P-252 - On the role of barley diterpenoid phytoalexins in the interaction with Bipolaris sorokiniana.

B. sorokiniana is a hemibiotrophic fungus responsible for several diseases in cereal crops, such as wheat and barley. In wheat alone, root system infections can lead to yield losses of up to 25%. Moreover, these infections have a high incidence in dry and warm areas; therefore, understanding the interaction between the plant and B. sorokiniana becomes crucial in the context of global warming. Phytoalexin diterpenoids are known defensive compounds produced by plants during infections. In barley, these newly discovered compounds, named hordedanes, have been shown to positively affect B. sorokiniana growth, while limiting other fungi such as Fusarium graminearum. To better understand the plant's response in the early stages of infection, transcriptomic and metabolomic experiments were conducted on barley seedlings. To assess the contribution of hordedanes to the interaction with B. sorokiniana, mutants of this pathway were also included. Differential expression and clustering analysis revealed several differentially expressed genes potentially involved in the biosynthesis, transcription regulation, and transport of hordedanes, as well as in the production of additional phytoalexins of different chemical classes, such as tryptophan derivatives and smiglasides. The presence of these additional phytoalexins was confirmed through metabolic profiling, thus providing a comprehensive picture of the chemical defense of barley roots in response to fungal infections.