Stress-Activated Protein Kinase Signalling Regulates Mycoparasitic Hyphal-Hyphal Interactions in Trichoderma...

Area of Science:

• Mycology
• Plant Pathology
• Molecular Biology

Background:

• Trichoderma atroviride is a mycoparasitic fungus vital for biological control of plant pathogens.
• Successful mycoparasitism relies on recognizing and responding to prey-derived signals.
• GTPase and MAPK signaling pathways are implicated in fungal development and interaction.

Purpose of the Study:

• To investigate the role of GTPase activity and MAPK signaling in Trichoderma atroviride's morphogenetic response to fungal prey.
• To elucidate the specific functions of Trichoderma MAPK 1 (Tmk1) and Tmk3 in the process of mycoparasitism.

Main Methods:

• Utilized microcolony confrontation assays with reporter strains to visualize GTPase activity (Cdc42 and Rac1 CRIB reporters).
• Performed microscopic analysis to observe morphogenetic changes and polarity stress during interaction.
• Generated and analyzed Tmk1 and Tmk3 deletion mutants to assess their impact on mycoparasitism.

Main Results:

• Trichoderma atroviride exhibited significant polarity stress upon approaching fungal prey.
• Deletion of Tmk1 or Tmk3 severely impaired tip polarization, chemotropic growth, and contact-induced morphogenesis, hindering mycoparasitism.
• Tmk3 influenced pre-contact polarity adaptation, while Tmk1 regulated early contact-induced morphogenesis, with prey species-specific variations observed.

Conclusions:

• The GTPase/MAPK signaling network, particularly Tmk1 and Tmk3, is essential for Trichoderma atroviride's successful mycoparasitism.
• These kinases play distinct roles in different stages of the interaction, highlighting the complexity of signal integration.
• A robust polarized tip growth apparatus is critical for effective biological control mediated by Trichoderma species.