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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 (H2 O2 ), 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 H2 O2 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/H2 O2 in signalling and fungal communication.

In this study, the growth of fungi Trichoderma guizhouense NJAU4742 was significantly inhibited under acid stress, and the genes related to acid stress were identified based on transcriptome analysis. Four genes including tna1, adh2/4, and bna3 were significantly up‐regulated. Meanwhile, intracellular hydrogen ions accumulated under acid stress, and ATP synthesis was induced to transport hydrogen ions to maintain hydrogen ion balance. The enhancement of glycolysis pathway was also detected, and a large amount of pyruvic acid from glycolysis was accumulated due to the activity limitation of PDH enzymes. Finally, acetaldehyde accumulated, resulting in the induction of adh2/4. In order to cope with stress caused by acetaldehyde, cells enhanced the synthesis of NAD+ by increasing the expression of tna1 and bna3 genes. NAD+ effectively improved the antioxidant capacity of cells, but the NAD+ supplement pathway mediated by bna3 could also cause the accumulation of kynurenine (KYN), which was an inducer of apoptosis. In addition, KYN had a specific promoting effect on acetaldehyde synthesis by improving the expression of eno2 gene, which led to the extremely high intracellular acetaldehyde in the cell under acidic stress. Our findings provided a route to better understand the response of filamentous fungi under acid stress. [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]

Different fertilization managements of red soil, a kind of Ferralic Cambisol, strongly affected the soil properties and associated microbial communities. The association of the soil microbial community and functionality with long-term fertilization management in the unique low-productivity red soil ecosystem is important for both soil microbial ecology and agricultural production. Here, 454 pyrosequencing analysis of 16S recombinant ribonucleic acid genes and GeoChip4-NimbleGen-based functional gene analysis were used to study the soil bacterial community composition and functional genes involved in soil organic carbon degradation. Long-term nitrogen-containing chemical fertilization-induced soil acidification and fertility decline and significantly altered the soil bacterial community, whereas long-term organic fertilization and fallow management improved the soil quality and maintained the bacterial diversity. Short-term quicklime remediation of the acidified soils did not change the bacterial communities. Organic fertilization and fallow management supported eutrophic ecosystems, in which copiotrophic taxa increased in relative abundance and have a higher intensity of labile- C-degrading genes. However, long-term nitrogen-containing chemical fertilization treatments supported oligotrophic ecosystems, in which oligotrophic taxa increased in relative abundance and have a higher intensity of recalcitrant- C-degrading genes but a lower intensity of labile- C-degrading genes. Quicklime application increased the relative abundance of copiotrophic taxa and crop production, although these effects were utterly inadequate. This study provides insights into the interaction of soil bacterial communities, soil functionality and long-term fertilization management in the red soil ecosystem; these insights are important for improving the fertility of unique low-productivity red soil. [ABSTRACT FROM AUTHOR]

In this study, the growth of fungi Trichoderma guizhouense NJAU4742 was significantly inhibited under acid stress, and the genes related to acid stress were identified based on transcriptome analysis. Four genes including tna1, adh2/4, and bna3 were significantly up-regulated. Meanwhile, intracellular hydrogen ions accumulated under acid stress, and ATP synthesis was induced to transport hydrogen ions to maintain hydrogen ion balance. The enhancement of glycolysis pathway was also detected, and a large amount of pyruvic acid from glycolysis was accumulated due to the activity limitation of PDH enzymes. Finally, acetaldehyde accumulated, resulting in the induction of adh2/4. In order to cope with stress caused by acetaldehyde, cells enhanced the synthesis of NAD + by increasing the expression of tna1 and bna3 genes. NAD + effectively improved the antioxidant capacity of cells, but the NAD + supplement pathway mediated by bna3 could also cause the accumulation of kynurenine (KYN), which was an inducer of apoptosis. In addition, KYN had a specific promoting effect on acetaldehyde synthesis by improving the expression of eno2 gene, which led to the extremely high intracellular acetaldehyde in the cell under acidic stress. Our findings provided a route to better understand the response of filamentous fungi under acid stress., (© 2022 Applied Microbiology International and John Wiley & Sons Ltd.)