiration is the process of CO2 release that occurs during photosynthesis, particularly in conditions of high temperature and drought stress. We aim to understand the pathway of photorespiration in the cell, and whether the process is energetically wasteful to the plant, or if it facilitates photosynthetic metabolism under extreme conditions. We have discovered that it is possible to by-pass enzymes previously assumed to be essential, and in so doing we are learning more about the plasticity of these pathways of energy metabolism. We are also exploring the possible significance of non-enzymic CO2 release, and whether photorespiratory carbon metabolism can be modified.

Energy handling in the plant cell The three ‘energy organelles’ (chloroplasts, mitochondria and peroxisomes) function in cooperative and coordinated ways to provide the cell and hence the plant with its energy. This involves transfer of chemical energy between organelles and the cytosol, to meet the changing demands of the cell and ultimately the whole plant. We are investigating the way in which reducing power is managed in the cell, and made available for growth, storage or defense. The prime target at present is the malate dehydrogenase family, since this enzyme can provide energy in the form of malate or NADH to all compartments of the cell, and it participates in most major metabolic processes of the plant. However, many other enzymes contribute to such metabolism, and the long term goal is to understand how the system as a whole functions.

Organic acid metabolism While we traditionally think of the main energy reserves of the plant as comprising oil, starch, proteins, cellulose and sugars, another major energy supply is represented by organic acids. Like sugars, organic acids can be transported between cells and throughout the plant, and can be deployed in a range of different functions by the plant. Carboxylates accumulate in large amounts in vacuoles where they may chelate calcium, contribute to pH regulation, or provide a carbon store (such as the malate or citrate in fruits).  They can be exuded in large amounts from roots either to help solubilise soil phosphate or to chelate heavy metals such as aluminium. We are studying accumulation in leaves, transport through the plant and exudation from roots. Arabidopsis leaves accumulate large amounts of fumarate in the light and we are investigating how this is achieved and what role it plays in the energy economy of the plant.

The functions of Peroxisomes Peroxisomes are simple sub-cellular organelles that participate with chloroplasts and mitochondria in many aspects of energy metabolism and responses to abiotic stress. The functions of peroxisomes are poorly defined. Together with Harvey Millar (ARC CoE Plant Energy Biology) we are aiming to discover new peroxisome functions. We are using existing knowledge of peroxisome functions together with studies of protein targeting to peroxisomes and proteomic analysis of isolated peroxisomes, to identify as many new proteins as possible. Their functions are being investigated using molecular genetic and biochemical approaches.

Starch metabolism Starch accumulates in leaves during photosynthesis and is used up at night to fuel metabolism. New enzymes and new pathways of starch breakdown have been discovered. A potential energy ‘rationing’ system has also been uncovered. In yet another development, it has been found that starch is used as a form of energy to help cope with oxidative stresses. The goal of our research is to understand how the plant cell controls the timing and rate of starch breakdown, and thus how it achieves controlled release of energy for metabolism or defense.

Mechanism by which karrikins promote seed germination Smoke has long been known to break seed dormancy. Recently a germination-stimulating butenolide compound was isolated from smoke and several active analogues have since been discovered. We refer to this family of compounds as karrikins (from ‘karrik’, Nyungar Aboriginal for smoke), and the parent molecule is known as karrikinolide. The goal of our research is to discover the molecular mode of action of karrikins in promoting seed germination and seedling vigor. Such compounds are expected to have major applications in weed management, land reclamation and plant conservation. We collaborate closely with researchers at King’s Park and Botanic Garden, together with chemists at UWA, who jointly discovered karrikinolide.