Enlightening Gliotoxin Biological System in Agriculturally Relevant Trichoderma spp.

Abstract

Gliotoxin (GT) is a dual fungal secondary metabolite (SM). It displays pleiotropic activities and possesses medicinal properties and biocontrol abilities but, unfortunately, has toxic properties in humans. Various Trichoderma species are used as fungal biological control agents (BCAs), as a sustainable alternative for crop protection worldwide. Among them is Trichoderma virens, a GT-producing fungus. Since no information was available on the genetically coded prerequisites for the production of GT in other Trichoderma spp., genome analyses were carried out in 10 Trichoderma spp. genomes. Moreover, a realtime PCR assay setup ad hoc and high-performance liquid chromatography (HPLC) analyses were employed to understand the GT-producing biological systems in T. virens GV29-8 (TvGv29-8) and Trichoderma afroharzianum T6776 (TaT6776), two relevant biocontrol fungi. The structure of the GT biosynthesis genes (GT-BG) is polymorphic, with two distinct types associated with the ability to produce GT. GliH, a key protein for GT synthesis, is absent in most of the Trichoderma GT biosynthetic pathways, which may be the reason for their inability to produce GT. The GT-BG are expressed in TvGv29-8 as expected, while they are silent in TaT6776. Interestingly, in the GT-non-producing TaT6776, only gliA (putative GT transporter) and gtmA (putative GT S-methyltransferase) were induced by exogenous GT, underlining the ability of this strain to reduce the deleterious effect of the toxin. This ability is confirmed by growth assays and by the detection of the bis-thiomethylated form of GT catalyzed by GtmA in the culture medium supplemented with GT. To the best of our knowledge, this is the first general description of the GT biological system in different Trichoderma spp. as far as the GT-BG content and organization is concerned and a preliminary insight into their functionality.

Complete Genome Sequences and Genome-Wide Characterization of Trichoderma Biocontrol Agents Provide New Insights into their Evolution and Variation in Genome Organization, Sexual Development, and Fungal-Plant Interactions

“…In contrast, the GTX-BGCs in FT-333 and Gv29-8 have 10 such blocks. This unique property of GTX-BGCs had not been reported before because NGS sequence reads are too short to assemble chromosomal regions of low sequence complexity ( 36 ). We suggest that GTX-BGCs represent versatile systems for future experimental evolution studies to reveal the functional impacts of AT-rich blocks for the expression and regulation of GTX biosynthesis.…”

“…Fourth, T. virens has two species-specific BGCs: viridin (VIR)-BGC and gliotoxin (GTX)-BGC. These two SM-BGCs produce a group of furano-steroidal antibiotics and GTX or GTX-like compounds to compete with and restrict the growth of plant pathogenic fungi, respectively ( 36 , 62 ). CBS1-2, P1, and FT-101 possess none or only two orthologs of the VIR biosynthetic genes, respectively (Table S6).…”

It Works! Organic-Waste-Assisted Trichoderma spp. Solid-State Fermentation on Agricultural Digestate

“…qPCR was performed using the Real-Time PCR PowerUp SYBR Green Master Mix (Applied Biosystems, Waltham, MA, USA) in the 7500 Fast Real-Time PCR System (Thermo Fischer Scientific, Waltham, MA, USA). The oligonucleotide primers were designed to amplify a 130 bp fragment in the Trichoderma calmodulin (TCal) conserved sequence (forward: 5 -ACCGAAGAGCAGGTCTCTGA-3 and reverse: 5 -CTCCTTGGTGGTGATCTGG-3 ), as previously described [39]. To determine the PCR efficiency of the primer pair, a standard curve was generated using linear regression, and the Cq slope was calculated based on the Cq values for all dilutions (4 points, 10-fold dilutions from 0.1 to 100 ng) through the 7500 System software (v 1.4).…”

Molecular methods unravel the biosynthetic potential of Trichoderma species

“…3) and the epithiodioxopiperazine (ETP) gliotoxin 2. 47,50,51 Peptaibols such as 3 are linear peptides that are characterized by the occurrence of nonproteinogenic amino acids such as a-aminoisobutyrate (Aib) and a C-terminal amino alcohol, from which the name is derived. 47,52 Terpenes are considered the most abundant and chemically diverse class of natural products, with an estimated number of more than 80 000 different compounds.…”