Damage control: Plants juggle genome maintenance and growth by being organized

In a study published in Science Advances, a research team led by Nara Institute of Science and Technology has revealed that plants use combined control of the plant hormones cytokinin and auxin to organize DNA damage responses while maintaining growth.

Plants are highly adaptable organisms that never stop growing, thanks largely to the functions carried out by their roots. Because of the essential role that roots play in plant growth, root development is highly responsive to fluctuating conditions underground, including environmental stresses. These stresses tend to limit root growth, and can damage DNA.

"Plants actively respond to DNA damage, and these responses are controlled by the cell cycle checkpoint mechanism," says project leader Masaaki Umeda. "The cell cycle is stopped at a certain stage so that DNA can be repaired, or in extreme cases, cell death initiated. What we wanted to know was how the DNA damage responses are organized to allow continuous root growth."

Unlike animal cells, plant cells aren't mobile, so plants can't replace dead cells with surrounding living cells. To simultaneously maintain their genomes and allow organ development, plants initiate different DNA damage responses that are dependent on the different types of cells in tissues.

"We found that the combined control of two plant hormones, cytokinin and auxin, organizes different DNA damage responses at the cost of minimized cell death," explains first author Naoki Takahashi. "This is a sophisticated way to retain stem cells while maintaining their genomes in damaged plants."

A decrease in auxin triggers stem cell death and stops the cell cycle at the G2 phase, while increased cytokinin signals support early endoreplication -- a cell cycle variant where the genome is duplicated without cell division.

The study explains previously unidentified mechanisms of keeping genomes stable in a developmental setting, which allow continuous organ growth in fluctuating environments. The results of this study will have wide-ranging applications to research on agricultural technologies, particularly for plant growth and development in extreme environments. Future studies will illuminate how plants develop organs beyond the embryonic stage via the maintenance of genome stability in changing conditions.