Plants Use Hormones to Choose Growth Over Pathogen Defense

New insights into how plants use steroid hormones reveal that the organisms are able to actively devote their energy to growth instead of defending themselves against pathogens.

Writing in the open-access journal eLife, the researchers suggest that the information could be used to engineer crops that combine size with pathogen resistance.

"A major dilemma faced by plants is whether to invest their energy in growth or defending against pathogens," said professor Cyril Zipfel from The Sainsbury Laboratory.

"Knowing how this is controlled adds a powerful tool in our ability to breed disease resistant plants with maximum yield," Zipfel said.

Zipfel and his colleagues examined the protein BZR1 in plants. They found that the protein is responsible for rapidly tipping the balance in favor of growth over defense of pathogen attacks. Doing so can be especially beneficial for a plant when it is still a seed germinating in soil.

"Light is essential for plant's survival and the number one priority for a seedling is to reach sunlight," said The Sainsbury Laboratory's Rosa Lozano-Durán, first author of the study.

"Investing the limited resources in fighting back a pathogen could have lethal consequences," Lozano-Durán said.

The researchers learned that BZR1 controls the activity of genes related to immunity, and that it is involved in growth mediated by a common plant steroid hormone known as a brassinosteroid.

"Brassinosteroids are already the focus of studies to breed semi-dwarfed cereal crops. The current study shows that reducing their levels or their activity could have the added benefit of making crops better able to resist disease," the researchers said in a statement.