Plants Use Internal Timing for Defense Against Pest

Scientists at Rice University in Texas reported that the plant's circadian clock, acting like hormone signals, helps plants defend themselves from anticipated attack by pests. Danielle Goodspeed and colleagues used 12-hour light cycles to entrain the circadian clocks of Arabidopsis plants and cabbage loopers. One set of plants were exposed to caterpillars on a regular day-night cycles, while another set were placed with "out-of-phase" caterpillars whose biological clocks were set to daytime mode during the hours that the plants were in night time mode. Results showed that the plants with clocks in phase with the insects were relatively resistant, while the other set of plants turned out to be infested by the insects.

They team also examined the accumulation of the hormone jasmonate, which is used by plants in controlling metabolite production to impede insect digestion. They found that the Arabidopsis uses its internal clock to produce more jasmonate during the day, which is the time when insects like cabbage loopers attack plants. They also discovered that the internal clocks control the production of other chemical defenses such as those that protect plants against bacterial infections.

For more details about the study visit http://www.pnas.org/content/early/2012/02/07/1116368109.abstract