Plants use circadian rhythms to prepare for battle with insects

Feb 13, 2012
Rice University biologists found that plants with altered circadian clocks were unable to defend themselves against leaf-eating cabbage looper caterpillars. Credit: Tommy LaVergne/Rice University

In a study of the molecular underpinnings of plants' pest resistance, Rice University biologists have shown that plants both anticipate daytime raids by hungry insects and make sophisticated preparations to fend them off.

"When you walk past plants, they don't look like they're doing anything," said Janet Braam, an investigator on the new study, which appears this week in the . "It's intriguing to see all of this activity down at the genetic level. It's like watching a besieged fortress go on full alert."

Braam, professor and chair of Rice's Department of Biochemistry and Cell Biology, said scientists have long known that plants have an that allows them to measure time regardless of light conditions. For example, some plants that track the sun with their leaves during the day are known to "reset" their leaves at night and move them back toward the east in anticipation of sunrise.

This video is not supported by your browser at this time.

In recent years, scientists have begun to apply powerful to the study of plant circadian rhythms. Researchers have found that as many as one-third of the genes in -- a widely studied species in -- are activated by the . Rice biochemist Michael Covington found that some of these circadian-regulated genes were also connected to wounding responses.

"We wondered whether some of these circadian-regulated genes might allow plants to anticipate attacks from insects, in much the same way that they anticipate the sunrise," said Covington, now at the University of California, Davis.

Danielle Goodspeed, a graduate student in biochemistry and cell biology, designed a clever experiment to answer the question. She used 12-hour to entrain the circadian clocks of both Arabidopsis plants and cabbage loopers, a type of caterpillar that eats Arabidopsis. Half of the plants were placed with caterpillars on a regular day-night cycle, and the other half were placed with "out-of-phase" caterpillars whose internal clocks were set to daytime mode during the hours that the plants were in nighttime mode.

"We found that the plants whose clocks were in phase with the insects were relatively resistant, whereas the plants whose clocks were out of phase were decimated by the insects feeding on them," Goodspeed said.

Wassim Chehab, a Rice faculty fellow in biochemistry and cell biology, helped Goodspeed design a follow-up experiment to understand how plants used their internal clocks to resist insect attacks. Chehab and Goodspeed examined the accumulation of the hormone jasmonate, which plants use to regulate the production of metabolites that interfere with insect digestion.

They found that Arabidopsis uses its to increase jasmonate production during the day, when insects like cabbage loopers feed the most. They also found that the plants used their internal clocks to regulate the production of other chemical defenses, including those that protect against bacterial infections.

"Jasmonate defenses are employed by virtually all plants, including tomatoes, rice and corn," Chehab said. "Understanding how plants regulate these hormones could be important for understanding why some pests are more damaging than others, and it could help suggest new strategies for insect resistance."

Explore further: Scientists throw light on the mechanism of plants' ticking clock

More information: www.pnas.org/content/early/201… /1116368109.abstract

Related Stories

Circadian clock controls plant growth hormone

Aug 13, 2007

The plant growth hormone auxin is controlled by circadian rhythms within the plant, UC Davis researchers have found. The discovery explains how plants can time their growth to take advantage of resources such ...

Plant clock gene also works in human cells

Dec 01, 2010

A gene that controls part of the 'tick tock' in a plant's circadian clock has been identified by UC Davis researchers. And not only is the plant gene very similar to one in humans, but the human gene can work in plant cells ...

Recommended for you

Researchers uncover secrets of internal cell fine-tuning

5 hours ago

New research from scientists at the University of Kent has shown for the first time how the structures inside cells are regulated – a breakthrough that could have a major impact on cancer therapy development.

Microscopic rowing—without a cox

6 hours ago

Many different types of cell, including sperm, bacteria and algae, propel themselves using whip-like appendages known as flagella. These protrusions, about one-hundredth of a millimetre long, function like ...

Illuminating the dark side of the genome

12 hours ago

Almost 50 percent of our genome is made up of highly repetitive DNA, which makes it very difficult to be analysed. In fact, repeats are discarded in most genome-wide studies and thus, insights into this part ...

User comments : 4

Adjust slider to filter visible comments by rank

Display comments: newest first

Ed_Hughes
1 / 5 (1) Feb 18, 2012
So do we infect plants prior to harvesting to improve our food source.
or
Do we harvest plants while they sleep to improve our food source.
Then
Do we freeze the plant product the instant it is harvested to freeze its content. Avoiding plant death reaction defenses.
Ed_Hughes
1 / 5 (1) Feb 18, 2012
Very hard to study.
If it like animal meat you have to kill the animal very fast and remove all organs to prevent various circulatory systems from affecting the harvest. Then for taste age or freeze the products to preserve food quality.
Kill the apple in the middle of the night when it is sleeping at the time of harvest to improve its food value.
kaasinees
1 / 5 (1) Feb 18, 2012
And what makes you think the apple is sleeping during the night?
Ed_Hughes
1 / 5 (1) Feb 18, 2012
The artical stated plants reset for a morning cycle. I don't mean to be stupid. I mean to help create a better food source for us.