By Olivia Solon, Wired UK
Biologists at Rice University have discovered that while plants might look fairly inactive in the day, they are surreptitiously preparing for battle with hungry insects.
"When you walk past plants, they don't look like they're doing anything," said Janet Braam, one of the investigators on a new study, which appears in the Proceedings of the National Academy of Sciences. "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."
Biologists have long known that plants have an internal clock that lets them measure the passing of time regardless of the light conditions. Some plants move their leaves to follow the Sun during the day but then "reset" their leaves at night and move them back toward the east in anticipation of the sunrise. Recent studies have been applying genetic tools to study plant circadian rhythms. Researchers have discovered that as many as a third of genes in the Arabidopsis thaliana plant (also known as thale cress or mouse cress) are activated by their circadian cycle. Some of the circadian-regulated genes are linked to wounding or healing responses, meaning that they can anticipate an attack from insects just as they anticipate the sunrise.
In order to test this theory, graduate biochemistry and cell biology student Danielle Goodspeed designed an experiment. She used 12-hour light cycles to regulate the circadian clocks of the Arabidopsis plants and some cabbage looper caterpillars, which like to munch on the plants. Half of the plants were placed with caterpillars on a regular day-night cycle and the other half were placed with 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," said Goodspeed.
Goodspeed and colleagues including Wassim Chehab found that the plant uses its circadian clock to increase the production of a hormone jasmonate – which plants use to regulate the production of metabolites that interfere with insect digestion – during the day, when greedy insects most tend to feed. They also discovered that the circadian clock was used to regulate the production of other chemical defences such as those that protect against bacterial infections.
The findings could help inform new strategies for insect resistance.
You can read the full paper here.
Video: RiceUniversity/YouTube
Source: Wired.co.uk
