Novel aspinolide production by Trichoderma arundinaceum with a potential role in Botrytis cinerea antagonistic activity and plant defence priming

Abstract

Harzianum A (HA), a trichothecene produced by Trichoderma arundinaceum, has recently been described to have antagonistic activity against fungal plant pathogens and to induce plant defence genes. In the present work, we have shown that a tri5 gene-disrupted mutant that lacks HA production overproduces two polyketides, aspinolides B and C, which were not detected in the wild-type strain. Furthermore, four new aspinolides (D-G) were characterized. These compounds confirm that a terpene-polyketide cross-pathway exists in T. arundinaceum, and they may be responsible for the antifungal activity and the plant sensitization effect observed with the tri5-disrupted mutant. In addition, the molecular changes involving virulence factors in the phytopathogenic fungus Botrytis cinerea 98 (Bc98) during interaction with T. arundinaceum were investigated. The expression of genes involved in the production of botrydial by Bc98 was relatively repressed by HA, whereas other virulence genes of this pathogen were induced by the presence of T. arundinaceum, for example atrB and pg1 which encode for an ABC transporter and endopolygalacturonase 1 respectively. In addition, the interaction with Bc98 significantly repressed the production of HA by T. arundinaceum, indicating that a bidirectional transcriptional regulation is established between these two antagonistic fungi.

Involvement of Trichoderma harzianum Epl-1 Protein in the Regulation of Botrytis Virulence- and Tomato Defense-Related Genes

“…These Trichoderma spp. can exert their biocontrol activities through different mechanisms, such as mycoparasitism (Monteiro and Ulhoa, 2006; Almeida et al, 2007), the production of extracellular hydrolytic enzymes (Benítez et al, 2004; Monteiro et al, 2010), the expression of proteins involved in the competition for nutrients which provide a nutritional advantage (Elad, 2000), and the production of secondary metabolites with antifungal activity (Rubio et al, 2009; Cardoza et al, 2011; Tijerino et al, 2011; Malmierca et al, 2012, 2013, 2015). Moreover, some Trichoderma spp.…”

Botrydial and botcinins produced by Botrytis cinerea regulate the expression of Trichoderma arundinaceum genes involved in trichothecene biosynthesis

“…Botcs have a redundant role with BOT in their phytotoxicity (Pinedo et al ., ), although, based on the results presented here, they seem to have a very different function in the interaction with other environmental fungi and, more specifically, with other sesquiterpene‐producing fungi. Furthermore, the synthesis of polyketide compounds as a result of the disruption of the synthesis of sesquiterpenoid compounds has also been described in T. arundinaceum , where a block in the production of the trichothecene (sesquiterpene) HA resulted in the production at high levels of several aspinolides, polyketide compounds that are not produced or produced at low levels in the wild‐type strain (Malmierca et al ., ). Interestingly, similar cross‐pathway interactions have been described for other fungal gene clusters.…”

“…Furthermore, there are several elements that are clearly involved in this interaction. These include BOT exogenously added or produced by B05.10, Botcs added to the medium or produced by bcbot2Δ , HA produced by Ta37, other SMs produced by B05.10 (botcinic acid, Moraga et al ., ; botrylactones, Massaroli et al ., ) and Ta37 (aspinolides, Malmierca et al ., ), and the hydrolytic enzymes and signalling molecules generated in the interaction zone that can act as signals even far away from the confrontation region. The cross‐pathway interactions established between these SMs, together with the hydrolytic enzyme activity, observed in the present work, and with the ability of HA to inhibit the germination of B. cinerea spores (Malmierca et al ., ), contribute to explain why T. arundinaceum is able to overcome and suppress the virulence mechanisms exhibited by the pathogen.…”

Trichothecenes and aspinolides produced by Trichoderma arundinaceum regulate expression of Botrytis cinerea genes involved in virulence and growth

“…), which does not show in vivo phytotoxicity (Malmierca et al , ). In previous works we observed that the disruption of the trichodiene synthase encoding gene ( tri5 ) (strain TaΔTri5) blocked the production of HA and reduced the biocontrol potential against B. cinerea (Malmierca et al , ), but also resulted in the production of high levels of aspinolides (Asp) B and C (Malmierca et al , ) (Fig. ).…”

“…). Among these polyketide compounds, AspC showed antifungal activity against B. cinerea (Malmierca et al , ). Although the culture broth of TaΔTri5 failed to prevent tomato leaf lesion formation by B. cinerea , the size of the lesions was reduced due to the antifungal activity of AspC (Malmierca et al , ).…”