Trichoderma spp. are widely used in plant disease control and growth promotion due to their high efficacy and multiple biocontrol mechanisms. Trichoderma koningiopsis T-51 is an effective biocontrol agent against gray mold disease by direct contact. However, the indirect physical contact biocontrol potential of Trichoderma spp. is not clear. In this study, the volatile organic compounds (VOCs) produced by T-51 showed high inhibitory activity against plant pathogenic fungi Botrytis cinerea and Fusarium oxysporum. The percentage of B. cinerea and F. oxysporum mycelial growth inhibition by T-51 VOCs was 73.78% and 43.68%, respectively. In both B. cinerea and F. oxysporum, conidial germination was delayed, and germ tube elongation was suppressed when exposed to T-51 VOCs, and the final conidial germination rate of B. cinerea decreased significantly after T-51 treatment. The VOCs from T-51 reduced the Botrytis fruit rot of tomato compared with that noted when using the control. Moreover, the T-51 VOCs significantly increased the size and weight of Arabidopsis thaliana seedlings. Twenty-four possible compounds, which were identified as alkenes, alkanes, and esters, were detected in VOCs of T-51. These results indicate that T. koningiopsis T-51 can exert biological control by integrating actions to suppress plant disease and promote plant growth.

Trichoderma species are a group of fungi which is widely distributed in major terrestrial ecosystems; they are also commonly used as biocontrol agents for many plant diseases. A virus, namely Trichoderma harzianum hypovirus 1 (ThHV1), was identified in T. harzianum isolate T-70, and also infected isolate T-70D, together with its defective RNA (ThHV1-S). The ThHV1 genome possessed two Open Reading Frames (ORFs), namely ORF1 and ORF2. The start codon of ORF2 overlapped with the stop codon of ORF1 in a 43 nt long region. The polypeptide encoded by ORF2 of ThHV1 shared sequence similarities with those of betahypoviruses, indicating that ThHV1 is a novel member of Hypoviridea. Isolate T-70D, carrying both ThHV1 and ThHV1-S, showed abnormal biological properties, notably a decreased mycoparasitism ability when compared with isolate T-70. Both ThHV1 and ThHV1-S could be vertically transmitted to conidia and horizontally transmitted to T. harzianum isolate T-68 and T. koningiopsis T-51. The derivative strains carrying both ThHV1 and ThHV1-S showed decreased mycoparasitism ability, whereas strains carrying ThHV1 alone were normal, indicating that ThHV1-S is closely associated with the decreased mycoparasitism ability of T. harzianum isolate T-70D. ThHV1 was widely detected in isolates of T. harzianum, T. koningiopsis and T. atroviride originating from soil of China. Therefore, viruses in fungal biocontrol agents may also be a factor associated with the stability of their application.

Mycoviruses widely exist in filamentous fungi and sometimes cause phenotypic changes in hosts. Trichoderma harzianum hypovirus 1 (ThHV1) and its defective RNA ThHV1-S were found in T. harzianum and exhibited high transmissibility. In our previous study, ThHV1 and ThHV1-S were transferred to an excellent biological control agent T. koningiopsis T-51 to form a derivative strain 51-13. In this study, we assessed the metabolic changes in strain 51-13 and antifungal activity of its culture filtrate (CF) and volatile organic compounds (VOCs). The antifungal activity of CF and VOCs of T-51 and 51-13 was different. Compared with the CF of T-51, that of 51-13 exhibited high inhibitory activity against B. cinerea, Sclerotinia sclerotiorum, and Stagonosporopsis cucurbitacearum but low inhibitory activity against Leptosphaeria biglobosa and Villosiclava virens. The VOCs of 51-13 exhibited high inhibitory activity against F. oxysporum but low inhibitory activity against B. cinerea. The transcriptomes of T-51 and 51-13 were compared; 5531 differentially expressed genes (DEGs) were identified in 51-13 with 2904 up- and 2627 downregulated genes. In KEGG enrichment analysis, 1127 DEGs related to metabolic pathways (57.53%) and 396 DEGs related to biosynthesis of secondary metabolites (20.21%) were clearly enriched. From the CF of T-51 and 51-13, 134 differential secondary metabolites (DSMs) were detected between T-51 and 51-13 with 39 up- and 95 downregulated metabolites. From these, 13 upregulated metabolites were selected to test their antifungal activity against B. cinerea. Among them, indole-3-lactic acid and p-coumaric acid methyl ester (MeCA) exhibited strong antifungal activity. The IC₅₀ of MeCA was 657.35 μM and four genes possibly related to the synthesis of MeCA exhibited higher expression in 51-13 than in T-51. This study revealed the mechanism underlying the increase in antifungal activity of T-51 because of the mycovirus and provided novel insights in fungal engineering to obtain bioactive metabolites via mycoviruses.

Cucumber (Cucumis sativus) fruit spines are a classic material for researching the development of multicellular trichomes. Some key genes that influence trichome development have been confirmed to be associated with cuticle biosynthesis and secondary metabolism. However, the biological mechanisms underlying trichome development, cuticle biosynthesis, and secondary metabolism in cucumber remain poorly understood. CsTs, a C-type lectin receptor-like kinase gene, reportedly causes a tender trichome phenotype in cucumber when it mutates. In this study, the role of CsTs in cucumber fruit spines morphogenesis was confirmed using gene editing technology. Sectioning and cell wall component detection were used to analyse the main reason of tender fruit spines in the ts mutant. Subsequently, transcriptome data and a series of molecular biology experiments were used to further investigate the relationship between CsTs and cytoskeletal homeostasis in cucumber. CsTs overexpression partially compensated for the abnormal trichome phenotype of an Arabidopsis homolog mutant. Genetic hybridization and metabolic analysis indicated that CsTs and CsMict can affect trichome development and cuticle biosynthesis in the same pathway. Our findings provide important background information for further researching on the molecular mechanism underlying cucumber trichome development and contribute to understanding the biological function of C-type lectin receptor-like kinases.

Soil salinisation has become one of the major abiotic stresses limiting crop growth in the world. To enhance soybean productivity on saline lands, understanding its salt-stress response and underlying mechanisms is necessary. In this study, the salt-tolerant soybean Kefeng 1 and the salt-sensitive soybean Qihuang 1 were used to elucidate the synergistic regulatory networks underlying soybean salt tolerance. After 12 days of 150 mM NaCl treatment, both varieties were subjected to phenotypic evaluation, physiological measurements, and integrated transcriptomic and metabolomic analysis. The results showed that the salt tolerance in Kefeng 1 primarily originated from its root. Under salt stress, Kefeng 1 maintained Na⁺/K⁺ ion homeostasis by up-regulating Cation/H⁺ Exchanger 15 (CHX15) and Cation Exchanger 3 (CAX3), and down-regulating Cyclic Nucleotide-Gated Channel 13 (CNGC13). Furthermore, Kefeng 1 stabilised auxin (IAA) homeostasis by inhibiting IAA biosynthesis and regulating concentrations through PIN-FORMED 3 (PIN3)-mediated efflux. It also scavenged reactive oxygen species (ROS) by employing enhanced enzymatic antioxidant systems, specifically aldo-keto reductase 1 (AKR1), glutathione S-transferase (GST), and catalase (CAT), alongside non-enzymatic antioxidants like the isoflavone genistein. Gene–metabolite correlation network analysis identified Glyma.09G117900 (PIN3) and Glyma.19G244200 (AKR1) as two hub genes. These two genes were specifically up-regulated in Kefeng 1 root under NaCl stress, and the proteins they encoded played important roles in salt tolerance in Kefeng 1 root as described above. Accordingly, these two genes were identified as candidate genes for salt tolerance in Kefeng 1. This study offered a theoretical framework and genetic resources for developing salt-tolerant soybean cultivars.