In nature, plants are constantly exposed to a wide range of microorganisms, including pathogenic and beneficial microbes. On a global scale, plant pathogenic microbes represent a major threat to global food and feed production, highlighting the importance of research on this topic.

Regardless of being extracellular or intracellular, all bacterial, fungal and oomycete phytopathogens first encounter the host apoplast. The host apoplast contains a wide range of defense related components, such as glycoside hydrolases, proteases, peroxidases, antimicrobial proteins and secondary metabolites, which are detrimental for colonization of pathogens. In addition to plant apoplastic defense components, the apoplast also contains endophytic microbial communities that promote growth of their host by increasing its tolerance/resistance to abiotic and biotic stresses. Any microbe, which are not able to successfully overcome either apoplastic immunity or microbial community, will be restricted at the site of penetration.

To establish disease, adapted plant pathogens secrete effector proteins to suppress host defense responses and reprogram host physiology. Although relatively many studies have been performed to understand the function of effectors on manipulation of host plant immunity, there is still very limited information on if/how effectors are involved in modulation of host microbial communities. This project aims to dissect effector-mediated disease establishment of biotrophic fungal pathogens by using the well-established Ustilago hordei-barley pathosystem as a model. In this regard, we will use and combine proteomics, biochemical, molecular and cell biological expertise to investigate the following central questions: i) How does U. hordei modulate apoplastic immunity of the host plant? ii) If/How do effectors from U. hordei contribute to host colonization via modulation host leaf microbiota?

Successful disease control strategies require better understanding of functional biology of effectors on both manipulation of host defense and host microbiota. The results gained from this proposal will provide potential novel targets for developing effective and sustainable disease control strategies.

Main investigator: Dr. Bilal Ökmen https://sites.google.com/view/okmen-lab/home