April 30, 2013
Rising From The Ashes: How Plants Benefit From Forest Fires
Brett Smith for redOrbit.com - Your Universe Online
Forest fires are a major cause of plant death and destruction, but they can also be a source of life as some dormant seeds begin to germinate in the aftermath of a raging inferno.
Previous research has shown chemicals in the smoke of burning trees called karrikins“¯are responsible for this phoenix-like rebirth. Now, a new study in the Proceedings of the National Academy of Sciences has described new details on the mechanism behind karrakin-mediated seed activation.
"This is a very important and fundamental process of ecosystem renewal around the planet that we really didn't understand," said co-author Joseph P. Noel, professor and director of biology at the Salk Institute in San Diego. "Now we know the molecular triggers for how it occurs."
In the study, scientists first investigated the structure of a plant protein called KAI2 present in dormant seeds that binds to karrikins. By comparing the protein in both its bound and unbound forms, the team was able to determine how KAI2 enables a seed to recognize the presence of karrikin in its environment. According to the report, “crystallographic analyses and ligand-binding experiments” allowed the team to identify the molecular bonds between karrikins and KAI2.
“But, more than that, we also now know that when karrikin binds to the KAI2 protein it causes a change in its shape,” said co-author Yongxia Guo, a structural enzymologist and researcher at the Salk Institute.
Salk research associate and plant geneticist Zuyu Zheng, added that KAI2 shape change may cause a chain reaction of signals to other proteins in the seeds.
"These other protein players, together with karrikin and KAI2, generate the signal causing seed germination at the right place and time after a wildfire,” Zheng said.
The researchers conducted their experiments on Arabidopsis, a popular laboratory plant among researchers. However, the same karrikin-KAI2 chemical signaling is most likely found in many plant species, the scientists said.
"In plants, one member of this family of enzymes has been recruited somehow through natural selection to bind to this molecule in smoke and ash and generate this signal," Noel explained. "KAI2 likely evolved when plant ecosystems started to flourish on the terrestrial earth and fire became a very important part of ecosystems to free up nutrients locked up in dying and dead plants."
The researchers concluded their report by saying more work needs to be done in order to understand the complete mechanism from start to finish, but the existing results could still be taken into consideration by other scientists and policy makers.
Forest conservation strategies have changed considerably over the past 50 years. The US park service used to actively suppress forest fires until they realized mature forests are somewhat dependent on periodic fires that release important minerals and chemicals.
"When Yellowstone National Park was allowed to burn in 1988, many people felt that it would never be restored to its former beauty," said co-author James J. La Clair, a researcher the University of California. "But by the following spring, when the rains arrived, there was a burst of flowering plants amid the nutrient-rich ash and charred ground."