Professor Cyril Zipfel from The Sainsbury Laboratory said that a major dilemma faced by plants is whether to invest their energy in growth or defending against pathogens.
He said that knowing how this is controlled adds a powerful tool in their ability to breed disease resistant plants with maximum yield.
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.
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 findings have been published in the open-access scientific journal eLife.