Plants, like many other organisms, have circadian clocks that help them anticipate various environmental and biological events that occur at precise times of the day. Processes like photosynthesis, fragrance emission and time of bloom are all regulated by this timekeeping mechanism.

Now, researchers report in the journal Nature that genes in certain plants fend off infections with the help of the clock as well.

Twenty-two genes in the plant Arabidopsis, all connected to the plant’s ability to resist infection, were expressed only from the evening onward, peaking at dawn.

The timing corresponds with the formation of spores in a funguslike pathogen that attacks the plant and results in a condition known as downy mildew disease. The disease weakens the plant and forms an unsavory coating of fuzzy mildew.