But the newly identified mutation inactivates the AtATR protein, so cells don’t respond to DNA damage by shutting down cell division, thereby bypassing that checkpoint, Larsen says. “The plant is effectively blind to what’s happening in the cell.” So the mutant plants can maintain high levels of growth in the presence of toxic levels of aluminum, even if they sustain some DNA damage.
It is not yet clear how much DNA damage the plants sustain, Larsen says. But the strategy could work to promote short-term growth even if it would sacrifice the plants’ DNA. To avoid DNA damage accumulating over generations of growing on aluminum-rich soils, farmers could obtain seeds from mutant plants grown on aluminum-free soil. This would mirror how farmers in industrialized countries use hybrid seeds from agribusinesses rather than saving their own seeds for planting further generations of crops.
“The work provides the first compelling evidence for a mechanism that explains the toxic effect of [aluminum] on root growth,” says plant biologist Manny Delhaize of the Commonwealth Scientific and Industrial Research Organisation Plant Industry Center, in Canberra, Australia. “There have been numerous theories about how aluminum arrests root growth, and this work provides convincing evidence regarding the molecular process involved.” Delhaize says that another method of keeping the growth rates high, while limiting any DNA damage, might be to engineer plants so that their root tips express molecules that would inactivate AtATR.
However, such a targeted approach may not be necessary, Larsen argues. Even after growing the mutant plants on aluminum-containing soils for several generations, there are “no obvious deleterious effects on growth, viability, [or] seed production,” he says.