Deciphering the fungal immune response: global gene regulation governed by the Fusarium graminearum mRNA-binding protein CSX1 in response to virus infection.

• Applicant: Professor Dr. Jörg Bormann
• Subject Area: Plant Breeding and Plant Pathology ; Biochemistry ; Parasitology and Biology of Tropical Infectious Disease Pathogens
• Term: from 2015 to 2017
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 283589647

The work of the applicant deals with the infection biology of Fusarium graminearum, one of the most devastating plant pathogens on small grain cereals worldwide. Economic losses by Fusarium infections are running into billions Euro each year. The proposed project deals with the interaction of the mycovirus FgV-Ch9 with F. graminearum. Infection of mycelia with virus renders the fungus impaired in vegetative growth, sexual and asexual propagation, and virulence. These phenotypes share a high degree of identity with those observed after genetic inactivation of the mRNA-stabilizing protein CSX1 in F. graminearum. A functional connection between virus infection and CSX1 was further substantiated by transcription analysis: a virus infection leads to a drastic down-regulation of CSX1 whereas a constitutive expression of CSX1 prevents the development of symptoms after virus infection. It can be concluded that the expression level of CSX1 determines the fitness of the fungus. The virus-triggered down-regulation of CSX1 might, therefore, represent a novel and, as yet undescribed, immune reaction of the fungus. To verify this assumption, the applicant plans to analyze the global transcriptional rearrangements in the virus-infected fungus and the CSX1 mutants (deletion and over-expression mutants) by transcriptome sequencing. Goal is to identify genes equally affected by virus infection and CSX1 deletion. Those genes presumably build up the immune system and shall subsequently be functionally characterized as well. In order to further analyze the importance of CSX1 in terms of gene regulation by mRNA-stabilization, global mRNA-decay rates shall be assayed by use of mRNA-sequencing. Finally, specific mRNAs that are bound by CSX1 shall be identified. For this, these transcripts will be covalently linked to CSX1 and subsequently sequenced. In summary these experiments may prove the existence of a fungal immune system. Essential and auxiliary components of this novel system will be identified by binding assays and transcriptome sequencing. New insights in the regulation of fungal immune reactions will pave the way to innovative resistance breeding strategies.

• DFG Programme: Research Fellowships
• International Connection: USA
• Host: Professor Dr. Michael Freitag