Plant growth vs defence: new discovery could support improved yields

Plants take in and synthesise protective hormones to safeguard themselves against infection from pathogens, but it has long been accepted that excessive accumulation of such hormones can significantly impede growth.

Now a research team from Kumamoto University in Japan has made a significant breakthrough, by identifying a new mechanism that controls the balance between a plant’s hormonal defences and growth, which could lead to improved crop yields.

A plant’s growth is known to be inhibited following pathogen attack, because more of its energy is used for the synthesis of defence hormones such as salicylic acid and lignin. Therefore, the plant needs to ensure a safe balance to keep it adequately defended and able to grow uninhibited.

Previously, balance regulating mechanisms had only been observed in a plant’s leaves, but the team behind the new research has now demonstrated that a gene known as DEL1 plays a crucial role in helping to balance growth and defence in plant roots.

The researchers infected a DEL1-deficient plant with the parasitic roundworm Meloidogyne incognita, which is known to affect a plant’s roots. Following infection, the DEL1-deficient plants showed excessive salicylic acid and lignin accumulation, as well as significant root growth inhibition and overall higher resistance to infection than non-DEL1-deficient types of the same plant. The findings therefore suggested DEL1 plays a role in suppressing a plant’s defence mechanism.

Study leader Professor Shinichiro Sawa said the research demonstrates that controlling genes such as DEL1 could allow for the development of plants that are more pest resistant and will offer a better yield.