New York University researchers have provided more insights in a new study on the response of plants when under attack while also demonstrating how they can be aided to recover from injuries.
Humans are known to exhibit a “fight or flight” response when in a threatening situation. We either confront the danger or run away.
On their part, however, plants are static. They are not able to change position when they are being attacked by animals or pathogens. Scientists say they instead have recourse to a “fight or fix” response, with a trade-off between these choices.
The NYU team was able to help revive injured plants using their knowledge of the injury response. It, thus, highlights a possible tactic that could be employed on a larger scale to promote recovery in key staple crops.
Findings were published in the journal Developmental Cell.
Digging deeper into the responses
When being attacked, plants quickly produce compounds that are intended to stop further attacks by animals or pathogens. A number of these compounds have medical uses for humans – examples include morphine and paclitaxel.
However, repelling attacks is not the only thing that plants must see to. They also have to restore parts damaged by animals or pathogens. Plants have to decide whether it is more important to defend themselves or work on already-injured or missing parts.
Researchers wanted to understand in this study the link between the two responses. They were interested in finding out whether they are triggered concurrently at the same pace or one is increased while the other is decreased at a time.
The team damaged parts and roots of plants (Arabidopsis and corn) by cutting off their tips. Following this, it noticed that plants generated a little defense response and a bit of restorative response.
There was a trade-off between these responses – when one went up, the other lowered. Neither was observed to reach its maximum capacity.
“The ‘fight or fix’ responses seem to be connected, like a seesaw or scales – if one goes up, the other goes down,” said study first author Marcela Hernandez Coronado. “Plants are essentially hedging their bets after an attack.”
Help for regeneration
The scientists further observed that the “fight or fix” responses are regulated by glutamate receptor-like proteins (or GLRs). There has been evidence that these play a part in plant defense responses.
This current study shows that GLRs are also in some way involved in regeneration following an injury to a plant. Signals mediated by these substances dampen repair and fire up the defense.
GLRs are regarded as distant relatives of glutamate receptors present in the brain. As a result, the team was able to use drugs commonly used in neurological research to probe the response of plants to damage.
Exploiting both drugs and genetics, the researchers inhibited the activity of GLRs. They compared regular plants with “quadruple mutants,” which are plants having mutations in four GLR-related genes.
The quadruple mutants showed a better regeneration response. This implies that mutations inhibited the defense response, thereby boosting plants’ ability to regenerate.
“These glutamate receptors provide a ‘druggable target’ that we can use to enhance plant regeneration and propagation,” said senior study author Kenneth Birnbaum, a professor in the Department of Biology at NYU.
The knowledge of the role of GLRs in balancing defense and regeneration responses can prove quite helpful for augmenting the growth of crops that are usually more resistant to regeneration. An example of such is corn, which is a very important crop for both humans and animals in America.
In addition, the team made use of three neuronal antagonists to block GLR activity. This made plants produce more regenerative responses – at an even higher level than that seen in the quadruple mutants.
Birnbaum stated that altering the balance between the corrective response and the defense response could help crops adapt better to changing environments. This may also improve yields to provide more food.