US scientists in plant defence breakthrough

Scientists in Texas examining the effects of certain molecules on promoting plant growth and boosting natural protection have made a breakthrough. The scientists at the University of Texas, Arlington, working with colleagues in Michigan investigating the hormone jasmonate, have come a step closer to understanding how it affects defence and growth.

The scientists revealed how a 'transcriptional repressor' of the jasmonate signalling pathway affects the use to which jasmonates, hormones with roles in both reproductive development and plant growth, are put within the plant cells.

The hormonal jasmonate signalling is thought to maintain a balance between plant growth and defence. When stressors such as herbivorous insects, pathogens, or drought affect the plant, jasmonate signalling shifts the plant's cellular processes into defence mode.

The researchers said their discovery may eventually help farmers to achieve better crop yields with less use of harmful chemicals. They focused on the role of jasmonate signalling repressors referred to as JAZ, specifically how JAZ interacts with certain processes and proteins within the plant's cells which impact on growth.

Biology professor and study author Maeli Melotto commented, "This is a small piece of a bigger picture, but it is a very important piece.”

Co-author and Michigan State University professor Sheng Yang He elaborated, that the process "May be important because activation of jasmonate signalling, although important for plant defence against pathogens and insects, is energy-consuming and could lead to growth inhibition – a widely known phenomenon called growth-defense tradeoff. In other words, plants have developed a mechanism to tightly repress [their] defence responses until they become necessary, for example during pathogen and insect attacks."

Professor Melotto said understanding jasmonate signaling at the molecular level is also vital because some plant pathogens have developed ways to mimic the hormone's action in the cell. This gives them the ability to aggressively colonise plants without activating natural defence mechanisms. She said the next step in her jasmonate research is to determine which area of the JAZ protein is responsible for plant innate immunity.

The Texas-based biology professor added, "This is one way to have sustainable agriculture, by increasing genetic resistance we could reduce the use of pesticides, decrease crop production costs and promote environmentally friendly farming practices."