Plants use hormones to choose growth over pathogen defence

London: Scientists have discovered how plants use steroid hormones to choose growth over defending themselves against pathogens. The findings could be used to engineer crops that combine size with pathogen resistance, researchers said. "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, UK.

"Knowing how this is controlled adds a powerful tool in our ability to breed disease resistant plants with maximum yield," Zipfel said. A key protein, BZR1, is responsible for rapidly tipping the balance in favour of growth and ignoring pathogen attack when it is a matter of life and death. This is the case when a seed germinates in the soil, for example. "Light is essential for plant`s survival and the number one priority for a seedling is to reach sunlight," said Dr Rosa Lozano-Duran, first author of the study from TSL. "Investing the limited resources in fighting back a pathogen could have lethal consequences," Lozano-Duran said. The protein identified controls the activity of genes related to immunity. It is involved in growth mediated by steroid hormones called brassinosteroids, which are common to all plants. 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, researchers said. The study is published in the journal eLife.