An enzyme that suppresses plant immune defences could be the key to engineering Fusarium-resistant crops
The destructive fungal pathogen Fusarium graminearum uses a specialised protein to weaken plant immunity and cause Fusarium head blight (FHB), a study has found.
Published in the journal Molecular Plant-Microbe Interactions, this new insight into how F. graminearum attacks crops could lead to the development of genetically engineered disease-resistant grains.
The collaborative research team, led by Matthew Helm of the U.S. Department of Agriculture–Agricultural Research Service, Roger Innes at Indiana University Bloomington and Kim Hammond-Kosack at Rothamsted Research, identified and functionally characterised a fungal protein called TPP1. This protease enzyme is secreted by F. graminearum during infection and plays a central role in helping the fungus overcome plant defences by targeting the chloroplast—an essential part of the plant cell responsible not only for energy production but also for immune signalling.
“What excites us most is that this effector protease not only promotes disease but also targets the chloroplast, which is an unexpected and strategic location for disarming the plant’s immune system,” said Dr Helm. “This study could be transformational for developing disease-resistant crops.”
FHB continues to threaten global food security, causing significant yield losses and contaminating grain with mycotoxins that are harmful to humans and livestock. In this study, researchers showed that when the gene for TPP1 was knocked out, the fungus became significantly less virulent, confirming that this protein is essential for infection. The finding sheds light on a largely unexplored mechanism in fungal pathogenesis.
This is the first report to identify an effector protease from F. graminearum that targets the chloroplast and directly contributes to disease development by suppressing plant immune responses. The discovery of TPP1’s role marks a significant advancement in our understanding of fungal pathogenesis. It also opens up exciting possibilities for using ‘decoy’ engineering strategies to develop wheat and barley varieties with built-in resistance.
“In addition, TPP1 appears to be highly conserved across a broad group of fungal pathogens, making it potentially a prime target to deliver plant disease resistance against other problematic fungal species,” added Rothamsted’s Dr. Hammond-Kosack.
With implications for both the plant-microbe and broader host-microbe research fields, this foundational work lays the groundwork for bioengineering more resilient wheat and barley varieties, which is an urgent need in the face of a changing climate and rising global food demand. The ultimate goal, say the authors, is to protect global food supplies by reducing crop losses from FHB which makes this study is an important step forward.
