Fix, not fight: Scientists help plants regenerate after injury

Date:
February 10, 2022
Source:
New York University
Summary:
After injury, plants make a trade-off between repairing
damaged tissue and ramping up their defenses, according to a new
study. Understanding how plants regulate these responses enabled
the researchers to nudge wounded plants toward repair instead of
defense, a strategy that could be useful in improving regeneration
in important staple crops like corn.



FULL STORY ========================================================================== After injury, plants make a trade-off between repairing damaged tissue and ramping up their defenses, according to a new study led by researchers
in New York University's Center for Genomics and Systems Biology and
published in Developmental Cell.


========================================================================== Understanding how plants regulate these responses enabled the researchers
to nudge wounded plants toward repair instead of defense, a strategy
that could be useful in improving regeneration in important staple crops
like corn.

Under attack? Plants "fight or fix" Plants are subject to a wide array
of attacks and injuries, from caterpillars and rabbits munching on their
leaves to grubs or fungi attacking their roots.

"Plants can hardly go a few days without some kind of injury. As a result,
they have developed sophisticated strategies to respond," said Kenneth Birnbaum, a professor in NYU's Department of Biology and Center for
Genomics and Systems Biology and the study's senior author.

Unlike animals, who employ "fight or flight" responses when attacked,
plants can't run. Instead, injury triggers a "fight or fix" response
in plants, prompting them to either regenerate their damaged or missing
parts or defend themselves. Plants defend themselves by rapidly producing compounds designed to stop an animal or pathogen from further attacks
(these secondary compounds have proven to be particularly useful in
medicine, giving us drugs like morphine, paclitaxel, and colchicine).



==========================================================================
The trade-off between defense and regeneration This study sought to
understand how the "fight or fix" responses are linked - - whether they
are activated together and ramp up at the same time, or if there is
a trade-off, with one response increasing as the other decreases. The researchers studied Arabidopsis, a small plant widely used as a model
organism in plant biology, and corn, America's largest crop and a
critically important source of food for people and animals.

After cutting off tips of the roots and other parts of the plants
to injure them, the researchers observed that plants produce some
regeneration response and some defense response, but do not ramp both
to maximal capacity -- and in fact, lowering one response increases
the other.

"The 'fight or fix' responses seem to be connected, like a seesaw or
scales - - if one goes up, the other goes down. Plants are essentially
hedging their bets after an attack," said Marcela Herna'ndez Coronado of Cinvestav in Mexico, the study's first author and a former postdoctoral researcher at NYU.

The researchers found that this balance in regeneration and
defense responses was regulated by plant glutamate receptor-like
(GLRs) proteins, which are distant relatives to glutamate receptors
found in the brain. This allowed them to use drugs typically used in neurobiology research to study the plant's responses to injury. GLRs have
been implicated in plant defense responses, but in the study, GLRs also
played a role in regeneration after injury, with GLR- mediated signals
dialing down the regeneration system and turning up the defense response.



========================================================================== Targeting glutamate receptors to boost regeneration Knowing that GLRs
regulate both regeneration and defense responses presents an opportunity
to improve crop growth -- especially cereal crops like corn, sorghum,
and wheat, which are particularly resistant to regeneration.

"These glutamate receptors provide a 'druggable target' that we can use
to enhance plant regeneration and propagation," said Birnbaum.

The researchers targeted GLRs by inhibiting the receptors' activity
through two means: genetics and drugs. The genetic research, aided
by Jose' Feijo' and his lab at the University of Maryland, involved
comparing the injury responses of normal plants with "quadruple mutants"
-- plants with mutations in four of the genes involved with GLRs. The researchers found that the quadruple mutants were better at regeneration,
which suggests that the mutations compromised the defense response,
and in doing so enhanced the regeneration response.

The researchers also used three neuronal antagonists to inhibit GLR
activity.

The three drugs each blocked GLR-mediated signaling after plant
injury, which altered the plants' decision-making process to favor regeneration. This dramatically enhanced regeneration, even more so than
in the quadruple mutants.

"Retuning the balance between plant defense and regeneration could be used
to improve regeneration for biotechnology, conservation, and propagation
of staple food crops," said Birnbaum. "Breeding crops that more readily regenerate and can adapt to new environments is critical in the face
of climate change and food insecurity." The research is supported
by the National Institutes of Health (R35GM136362, R01-GM131043) and
the National Science Foundation (1934388, MCB-1930165). In addition to Birnbaum, Herna'ndez Coronado, and Feijo', study authors include Poliana Coqueiro Dias Araujo, Pui-Leng Ip, and Ramin Rahni of NYU and Custo'dio
Nunes, Michael Wudick, and Michael Lizzio of the University of Maryland.

========================================================================== Story Source: Materials provided by New_York_University. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Marcela Herna'ndez-Coronado, Poliana Coqueiro Dias Araujo,
Pui-Leng Ip,
Custo'dio O. Nunes, Ramin Rahni, Michael M. Wudick, Michael
A. Lizzio, Jose' A. Feijo', Kenneth D. Birnbaum. Plant glutamate
receptors mediate a bet-hedging strategy between regeneration and
defense. Developmental Cell, 2022; DOI: 10.1016/j.devcel.2022.01.013 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/02/220210113241.htm

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