Bacterial pathogens, such as those causing rice bacterial blight, tomato bacterial wilt, and kiwifruit bacterial canker, pose significant threats to global agriculture. However, effective pesticides to control these diseases are scarce, with copper-based bactericides and antibiotics offering limited efficacy and posing environmental risks.
Chinese scientists have recently made a breakthrough in this area, however, by showing that a widespread plant defense metabolite may help combat bacterial diseases in crops. The metabolite, erucamide, inhibits the virulence of pathogenic bacteria by specifically targeting the Type III Secretion (T3SS) injectisome assembly—a needle-like molecular machine used by Gram-negative bacteria to inject effector proteins directly into host cells.
The research was led by Prof. ZHOU Jianmin's team at the Institute of Genetics and Developmental Biology of the Chinese Academy of Sciences, in collaboration with Prof. LEI Xiaoguang's group at Peking University. The study was published in
Science on February 28.
The researchers determined that erucamide, an ancient and broad-spectrum plant defense metabolite, inhibits T3SS activity in various bacterial pathogens. Genetic analysis demonstrated that plants with elevated erucamide levels exhibit enhanced resistance to bacterial pathogens, whereas those with reduced levels show decreased resistance. These results indicate that erucamide plays a crucial role in plant immunity against bacteria.
Through a combination of advanced techniques—including electron microscopy, biochemical assays, protein structure prediction, molecular docking, and molecular dynamics simulations—the researchers demonstrated that erucamide binds to HrcC, a conserved component of T3SS. This interaction disrupts the assembly of the T3SS injectisome, a structure used by bacteria to inject toxins into host cells.
Remarkably, the binding pocket for erucamide in HrcC is highly conserved across diverse bacterial species, suggesting that this mechanism could have broad-spectrum applicability.
Additionally, the researchers showed that exogenous application of erucamide could protect crops from bacterial diseases, highlighting its potential as a biopesticide for sustainable agriculture.
This study provides important insights into plant immunity and paves the way for developing new, environmentally friendly antibacterial agents, as well as molecular breeding strategies for bacterial disease-resistant crops.
The research was supported by the National Key Research and Development Program of China, the National Natural Science Foundation of China, etc.
Model for the erucamide-mediated disruption of T3SS injectisome assembly in the bacterial pathogen. (Image by IGDB)
