A novel double-stranded RNA mycovirus isolated from Trichoderma harzianum

Abstract

Background Trichoderma spp. are used extensively in agriculture as biological control agents to prevent soil-borne plant diseases. In recent years, mycoviruses from fungi have attracted increasing attention due to their effects on their hosts, but Trichoderma mycoviruses have not been the subject of extensive study. We sought to discover novel mycoviruses from Trichoderma spp. and to determine the effects of the biocontrol function of Trichoderma spp. Methods Mycoviruses were screened by dsRNA extraction and metagenomic analysis. RT-PCR, 5′ RACE, and 3′ RACE were used to obtain the genome sequence. MEGA software was used to classify the new mycovirus. The effects of the identified mycovirus on the biological properties of the host strain 525 were evaluated using cucumber plants and Fusarium oxysporum f. sp. cucumerinum. Results A novel mycovirus, Trichoderma harzianum mycovirus 1 (ThMV1) (accession number MH155602), was discovered in Trichoderma harzianum strain 525, a soil-borne fungus collected from Inner Mongolia, China. The mycovirus exhibited a double-stranded RNA (dsRNA) genome with a complete genome sequence of 3160 base pairs and two open reading frames (ORFs) on the negative strand. Phylogenetic analysis indicated that it belongs to an unclassified family of dsRNA mycoviruses. The removal of ThMV1 from the host 525 strain reduced host biomass production and improved the biocontrol capability of the host for Fusarium oxysporum f. sp. cucumerinum. At same time, the presence of ThMV1 improved the growth of cucumber. Conclusion ThMV1 is a new unclassified mycovirus found in T. harzianum. It not only affects the phenotype of the host strain but also reduces its biocontrol function, which sheds light on the interaction between the mycovirus and Trichoderma spp.

Coming-of-Age Characterization of Soil Viruses: A User’s Guide to Virus Isolation, Detection within Metagenomes, and Viromics

“…Mycoviruses have been identified in all major taxa of fungi, they predominantly have dsRNA genomes (although both ssRNA and ssDNA genome types exist), and for many no encapsidated extracellular states are known [58,112]. Mycovirus genomes can be isolated or otherwise identified by extracting all of the RNA from growing fungi [113] or instead using RT-PCR to target known mycovirus DNA sequences [114,115].…”

The Newly Identified Trichoderma harzianum Partitivirus (ThPV2) Does Not Diminish Spore Production and Biocontrol Activity of Its Host

“…Interestingly, the dsRNAs carry the same 5’ terminal sequence (GCCUUUUUGUCUCA), strongly suggesting the same origin of both RNAs. The sequence elements may serve as promoter recognition sites for the viral RNA-dependent RNA polymerase (RdRp) [ 20 ].…”

“…The washed mycelium was protoplasted with lysing enzyme (20 mg/mL) from Trichoderma (BingDa Biotechnology Company, Beijing, China), as described [ 20 ]. Protoplasts were adjusted to a density of 10 3 cells/mL in 1 M Tris-HCl, pH 8.2, containing 1.2 M sorbitol and 1 M CaCl 2 (TSC) and allowed to regenerate at 28 °C for 2 days [ 20 ]. Individual colonies were selected and further cultured on potato dextrose agar (PDA) at 28 °C for 5 days.…”

“…Complete genome sequencing of dsRNA viruses from T. atroviride NFCF394 and T. harzianum NFCF319 identified Trichoderma atroviride partitivirus 1 (TaPV1) and Trichoderma harzianum partitivirus 1 (ThPV1) as novel mycoviruses of the family of Partitiviridae [ 16 , 17 ]. More recently, five novel mycoviruses, i.e., Trichoderma asperellum dsRNA virus 1 (TaRV1) [ 18 ], Trichoderma harzianum mycovirus 1 (ThMBV1) [ 19 ], Trichoderma harzianum mycovirus 1 (ThMV1) [ 20 ], Trichoderma harzianum hypovirus 1 (ThHV1) [ 21 ], and the new (+)ss RNA hypovirus Trichoderma harzianum hypovirus 2 (ThHV2) [ 22 ], were identified.…”

Molecular Characterization of a Novel Mycovirus Infecting the Entomopathogenic Fungus Beauveria Bassiana

“…A series of bipartite mycoviruses, an unassigned group, have been identi ed from various fungi that consist of two double-stranded RNA (dsRNA) segments, where the RdRP sequences have more similarity to the RdRPs of proposed Unirnaviruses (mono-segment genomes) than partitiviruses (two-segment genomes). To data, 23 bipartite mycovirus have been reported including Cryphonectria parasitica bipartite mycovirus 1, Lactarius rufus RNA virus 1, and Penicillium aurantiogriseum bipartite virus 1et al [8][9][10][11].…”