Mechanisms leading to antagonism

Ecological systems word-wide including cropland are affected by climate changes and therefore the spread of plant pathogenic fungi as well as the contamination of water resources due to the increasing application of chemical fungicides threaten human and animal livelihood. In this context, biological pest control represents a serious alternative to conventional fungicides. Biocontrol active Trichoderma spp. were shown to meet these demands as they recognize and lyse various pathogenic fungi due to complex and yet not fully understood mechanisms involving morphological changes and the production of hydrolytic enzymes and antibiotic metabolites. Additionally, these species promote plant growth and induce systemic resistance in different plants. In the present proposal it is planned to elucidate the role of differentially expressed genes found during mycoparasitism of T. atroviride IMI206040 against fungi from distinct phyla concerning their function in host specificity, host recognition, mycoparasitism and biocontrol. To this end, 17 genes without predicted function of the corresponding protein and 9 genes with related function to mechanisms involved in antagonism were chosen for characterization throughout the proposed project. Amongst these are genes encoding for proteins participating in signal transduction, defense, autophagy, secondary metabolites biosynthesis, and intracellular trafficking, secretion, and vesicular transport. The strategy pursued to characterize and annotate all 26 gene products is the generation of deletion mutants and/or mutants over-expressing the corresponding gene and to determine their function in recognition of and mycoparasitic behavior against various plant pathogenic fungi (e.g. Rhizoctonia solani, Phytophthora capsici, and Botrytis cinerea). Furthermore, mutant strains strongly affected in their antagonistic ability will be compared to the parental strain concerning the production of secondary metabolites, secreted proteins, and their biocontrol abilities.

Trichoderma spp. are scientific and economic important soil borne fungi with applications in distinct areas, e.g. food and feed production, biological pest control and plant growth promotion. Anyway, especially in the field of plant protection against fungal diseases of agricultural crops too little is known concerning recognition and specificity of Trichoderma against these fungi in general. But also regarding the genes involved in these mechanisms in detail. On behalf of that, the present project was realized to identify and characterize genes involved in the specific response of T. atroviride against various distinct plant-pathogenic fungi. Of a list of 175 differentially expressed genes during different stages of interaction of Trichoderma against its host fungi, seven were chosen for further characterization. Although different transcript levels of some genes were detected, their influence on the behavior of T. atroviride against the chosen pathogens could not be proven. On the other hand, the involvement of the fungal transcription factor Xyr1, well characterized in T. reesei, could be described in more detail for T. atroviride during plant protection.