Agrobacterium tumefaciens-mediated transformation of SOD gene to Trichoderma harzianum

Strain improvement of Trichoderma harzianum for enhanced biocontrol capacity: Strategies and prospects

In the control of plant diseases, biocontrol has the advantages of being efficient and safe for human health and the environment. The filamentous fungus Trichoderma harzianum and its closely related species can inhibit the growth of many phytopathogenic fungi, and have been developed as commercial biocontrol agents for decades. In this review, we summarize studies on T. harzianum species complex from the perspective of strain improvement. To elevate the biocontrol ability, the production of extracellular proteins and compounds with antimicrobial or plant immunity-eliciting activities need to be enhanced. In addition, resistance to various environmental stressors should be strengthened. Engineering the gene regulatory system has the potential to modulate a variety of biological processes related to biocontrol. With the rapidly developing technologies for fungal genetic engineering, T. harzianum strains with increased biocontrol activities are expected to be constructed to promote the sustainable development of agriculture.

Generation of Epichloë Strains Expressing Fluorescent Proteins Suitable for Studying Host-Endophyte Interactions and Characterisation of a T-DNA Integration Event

Methods for the identification and localisation of endophytic fungi are required to study the establishment, development, and progression of host-symbiont interactions, as visible reactions or disease symptoms are generally absent from host plants. Fluorescent proteins have proved valuable as reporter gene products, allowing non-invasive detection in living cells. This study reports the introduction of genes for two fluorescent proteins, green fluorescent protein (GFP) and red fluorescent protein, DsRed, into the genomes of two distinct perennial ryegrass (Lolium perenne L.)-associated Epichloë endophyte strains using A. tumefaciens-mediated transformation. Comprehensive characterisation of reporter gene-containing endophyte strains was performed using molecular genetic, phenotypic, and bioinformatic tools. A combination of long read and short read sequencing of a selected transformant identified a single complex T-DNA insert of 35,530 bp containing multiple T-DNAs linked together. This approach allowed for comprehensive characterisation of T-DNA integration to single-base resolution, while revealing the unanticipated nature of T-DNA integration in the transformant analysed. These reporter gene endophyte strains were able to establish and maintain stable symbiotum with the host. In addition, the same endophyte strain labelled with two different fluorescent proteins were able to cohabit the same plant. This knowledge can be used to provide the basis to develop strategies to gain new insights into the host-endophyte interaction through independent and simultaneous monitoring in planta throughout its life cycle in greater detail.

Agrobacterium tumefaciens mediated transformation of ChiV gene to Trichoderma harzianum

As a soil-borne filamentous fungus, Trichoderma harzianum exhibits biological control properties because it parasitizes a large variety of phytopathogenic fungi. In this study, the vectors pBI121 and pCAMBIA1301 and cloning vector pUC18 were used to successfully construct expression vector pCA-GChiV for filamentous fungi transformation mediated by Agrobacterium tumefaciens.The ChiV gene was successfully transferred into the biocontrol fungus T. harzianum with an efficiency of 90-110 transformants per 10(7) spores using A. tumefaciens-mediated transformation. Putative transformants were analyzed to test the transformation by the southern blot, and the expression of ChiV was detected by reverse transcription PCR. The transformants were co-cultured to assay antifungal activities with Rhizoctonia solani. The inhibition rates of the transformants and no ChiV gene transferred T. harzianum were 98.56% and 82.42%, respectively, on the fourth day.The results showed that the ChiV transformants had significantly higher inhibition activity.