Abstract
Trichoderma can induce plant hormone signal pathways mediating plant defenses, resulting in broad-spectrum resistance to phytopathogens. Herein, Malus sieversii seedlings were treated with Trichoderma biofertilizer and/or Alternaria alternata f. sp. mali, and transcriptome analysis revealed significant differential expression. There was a high similarity between the transcriptome expression profiles of Trichoderma-induced and A. alternata-infected M. sieversii samples for genes related to jasmonic acid (JA), ethylene, and salicylic acid (SA) signaling pathways. Additionally, Trichoderma biofertilizer activated numerous disease-resistant genes (ERF, NAC, bHLH, and STK) and defense response genes (DRP, ABC, and HSP). Among transcription factors, members of the ERF family were the most differentially expressed (18 ERFs), indicating that they may be closely related to defense responses. Among ERFs, differential expression of MsERF105 was the most significant (upregulated 27.6-fold compared to controls). MsERF105 was heterologously expressed in PdPap poplar (Populus davidiana × Populus alba var. pyramidalis Louche), and following infection with A. alternata (Aal), transgenic PdPap-MsERF105s plants displayed lower malondialdehyde (downregulated 41.4%) and reactive oxygen species (ROSs) levels, and higher reductase activities, especially superoxide dismutase (SOD; upregulated 77.5% compared to PdPap-ROK2 plants). Furthermore, the lesion areas of PdPap-MsERF105s leaves were significantly smaller (0.2%) than those of PdPap-ROK2 leaves (∼26.0%), and the cell membrane integrity was superior for PdPap-MsERF105s leaves. Thus, MsERF105 enhanced the resistance of PaPap poplar to Aal, presumably because MsERF105 activates the expression of PR1 and PDF1.2. In conclusion, Trichoderma biofertilizer modulated the differential expression of numerous disease resistance genes and defense response genes in M. sieversii in response to pathogen attack, and MsERF105 played important roles in this process.
Highlights
Trichoderma can penetrate and colonize plant roots, triggering plant defense responses, and is commonly used as an inducer of plant defenses against pathogens (Poveda, 2021)
M. sieversii seedlings were treated with Trichoderma biofertilizer or Alternaria alternata f. sp. mali (Aalm), and differentially expressed genes (DEGs) were analyzed by RNA sequencing (RNA-Seq)
The number of differential genes in M. sieversii treated with Trichoderma biofertilizer or Aalm was less than that following treatment with both, and more genes were upregulated than downregulated under all treatment conditions (Figure 1B)
Summary
Trichoderma can penetrate and colonize plant roots, triggering plant defense responses, and is commonly used as an inducer of plant defenses against pathogens (Poveda, 2021). 6-pentyl-alphapyrone from Trichoderma koningii induces systemic resistance in tobacco against tobacco mosaic virus (TMV), stimulates the activities of pathogenesis-related (PR) enzymes [superoxide dismutase (SOD), peroxidase (POD), and polyphenol oxidase), and upregulates the expression of defense-related genes (PR-a, PR-b, and PR-10) (Taha et al, 2021). Plants treated with Trichoderma harzianum T22 displayed overexpression of transcripts encoding several families of defense-related transcription factors (bZIP, MYB, NAC, ERF, and WRKY), suggesting that the fungus contributes to the priming of plant responses (Coppola et al, 2019). Trichoderma can trigger plant defense responses in different pathways
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