Bacteria vs fungi: not even a struggle
Researchers from the Dong-A University and the Pusan National University (Busan, Korea), the University of Oklahoma (USA) and the Kyungpook National University (Daeguand, Korea) explored the bacterial-fungus interaction between Burkholderia glumae and Fusarium graminearum.
- Cooperative interaction between the seed-borne Burkholderia glumae and the plant pathogenic fungus Fusarium graminearum
- Bacterial survival, bacterial and fungal dispersal and disease progression on rice plants are promoted by this interaction
- Burkholderia glumae physically attaches to Fusarium graminearum to achieve a rapid and expansive dispersal and enhance disease severity
A research team from the Dong-A University and the Pusan National University (Busan, Korea), the University of Oklahoma (USA) and the Kyungpook National University (Daeguand, Korea), leaded by Young-Su Seo and Jungkwan Lee, published an interesting paper on the relationship between the seed-borne bacterium Burkholderia glumae - the causal agent of panicle blight in rice field - and the plant pathogenic fungus Fusarium graminearum. B. glumae produces toxoflavin, an antimicrobial, virulence factor that induces production of ROS (Reactive Oxygen Species) and F. graminearum is able to resist to toxoflavin.
The paper focused on the mechanism by which F. graminearum develops resistance to toxoflavin, by using fungal toxoflavin-sensitive mutant strains and performing experiments in planta. Transcriptomic analysis of F. gramiearun strains in response to toxoflavin showed that the greatest sensitivity to toxoflavin occurred in relation to an up-regulation of genes involved in the fatty acid biosynthesis pathway with the involvement also of the superoxide dismutase I. Interaction between B. glumae and F. graminearum leads to positive effects on both the organisms: F. graminearum enhances spore production and deoxynivalenol biosynthesis with an increase in disease severity on rice, while B. glumeae is protected by UV stress.
Bacterial-fungus interactions are widely spread in nature and can lead to different biological effects varying from antagonism to cooperation. Metabolite exchanges, signaling chemotaxis and physical communication are often involved in these interactions. Data here collected provides the opportunity to target this association and reduce its virulence and are of example for other cooperative systems.
Bacterial-fungal interactions are widely found in distinct environments and contribute to ecosystem processes. Previous studies of these interactions have mostly been performed in soil, and only limited studies of aerial plant tissues have been conducted. Here we show that a seed-borne plant pathogenic bacterium, Burkholderia glumae (Bg), and an air-borne plant pathogenic fungus, Fusarium graminearum (Fg), interact to promote bacterial survival, bacterial and fungal dispersal, and disease progression on rice plants, despite the production of antifungal toxoflavin by Bg. We perform assays of toxoflavin sensitivity, RNA-seq analyses, lipid staining and measures of triacylglyceride content to show that triacylglycerides containing linolenic acid mediate resistance to reactive oxygen species that are generated in response to toxoflavin in Fg. As a result, Bg is able to physically attach to Fg to achieve rapid and expansive dispersal to enhance disease severity.
NATURE COMMUNICATIONS 9,31(2018) doi:10.1038/s41467-017-02430-2 Cooperative interactions between seed-borne bacterial and air-borne fungal pathogens on rice. Boknam Jung, Jungwook Park, Namgyu Kim, Taiying Li, Soyeon Kim, Laura E. Bartley, Jinnyun Kim, Inyoung Kim, Yoonhee Kang, Kihoon Yun, Younghae Choi, Hyun-Hee Lee, Sungyeon Ji, Kwang Sik Lee, Bo Yeon Kim, Jong Cheol Shon, Won Cheol Kim, Kwang-Hyeon Liu, Dahye Yoon, Suhkman Kim, Young-Su Seo, Jungkwan Lee