An international team of researchers led by scientists at the Sainsbury Laboratory in Norwich, UK, has succeeded in transferring broad spectrum resistance to some important plant diseases into different plant families. They say this provides a new way to produce crops with long-term resistance to economically important diseases.
Breeding programmes for resistance generally rely on single resistance genes that recognise molecules specific to particular strain of pathogen. As a result this kind of resistance is usually specific to particular plants and is often rapidly overcome by the pathogen evolving to avoid recognition.
However, plants have another natural defence system, based on pattern recognition receptors (PRRs), which recognise molecules that are essential for pathogen survival. These are less likely to mutate, because doing so would threaten a pathogen’s survival, making resistance to them more durable.
In addition, these essential molecules are common to many different microbes, meaning that if a plant recognises and can defend itself against one of these molecular patterns, it is likely to be resistant against a broad range of other pathogens.
Very few of these PRRs have been identified to date. Cyril Zipfel and his group at the Sainsbury Laboratory, took a Brassica-specific PRR that recognises bacteria, and transformed it into the Solanaceae plants Nicotania benthaminia and tomato.
We hypothesised that adding new recognition receptors to the host arsenal could lead to enhanced resistance, said Zipfel.
These transformed plants have been tested against a variety of different plant pathogens and found drastically enhanced resistance against many different bacteria, including some significant pests such as Rastonia solanaceraum, which causes bacterial wilt.
“The strength of this resistance is because it has come from a different plant family, which the pathogen has not had any chance to adapt to. Through genetic modification, we can now transfer this resistance across plant species boundaries in a way traditional breeding cannot,” said Zipfel.
The finding, that plant recognition receptors can be successfully transferred from one plant family to another provides a approaching to engineering disease resistance. The Zipfel group is currently extending this work to other crops including potato, apple, cassava and banana that all suffer from important bacterial diseases, particularly in the developing world.
A guiding principle in plant pathology is that most plants tend to be resistant to most pathogens. [This] work indicates that transfer of genes that contribute to this basic innate immunity from one plant to another can enhance pathogen resistance,” said Sophien Kamoun, Head of the Sainsbury Lab. “The implications for engineering crop plants with enhanced resistance to infectious diseases are very promising.”
The research was funded by two charities, the Gatsby Charitable Foundation and the Two Blades Foundation, which have patented the technology on behalf of the inventors. The research involved research groups from INRA/CNRS in France, the University of California, Berkeley and Wageningen University in the Netherlands.