Trichoderma spp. are biological control agents extensively used against various plant pathogens. However, the key genes shared for the growth, development and biological activity are unclear. In this study, we explored the genes responsible for the growth and development of T. asperellum GDFS 1009 under liquid-shaking culture compared to solid-surface culture. Transcriptome analysis revealed 2744 differentially expressed genes, and RT-qPCR validation showed that the high-affinity methionine permease MUP1 was the key gene for growth under different media. Deletion of the MUP1 inhibited the transport of amino acids, especially methionine, thereby inhibiting mycelial growth and sporulation, whereas inhibition could be mitigated by adding methionine metabolites such as SAM, spermidine and spermine. The MUP1 gene responsible for the methionine-dependent growth of T. asperellum was confirmed to be promoted through the PKA pathway but not the MAPK pathway. Furthermore, the MUP1 gene also increased the mycoparasitic activity of T. asperellum against Fusarium graminearum. Greenhouse experiments revealed that MUP1 strengthens the Trichoderma-induced crop growth promotion effect and SA-induced pathogen defense potential in maize. Our study highlights the effect of the MUP1 gene on growth and morphological differentiation and its importance for the agricultural application of Trichoderma against plant diseases.

The pathogenic plant fungus Bipolaris maydis is responsible for southern corn leaf blight (SCLB), a widespread agricultural disease that significantly reduces maize yield in various agroecological zones. The present research focuses on characterizing the role of Trichoderma harzianum cellobiohydrolase (CBH) Thph2 in induced maize resistance to SCLB by triggering the production of reactive oxygen species (ROS) in leaves. First of all, we demonstrated the potential activities of Thph2 in triggering ROS burst and PDC in a model plant, Nicotiana benthamiana. Cell death, ROS burst, and programmed cell death (PCD) were observed in N. benthamiana leaves following transient expression of Thph2, indicating its defensive role against Sclerotinia sclerotiorum infection. The removal of the signal peptide from Thph2 resulted in the complete loss of the cell death phenotype and the accumulation of reactive oxygen species (ROS), confirming that Thph2 functions as a microbial elicitor that primes host plant immunity through ROS-mediated signaling, thereby inducing systemic resistance (ISR). Furthermore, the Thph2 protein conferred resistance against B. maydis in maize, significantly increasing reactive oxygen species (ROS) accumulation (1.5-fold compared to the control) at 48 h post-inoculation (hpi),and leading to the reduction in the lesion area of SCLB by 15.9% at 2 days post-inoculation (dpi). Our results demonstrated that the Thph2 protein markedly enhanced the expression of lox5, aos, and hpl in maize leaves, thereby confirming its function in triggering plant defense mechanisms primarily via the jasmonic acid signaling pathway. This research reveals new molecular mechanisms by which T. harzianum enhances plant defense and showcases the biocontrol efficacy of Thph2 against southern corn leaf blight (SCLB).

Fusarium root rot (caused by Fusarium verticillioides) is a destructive soilborne disease in maize, significantly reducing crop yields. The root symbiotic fungi Trichoderma species have been confirmed as effective biocontrol microbes for Fusarium root rot; however, the mechanistic role of Trichoderma-induced endophytes in suppressing Fusarium root rot in maize remains unclear. This study found that Trichoderma harzianum T30 significantly reduced the abundance of pathogens by 48.9% and increased the abundance of potentially antagonistic Bacillus strains (33%) in the root endophytic bacterial community. In addition, the hyd1 gene in T. harzianum T30 induced a 7.5-fold upregulation of ZmOPR7 in maize roots compared to the Δhyd1 mutant treatment, a gene related to the jasmonic acid (JA) pathway. Further, several endophytic Bacillus strains were specifically induced by a hyd1-overexpressing strain, including B. amyloliquefaciens MX66, B. velezensis C9, and B. velezensis GAGAN3. Three endophytes significantly (p < 0.05) reduced Fusarium root rot incidence in maize by 46.6–55.0% and upregulated the expression of jasmonic acid/ethylene (JA/ET) pathway-related genes (ZmOPR7, ZmOPR8 and ZmEIL1) by 5.4-, 1.5-, and 4.6-fold, respectively, compared to untreated controls. Meanwhile, the Bacillus strain also improved maize plant growth. This study examined how overexpression of the T. harzianum elicitor gene hyd1 (in the OE-hyd1 strain) affects the colonization dynamics of beneficial endophytic bacteria in maize roots. Additionally, it further suggested the contribution of selected endophytic Bacillus strains in suppressing Fusarium root rot in maize.