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Summary: Hypocrealean Trichoderma are the most extensively studied facultative mycoparasites against phytopathogenic fungi. Aerial hyphae of Trichoderma guizhouense can rapidly proliferate over Fusarium oxysporum hyphae, cause sporadic cell death and arrest the growth of the host. The results of the present study demonstrated that a unique short‐chain dehydrogenase/reductase (SDR), designated as TgSDR1, was expressed at a high level in T. guizhouense challenged by the hosts. Similar to other SDRs family members, the TgSDR1 protein contains a cofactor‐binding motif and a catalytic site. The subcellular localization assay revealed that the TgSDR1::GFP fusion protein translocated to lipid droplets in mycelia and conidia. The data obtained using reverse genetic approach indicated that TgSDR1 is associated with antifungal ability, plays an important role in providing reducing equivalents in the form of NADPH and regulates the amino sugar and nucleotide sugar metabolism in T. guizhouense upon encountering a host. Moreover, the TgSDR1 deletion mutant was defective in conidiation. Thus, TgSDR1 functions as a key metabolic enzyme in T. guizhouense to regulate mycotrophic interactions, defence against other fungi, such as F. oxysporum, and conidiation. [ABSTRACT FROM AUTHOR]

Summary: Filamentous fungi are known as producers of a large array of diverse secondary metabolites (SMs) that aid in securing their environmental niche. Here, we demonstrated that the SMs have an additional role in fungal defence against other fungi: Trichoderma guizhouense, a mycoparasite, is able to antagonize Fusarium oxysporum f. sp. cubense race 4 (Foc4) by forming aerial hyphae that kill the host with hydrogen peroxide. At the same time, a gene cluster comprising two polyketide synthases is strongly expressed. Using functional genetics, we characterized this cluster and identified its products as azaphilones (termed as trigazaphilones). The trigazaphilones were found lacking of antifungal toxicity but exhibited high radical scavenging activities. The antioxidant property of trigazaphilones was in vivo functional under various tested conditions of oxidative stress. Thus, we conclude that the biosynthesis of trigazaphilones serves as a complementary antioxidant mechanism and defends T. guizhouense against the hydrogen peroxide that it produces to combat other fungi like Foc4. [ABSTRACT FROM AUTHOR]

Summary: When resources are limited, the hypocrealean fungus Trichoderma guizhouense can overgrow another hypocrealean fungus Fusarium oxysporum, cause sporadic cell death and arrest growth. A transcriptomic analysis of this interaction shows that T. guizhouense undergoes a succession of metabolic stresses while F. oxysporum responded relatively neutrally but used the constitutive expression of several toxin‐encoding genes as a protective strategy. Because of these toxins, T. guizhouense cannot approach it is potential host on the substrate surface and attacks F. oxysporum from above. The success of T. guizhouense is secured by the excessive production of hydrogen peroxide (H2O2), which is stored in microscopic bag‐like guttation droplets hanging on the contacting hyphae. The deletion of NADPH oxidase nox1 and its regulator, nor1 in T. guizhouense led to a substantial decrease in H2O2 formation with concomitant loss of antagonistic activity. We envision the role of NOX proteins in the antagonism of T. guizhouense as an example of metabolic exaptation evolved in this fungus because the primary function of these ancient proteins was probably not linked to interfungal relationships. In support of this, F. oxysporum showed almost no transcriptional response to T. guizhouense Δnox1 strain indicating the role of NOX/H2O2 in signalling and fungal communication. [ABSTRACT FROM AUTHOR]

T richoderma guizhouense NJAU 4742 ( Harzianum clade) can suppress the causative agent of banana wild disease F usarium oxysporum f. sp. cubense 4 (Foc4). To identify genes involved in this trait, we used T- DNA insertional mutagenesis and isolated one mutant that was unable to overgrow Foc4 and had reduced antifungal ability. Using the high-efficiency thermal asymmetric interlaced- PCR, the T- DNA was located in the terminator of a neutral metalloprotease gene (encoding a MEROPS family M35 protease), which was named nmp1. The antifungal activity of the mutant was recovered by retransformation with wild-type nmp1 gene. The purified NMP1 (overexpressed in P ichia pastoris) did not inhibit the growth and germination of other fungi in vitro. Its addition, however, partly recovered the antifungal activity of the mutant strain against some fungi. The expression of nmp1 is induced by the presence of fungi and by dead fungal biomass, but the time-course of transcript accumulation following the physical contact depends on mode of interaction: it increases in cases of long-lasting parasitism and decreases if the prey fungus is dead shortly after or even before the contact (predation). We thus conclude that NMP1 protein of T . guizhouense has major importance for mycotrophic interactions and defence against other fungi. [ABSTRACT FROM AUTHOR]