AUSTRALIA: `Smoke detector' gene in plants

Researchers at the University of Western Australia have discovered a gene that allows dormant seeds buried in the soil to detect germination stimulants called karrikins in bushfire smoke. The same gene has also been found to provide the means for plants to respond to a growth hormone called strigolactone which controls shoot branching, the formation of beneficial fungal associations and germination of parasitic weeds.

The findings reinforce the view that smoke from bushfires not only signals destruction but also provides the stimulus for new vigorous plant growth with the following rains. UWA plant biologist Dr David Nelson, who led the research, selected plants that had lost the ability to respond to karrikins and then searched for the defective gene in those plants.

"It was a 'eureka moment' when I looked at the DNA sequence of the defective gene and realised what we had discovered," Nelson said. "That one gene has two very different functions, one in fire ecology and the other in plant development."

The findings reflect the fact that the karrikins and the strigolactone hormone have similar chemical structures. Their slight differences allow them to perform different roles but their similarities mean they are detected by one plant chemical detection system. Ultimately the detector system allows the plant to distinguish between these signals and respond appropriately.

Professor Steven Smith said the findings gave biologists a new perspective on how to adapt plant and fire management and responses: "It will help us to understand how plant communities will respond in future to the increasing incidents of fire, how we should use fire to manage plants, and to investigate new methods for controlling weeds," Smith said.

The discovery was published in Proceedings of the National Academy of Sciences.