Nav: Home

Overspending on defense arsenal bankrupts a plant's economy

October 22, 2018

Defend or grow? Can plants do both at the same time? Michigan State University scientists might be inching closer to answering these questions. The answers matter. They could someday help us understand natural ecosystems or help farmers increase yields, without increasing dependence on chemicals to resist pests.

The lab of Gregg Howe at the MSU-DOE Plant Research Laboratory has genetically tuned a plant to become highly resistant to insect attacks. But becoming such a fortress compromises its growth and procreative capabilities. The research is published in Proceedings of the National Academy of Sciences.

The findings seem to support a long-held paradigm called the growth-defense trade-off. It goes something like this: plants work with a fixed energy budget. So, they prioritize resource usage depending on need. If they spend more energy on growth, their defenses are compromised. On the other hand, having more defense capabilities penalizes growth.

Plants, in nature, seem to follow this general rule. When stressed by drought, disease, or insect pests, plants will mount defensive responses, which typically slows growth to a crawl. But if plants have to grow fast, for example to compete with neighbors for light, their defenses are weakened.

"Our study provides evidence that large investments in defense necessarily reduce the amount of resources that otherwise would be available for growth and reproductive fitness," says Qiang Guo, a graduate student in the Howe lab.

The study focuses on the defense system against herbivores, which depend on plants for shelter and food. If a caterpillar starts munching on a leaf, the system produces toxins that ward it off. But in the absence of danger, the plant shuts down its defense system with a battery of 13 repressor proteins, called JAZ, that put the brakes on defense in order to save energy.

A former post-doc in the Howe lab, Yuki Yoshida, genetically bred a plant missing 10 of these 13 repressor proteins. The result was a plant in continuous, overdrive defense mode.

"It kept producing defense compounds, even in the absence of threats. As expected, it showed high resistance to insects," says Guo. "Unleashing this defense arsenal also provided protection against fungi that target plant tissues."

Plants must balance their budgets too


Alas, there are dire consequences to a strong plant without.... "All that JAZ."

"They have a much slower growth rate compared to their wild type counterparts. We can literally see and measure the deficit in growth rate per day."

The plants also have strongly compromised reproductive success. They produce 1/3rd fewer seeds, and those seeds germinate later than usual. The seeds tend to be smaller and of lower quality, packed with less nutritional fats and with a different lipid make-up.

The team ruled out that photosynthesis - which is how plants obtain energy resources - was compromised. Enter Ian Major, a post-doc in the Howe lab.

"The mutated plant gets the same amount of energy compounds from photosynthesis as its wild, natural counterpart," Major says. "However, it consumes more energy than usual. We think the plant is fueling the massive and constant production of defense compounds, which draws resources away from growth.

Guo adds that the high-energy usage starves the plants of nutrients. "It doesn't have enough energy to perform other functions optimally, like growth" he adds. "To illustrate that point, we fed the plant with sugar, a fuel source, and it partially recovered its growth."

"Our conclusion is that JAZ proteins help plants grow and reproduce by taming their defenses when the threat of attack is low, which conserves energy. Depending on the severity of the threat, the JAZ proteins will dial up the defenses as needed, perhaps like a dimmable light switch, ," Major says.

The research team highlights the importance of Dr. Yoshida's ten-year effort to knock out the JAZ proteins, one by one. "He ignored a lot of us when we told him it was a high-risk, difficult project. But now, we have new ways of thinking about plants and how we can combine plant traits in new and useful ways," Major says.
-end-
This work was funded by the Department of Energy's Office of Basic Energy Sciences - Physical Biosciences program.

DOE/US Department of Energy

Related Plants Articles:

How do plants forget?
The study now published in Nature Cell Biology reveals more information on the capacity of plants, identified as 'epigenetic memory,' which allows recording important information to, for example, remember prolonged cold in the winter to ensure they flower at the right time during the spring.
The revolt of the plants: The arctic melts when plants stop breathing
A joint research team from POSTECH and the University of Zurich identifies a physiologic mechanism in vegetation as cause for Artic warming.
How plants forget
New work published in Nature Cell Biology from an international team led by Dr.
Ordering in? Plants are way ahead of you
Dissolved carbon in soil can quench plants' ability to communicate with soil microbes, allowing plants to fine-tune their relationships with symbionts.
When good plants go bad
Conventional wisdom suggests that only introduced species can be considered invasive and that indigenous plant life cannot be classified as such because they belong within their native range.
How plants handle stress
Plants get stressed too. Drought or too much salt disrupt their physiology.
Can plants tell us something about longevity?
The oldest living organism on Earth is a plant, Methuselah a bristlecone pine (Pinus longaeva) (pictured below) that is over 5,000 years old.
Plants might be helping each other more than thought
Contrary to the long-held belief that plants in the natural world are always in competition, new research has found that in harsh environments mature plants help smaller ones -- and thrive as a result.
Not all plants are good for you
A new scientific review highlights a significant global health issue related to plants that sicken or kill undernourished people around the world, including those who depend upon these plants for sustenance.
How plants react to fungi
Using special receptors, plants recognize when they are at risk of fungal infection.
More Plants News and Plants Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Listen Again: The Biology Of Sex
Original broadcast date: May 8, 2020. Many of us were taught biological sex is a question of female or male, XX or XY ... but it's far more complicated. This hour, TED speakers explore what determines our sex. Guests on the show include artist Emily Quinn, journalist Molly Webster, neuroscientist Lisa Mosconi, and structural biologist Karissa Sanbonmatsu.
Now Playing: Science for the People

#569 Facing Fear
What do you fear? I mean really fear? Well, ok, maybe right now that's tough. We're living in a new age and definition of fear. But what do we do about it? Eva Holland has faced her fears, including trauma and phobia. She lived to tell the tale and write a book: "Nerve: Adventures in the Science of Fear".
Now Playing: Radiolab

The Wubi Effect
When we think of China today, we think of a technological superpower. From Huweai and 5G to TikTok and viral social media, China is stride for stride with the United States in the world of computing. However, China's technological renaissance almost didn't happen. And for one very basic reason: The Chinese language, with its 70,000 plus characters, couldn't fit on a keyboard.  Today, we tell the story of Professor Wang Yongmin, a hard headed computer programmer who solved this puzzle and laid the foundation for the China we know today. This episode was reported and produced by Simon Adler with reporting assistance from Yang Yang. Special thanks to Martin Howard. You can view his renowned collection of typewriters at: antiquetypewriters.com Support Radiolab today at Radiolab.org/donate.