The veA gene is necessary for the negative regulation of the veA expression in Aspergillus nidulans

Global regulatory factor VeA upregulates the production of antitumor substances in endophytic Fusarium solani

A number of studies have demonstrated that endophytic fungi have the potential to produce antitumor active substances with novel structures and significant activities. In our previous studies, we isolated a Fusarium strain from the stem of the medicinal plant Nothapodytes pittosporoides (Oliv.). In this study, we identified this strain as Fusarium solani and found that its crude extract has significant antitumor activity against human alveolar adenocarcinoma cells (A549). We overexpressed the global regulatory factor VeA in F. solani (VeA^OE), resulting in a significant increase in antitumor activity. The MTT assay results showed that the inhibition rate of the VeA^OE mutant extract on A549 cancer cells was significantly higher than that of the WT extract, as the IC₅₀ decreased from 369.22 to 285.89 μg/mL, and the apoptosis ratio was significantly increased by approximately 4.86-fold. In VeA^OE, accumulation of alkaloids, terpenoids, carboxylic acid derivatives, phenols and flavonoid metabolites with potential antitumor activity was significantly increased compared with WT based on metabolomic analysis. Additionally, transcriptome analysis found that the expression patterns of 48 genes related to antitumor activity were significantly changed in VeA^OE, mainly involving glycosyl hydrolases, the Zn(2)-Cys(6) class, cytochrome P450 monooxygenase, 3-isopropylmalate dehydratase, and polyketide synthases. These results suggested that VeA mediated the antitumor activity of the metabolites in F. solani HB1-J1 by regulating multiple metabolic pathways.

Comparative proteomic analysis reveals the regulatory network of the veA gene during asexual and sexual spore development of Aspergillus cristatus

Aspergillus cristatus is the predominant fungal population during fermentation of Chinese Fuzhuan brick tea, and belongs to the homothallic fungal group that undergoes a sexual stage without asexual conidiation under hypotonic conditions, while hypertonic medium induces initiation of the asexual stage and completely blocks sexual development. However, the veA deletion mutant only produces conidia in hypotonic medium after a 24-h culture, but both asexual and sexual spores are observed after 72 h. The veA gene is one of the key genes that positively regulates sexual and negatively regulates asexual development in A. cristatus. To elucidate the molecular mechanism of how VeA regulates asexual and sexual spore development in A. cristatus, 2D electrophoresis (2-DE) combined with MALDI-tandem ToF MS analysis were applied to identify 173 differentially expressed proteins (DEPs) by comparing the agamotype (24 h) and teleomorph (72 h) with wild-type (WT) A. cristatus strains. Further analysis revealed that the changed expression pattern of Pmk1-MAPK and Ser/Thr phosphatase signaling, heat shock protein (Hsp) 90 (HSP90), protein degradation associated, sulphur-containing amino acid biosynthesis associated, valine, leucine, isoleucine, and arginine biosynthesis involved, CYP450 and cytoskeletal formation associated proteins were involved in the production of conidia in agamotype of A. cristatus. Furthermore, the deletion of veA in A. cristatus resulted in disturbed process of transcription, translation, protein folding, amino acid metabolism, and secondary metabolism. The carbohydrate and energy metabolism were also greatly changed, which lied in the suppression of anabolism through pentose phosphate pathway (PPP) but promotion of catabolism through glycolysis and tricarboxylic acid (TCA) cycle. The energy compounds produced in the agamotype were mainly ATP and NADH, whereas they were NADPH and FAD in the teleomorph. These results will contribute to the existing knowledge on the complex role of VeA in the regulation of spore development in Aspergillus and provide a framework for functional investigations on the identified proteins.

Trichoderma: sensing the environment for survival and dispersal

Species belonging to the genus Trichoderma are free-living fungi common in soil and root ecosystems, and have a broad range of uses in industry and agricultural biotechnology. Some species of the genus are widely used biocontrol agents, and their success is in part due to mycoparasitism, a lifestyle in which one fungus is parasitic on another. In addition Trichoderma species have been found to elicit plant defence responses and to stimulate plant growth. In order to survive and spread, Trichoderma switches from vegetative to reproductive development, and has evolved with several sophisticated molecular mechanisms to this end. Asexual development (conidiation) is induced by light and mechanical injury, although the effects of these inducers are influenced by environmental conditions, such as nutrient status and pH. A current appreciation of the links between the molecular participants is presented in this review. The photoreceptor complex BLR-1/BLR-2, ENVOY, VELVET, and NADPH oxidases have been suggested as key participants in this process. In concert with these elements, conserved signalling pathways, such as those involving heterotrimeric G proteins, mitogen-activated protein kinases (MAPKs) and cAMP-dependent protein kinase A (cAMP-PKA) are involved in this molecular orchestration. Finally, recent comparative and functional genomics analyses allow a comparison of the machinery involved in conidiophore development in model systems with that present in Trichoderma and a model to be proposed for the key factors involved in the development of these structures.

A hypothesis to explain how LaeA specifically regulates certain secondary metabolite biosynthesis gene clusters

Biosynthesis of mycotoxins involves transcriptional co-regulation of sets of clustered genes. We hypothesise that specific control of transcription of genes in these clusters by LaeA, a global regulator of secondary metabolite production and development in many filamentous fungi, results from its interaction with a Cys6Zn2 DNA-binding protein unique to the gene cluster.

Regulation of morphogenesis and biocontrol properties in Trichoderma virens by a VELVET protein, Vel1

Mycoparasitic strains of Trichoderma are applied as commercial biofungicides for control of soilborne plant pathogens. Although the majority of commercial biofungicides are Trichoderma based, chemical pesticides, which are ecological and environmental hazards, still dominate the market. This is because biofungicides are not as effective or consistent as chemical fungicides. Efforts to improve these products have been limited by a lack of understanding of the genetic regulation of biocontrol activities. In this study, using gene knockout and complementation, we identified the VELVET protein Vel1 as a key regulator of biocontrol, as well as morphogenetic traits, in Trichoderma virens, a commercial biocontrol agent. Mutants with mutations in vel1 were defective in secondary metabolism (antibiosis), mycoparasitism, and biocontrol efficacy. In nutrient-rich media they also lacked two types of spores important for survival and development of formulation products: conidia (on agar) and chlamydospores (in liquid shake cultures). These findings provide an opportunity for genetic enhancement of biocontrol and industrial strains of Trichoderma, since Vel1 is very highly conserved across three Trichoderma species.