Abstract
Gα signaling pathway as well as the global regulator LaeA were demonstrated to positively regulate the biosynthesis of chaetoglobosin A (ChA), a promising biotic pesticide produced by Chaetomium globosum. Recently, the regulatory function of Zn2Cys6 binuclear finger transcription factor CgcheR that lies within the ChA biosynthesis gene cluster has been confirmed. However, CgcheR was not merely a pathway specific regulator. In this study, we showed that the homologs gene of CgcheR (designated as Cgtf1) regulate ChA biosynthesis and sporulation in C. globosum NK102. More importantly, RNA-seq profiling demonstrated that 1,388 genes were significant differentially expressed as Cgtf1 deleted. Among them, a putative C2H2 transcription factor, named Cgtf6, showed the highest gene expression variation in zinc-binding proteins encoding genes as Cgtf1 deleted. qRT-PCR analysis confirmed that expression of Cgtf6 was significantly reduced in CgTF1 null mutants. Whereas, deletion of Cgtf6 resulted in the transcriptional activation and consequent increase in the expression of ChA biosynthesis gene cluster and ChA production in C. globosum. These data suggested that CgTF6 probably acted as an end product feedback effector, and interacted with CgTF1 to maintain a tolerable concentration of ChA for cell survival.
Highlights
Chaetomium globosum is ubiquitous in the environment
Blastp analysis revealed that CgTF1 had 77.19, 38.10, 30.56, 26.10 and 24.64% identity to a GAL4-like Zn2Cys6 binuclear cluster DNA-binding domain protein (C. globosum E-C-2, QHD43140.1), CheC (P. expansum, CAO91859.1), CheF (P. expansum, CAO91864.1), GAL4 (Aspergillus sclerotialis, RJE27110.1) and Gal4p (S. cerevisiae, NP_015076.1), respectively
A growing number of data suggests that the main secondary metabolites of this species, chaetoglobosin A, can be developed in the biocontrol of nematode, sap-sucking pests and phytopathogenic fungi
Summary
Chaetomium globosum is ubiquitous in the environment CgTF6 Inhibits ChA Biosynthesis degrading fungus, exhibited strong nematicidal activity against M. incognita, and the main active component was identified as chaetoglobosin A [ChA, the median lethal concentration (LC50) is 77.0 μg/ml] (Hu et al, 2013, 2018). ChA, other secondary metabolites of C. globosum, e.g., chaetoglobosin B and flavipin are exhibited strong nematicidal activities against the second stage juveniles of M. javanica, with LC50 values of 107.7 and 99.2 μg/ml after 72 h, respectively (Khan et al, 2019). Taken together, published data clearly demonstrate that it is possible to explore the nematicidal activity of C. globosum, and ChA can be used as a biological agent for the control of plant pathogenic microorganisms and pests
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