Learning Backward: How Mold Can Teach Us About Climate Change
To the untrained ear, “reverse ecology” sounds like something out of a time-bending science fiction movie. But in John Taylor’s genomic research lab, it’s a powerful new tool in evolutionary genetics research, one that could be used to help monitor the effects of climate change and habitat destruction.
In a study published in the Proceedings of the National Academy of Sciences in January 2011, Taylor and his team used 48 different strains of wild Neurospora crassa from three far-flung regions to show that it’s possible to determine an organism’s adaptive traits by looking first at its genome and then checking for variations across a population.
They found a gene that is known to indicate cold tolerance, and then showed that members of the population that contained unique variants lived in regions with lower minimum temperatures—up to 9 degrees Celsius on average—and were able to grow better at cold temperatures than were strains found in more tropical climates.
“The normal route for adaptation studies is to first look at obvious differences—such as hair or skin color—between two closely related organisms,” said Taylor, a professor of plant and microbial biology (PMB). “Then we look at the environment in which the organism lives to see if it might explain those differences, and finally, we examine the genes to see if there is evidence of natural selection.”
For example, the researchers referred to a 2003 University of Arizona study noting that rock pocket mice with tan-colored fur are often found among light-colored rocks, while those with black fur were found on dark lava flows. Those researchers identified the genetic basis of this adaptive trait by targeting genes for further study that were known to be involved in pigmentation, and showed that gene variants were, indeed, associated with the different habitats.
“For our study, we reversed the order, beginning with genes that showed evidence of selection, and then looking at the environmental factors that might influence those genes,” said Taylor, who emphasized that the research was a collaboration that included fellow Berkeley professors Louise Glass and Rachel Brem, plus a host of graduate students.
The study argued that this “reverse-adaptation” approach is especially useful when studying microbes. “Microbes are inconspicuous by nature and, unlike mice, which can have different colored coats, different strains and species look pretty much the same,” said study lead author Christopher Ellison, a PMB graduate student.
As if to demonstrate this point, the research team discovered that what had been considered a single group of interrelated strains of microbes was instead two distinct populations. “Given that the two populations are structurally indistinguishable, and that they mate with each other, we never could have guessed that they were genetically distinct without having sequenced them,” Taylor said.
With the new cheap and fast methods of censusing microbes, bacteria, or fungi, Taylor said soil and air can be sequenced every few years to see if the populations of microbes are changing. Additionally, researchers said the relative ease of studying a microbe like Neurospora crassa in the lab may make it an appealing tool to monitor the impact of environmental stress.
“If temperature is a key adaptive factor in populations of fungi and microbes in general, this could have important implications in the study of climate change,” said Ellison. “Adaptation is a crucial part of evolution, so microbes could be used to monitor global temperature change.”