Researchers at The University of Western Australia in collaboration with scientists at CSIRO Plant Industry have made a discovery that will change the way scientists look at the role of respiration in regulating plant responses to disease.
Every minute as we breathe our bodies make “reactive oxygen species”, which are toxic oxygen-based chemicals. Our bodies have inbuilt defence systems which rapidly degrade these chemicals using antioxidant vitamins, therefore preventing cell damage which can lead to cancer and aging.
But the latest research has found that in plants, while reactive oxygen species are also produced during respiration, they play a positive role in plant defence if properly controlled.
The research, which was co-funded by CSIRO, the Australian Research Council and the Grains Research and Development Corporation, was published this week in the prestigious international journal Proceedings of the National Academy of Sciences USA (Gleason et al 2011, June 13).
The research, led by Winthrop Professor Karam Singh (CSIRO and UWA) and Winthrop Professor Harvey Millar (UWA), focused on a respiration gene in the mitochondria, which is essential for energy production in plants, yeast and animals. In humans, a mutation in this gene leads to a range of neurological disorders.
Remarkably, the researchers found that plants with a mutation in this gene grew normally in good conditions, but under pathogen attack, could not form the reactive oxygen chemicals required to properly activate plant defence against fungal and bacterial pathogens.
“Our research demonstrates a key role for plant mitochondria for responding to diverse types of chemical and disease stresses through the production of reactive oxygen chemicals,” said co-first author Dr Cynthia Gleason from CSIRO.
“We show that chemicals commonly considered to be ‘bad' can sometimes be ‘very good',” said co-first author Dr Shaobai Huang from UWA. “Despite their potential for damage, without the ability to generate these toxic chemicals from the mitochondria, plants are unable to coordinate an attack response.”
“As long as antioxidant molecules are working to disarm these toxic chemicals after their job is done in cellular signalling, they can have an important and beneficial role in the cell,” UWA Winthrop Professor Harvey Millar said.
The research was undertaken at CSIRO, the ARC Centre of Excellence for Plant Energy Biology and the UWA Institute of Agriculture and provides new targets for regulating plant responses to disease. It shows that cellular “trash” can also turn out to be treasure.