Chitin triggers tissue-specific immunity in wheat associated with Fusarium head blight

Authors: Hao, Guixia; Tiley, Helene; McCormick, Susan

Submitted to: Frontiers in Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/13/2022
Publication Date: 2/9/2022
Citation: Hao, G., Tiley, H., McCormick, S. 2022. Chitin triggers tissue-specific immunity in wheat associated with Fusarium head blight. Frontiers in Plant Science. 13. Article 832502. https://doi.org/10.3389/fpls.2022.832502.
DOI: https://doi.org/10.3389/fpls.2022.832502

Interpretive Summary: Chitin turns on plant defenses against fungal disease. The fungus Fusarium graminearum causes Fusarium head blight (FHB), a disease of wheat and barley. FHB not only reduces crop yield but also contaminates grain with a fungal toxin called vomitoxin. One way that plants react to fungal infection is by releasing reactive oxygen species (ROS). ARS researchers in Peoria, Illinois, evaluated ROS responses in different parts of wheat and barley plants that had been treated with chitin, a polysaccharide that is a major component of fungal cell walls, insect exoskeletons, and crustacean shells. While there was no ROS burst in wheat leaves treated with chitin, typical ROS responses were found in barley leaves and in the stems of wheat heads, the route by which FHB spreads. This study identified defense genes were turned on in wheat heads treated with chitin but were suppressed in those infected with Fusarium. The genes identified may serve as novel targets to improve disease resistance. In addition, this study suggests that treating plants with chitin may boost their immunity and increase resistance to Fusarium Head Blight.

Technical Abstract: Fusarium graminearum is one of the primary causal agents of Fusarium head blight (FHB) on wheat and barley. FHB reduces grain yield and contaminates grain with various mycotoxins, including deoxynivalenol (DON). DON acts as a virulence factor to promote the fungus passing the rachis node and spreading throughout the head of wheat but not barley. Reactive oxygen species (ROS) are one of the earliest defense responses during plant and pathogen interactions. However, the complex roles of ROS during FHB development remain unclear. We investigated immune responses in wheat triggered by chitin, a major component of fungal cell walls. We revealed that no ROS burst was detected in chitin-treated wheat leaves, whereas a typical ROS peak was triggered by chitin in barley leaves. Interestingly, ROS were induced by chitin in wheat rachis nodes, which are critical barriers for FHB spread in wheat. We demonstrated a positive correlation between ROS levels in wheat rachis nodes and FHB spread. Further, defense genes were induced in wheat heads and rachis nodes treated with chitin, however, several chitin induced genes were suppressed in wheat heads infected with F. graminearum. The chitin-induced genes may serve as novel targets to enhance FHB resistance and food safety.