Adaptation-triggering technique could radically alter agriculture
When you think you’ve got it rough, consider the lilies—and the other plants that are firmly rooted, stuck in place.
Because they can’t run away from stress, plants have to adapt to get through whatever misfortune happens to come their way.
Scientists have observed this adaptation in plants, that once they have weathered a particular stress, they are more readily able to mount their defense to a subsequent instance of that stress. In this respect, plants appear to have a short-term memory.
Penn State’s Sally Mackenzie and other like- minded scientists have taken this idea a step further by hypothesizing that plants may be able to distinguish between short-term and chronic stress, and that they may also be capable of passing their adaptations to chronic stresses on to their offspring. In other words, plants may even possess an intergenerational, “long-term” memory.
“People have speculated on this for a long time,” Mackenzie said. “In my lab, there are four things that we’re interested in. First of all, whether it’s true and we can create it in the laboratory—a long-term memory. Two, can we figure out the signals that actually condition long-term memory? Are they chronic stress signals? Three, can we understand the epigenetic phenomena—the non- genetic changes—that happen in an organism to make that memory happen? Four, can we exploit it, particularly for agricultural purposes? Can we derive more from our current varieties by being able to exploit that epigenetic potential that we haven’t been able to realize before?”
Mackenzie sees, potentially, two big gains from that ability—namely, to increase yield and improve resilience—and toward those ends, she and her lab have developed a novel system that allows them to trigger specific adaptations in a plant’s epigenome by manipulating the expression of a stress-response gene that is present in all plants.
“They hold onto that adaptation indefinitely,” she explained. “And that plant now becomes the start of a new breeding line, because it’s reprogrammed its epigenetic information—its epigenome, if you will— in such a way that it has heightened responsiveness to stress.”
When that plant is crossed to a genetically identical, unmodified line—a so-called “sister” plant—their offspring display improved qualities that supersede those of the parents.
“It turns out that, in subsequent generations, we see enhanced growth potential,” she said. “We see more resiliency—heightened abiotic stress tolerance, heat tolerance, cold tolerance, drought tolerance.”
Mackenzie explains that because those qualities are passed epigenetically, they’re also graft- transmissible—so cuttings from existing varieties could be grafted to rootstock from the modified mother plant in order to produce heritable change in any resulting seed.
But perhaps the most interesting thing, she said, is that, because they haven’t actually altered the plant’s genetics, it’s not considered to be a transgenic or genetically modi ed organism (GMO)—and so it’s not subject to the additional regulations imposed on such crops.
“We can deploy this new crop agriculturally with no issues with regard to regulatory constraints,” she said. “Companies that have already got the perfect variety, we can make it a perfect-plus. And we can do this in any crop.”
Mackenzie and her lab are already collaborating with a startup called Epicrop Technologies, using this system to breed epigenetics into crops to enhance their overall value and productivity.
“I could envision that this could come out, in some varieties, perhaps in the next ve years,” she said. “We are now entering a time, particularly with climate change, where it behooves all of us who are plant scientists to think very carefully about the implications of our work. Our hope is to grow this company into something that will have real-world impact. And Penn State is a great place to do that— we have everything you need to make that kind of an impact, internationally and domestically, with the research we do here.”
Sally Mackenzie is the Lloyd and Dottie Huck Chair for Functional Genomics and a professor of biology and plant science at Penn State.