Induction of SA-signaling pathway and ethylene biosynthesis in Trichoderma harzianum-treated tomato plants after infection of the root-knot nematode Meloidogyne incognita

Abstract

Salicylic acid-signaling pathway and ethylene biosynthesis were induced in tomato treated with Trichoderma harzianum when infected by root-knot nematodes and limited the infection by activation of SAR and ethylene production. Soil pre-treatment with Trichoderma harzianum (Th) strains ITEM 908 (T908) and T908-5 decreased susceptibility of tomato to Meloidogyne incognita, as assessed by restriction in nematode reproduction and development. The effect of T. harzianum treatments on plant defense was detected by monitoring the expression of the genes PR-1/PR-5 and JERF3/ACO, markers of the SA- and JA/ET-dependent signaling pathways, respectively. The compatible nematode-plant interaction in absence of fungi caused a marked suppression of PR-1, PR-5, and ACO gene expressions, either locally or systemically, whilst expression of JERF3 gene resulted unaffected. Conversely, when plants were pre-treated with Th-strains, over-expression of PR-1, PR-5, and ACO genes was observed in roots 5 days after nematode inoculation. JERF3 gene expression did not change in Th-colonized plants challenged with nematodes. In the absence of nematodes, Trichoderma-root interaction was characterized by the inhibition of both SA-dependent signaling pathway and ET biosynthesis, and, in the case of PR-1 and ACO genes, this inhibition was systemic. JERF3 gene expression was systemically restricted only at the very early stages of plant-fungi interaction. Data presented indicate that Th-colonization primed roots for Systemic Acquired Resistance (SAR) against root-knot nematodes and reacted to nematode infection more efficiently than untreated plants. Such a response probably involves also activation of ET production, through an augmented transcription of the ACO gene, which encodes for the enzyme catalyzing the last step of ET biosynthesis. JA signaling and Induced Systemic Resistance (ISR) do not seem to be involved in the biocontrol action of the tested Th-strains against RKNs.

Biocontrol potential ofMicrobacterium maritypicumSneb159 againstHeterodera glycines

“…Another study reported that the expression of the PR-1 gene was repressed significantly and systemically in Trichoderma harzianum-colonized plants, and the inhibition of the SA response in the host plant was probably to ensure a compatible interaction for their colonisation. 70,71 However, plants pre-treated with Sneb159 triggered an enhanced response when they were infected with H. glycines compared with the response of non-treated plants infected with H. glycines. In this study, a high expression of PR2 and PR3b in B + N was observed at 3 dpi, indicating that the SA and JA signaling pathways were activated in local resistance.…”

“…Treatment with Sneb159 suppressed the expression of PR1 , JAZ1 , and PAL at 1 and 3 dpi. Another study reported that the expression of the PR‐1 gene was repressed significantly and systemically in Trichoderma harzianum ‐colonized plants, and the inhibition of the SA response in the host plant was probably to ensure a compatible interaction for their colonisation . However, plants pre‐treated with Sneb159 triggered an enhanced response when they were infected with H. glycines compared with the response of non‐treated plants infected with H. glycines .…”

Different mechanisms of Trichoderma virens‐mediated resistance in tomato against Fusarium wilt involve the jasmonic and salicylic acid pathways

“…Many studies on growth‐promoting fungi have shown that Trichoderma spp. induce direct and indirect resistance in plants against pathogen attacks; these species are therefore recognized as key regulators of the hormone signalling pathways involved in pathogen‐associated disease resistance (Ferrigo et al ., ; Leonetti et al ., ; Martínez‐Medina et al ., ; Shoresh et al ., ; Tucci et al ., ). In the present study, TriV_JSB100 BGS treatments significantly reduced the disease level, significantly increased the JA level and up‐regulated the expression of PDF1 in WT tomato plants relative to FOL‐treated control plants (Figs a, a and a).…”

“…There have also been several reports of the involvement of JA and SA in defence responses in several crops treated with Trichoderma and challenged with pathogens (Contreras‐Cornejo et al ., ; Hermosa et al ., ; Korolev et al ., ; Martínez‐Medina et al ., ). The balance between JA and SA homeostasis is known to be important for the interaction between beneficial microbe, pathogen and host plant that results in the activation of defence signalling pathways (Contreras‐Cornejo et al ., ; Leonetti et al ., ; Martínez‐Medina et al ., ; Pieterse et al ., ). The present study revealed that BGS treatment boosted plant defences more strongly than CF treatment.…”

“…Previous studies have shown that the priming of various host plants with Trichoderma species results in the activation of multiple pathways regulated by several signalling molecules. Simultaneous induction of the salicylic acid (SA), jasmonic acid (JA) and ethylene (ET) pathways by Trichoderma species has been reported following pathogen attack in Arabidopsis thaliana (Mathys et al ., ), grape ( Vitis vinifera ) (Perazzolli et al ., ), tomato (Jogaiah et al ., ; Leonetti et al ., ; Martínez‐Medina et al ., ) and melon ( Cucumis melo ) (Martínez‐Medina et al ., ). However, extensive studies on the plant signalling mechanisms triggered by T. virens strains or its metabolites in tomato against FOL are lacking.…”