Detecting the Hormonal Pathways in Oilseed Rape behind Induced Systemic Resistance by Trichoderma harzianum TH12 to Sclerotinia sclerotiorum

Abstract

Plants have the ability to resist pathogen attack after infection or treatment with biotic and abiotic elicitors. In oilseed rape plant Brassica napus AACC and in the artificially synthesized Raphanus alboglabra RRCC, the root-colonizing Trichoderma harzianum TH12 fungus triggers induced systemic resistance (ISR), and its culture filtrate (CF) triggers a systemic acquired resistance (SAR) response against infection by the Sclerotinia sclerotiorum. Salicylic acid (SA) and jasmonic acid/ethylene (JA/ET) are plant hormone signals that play important roles in the regulation of ISR and SAR. In this study, at six different time points (1, 2, 4, 6, 8 and 10 days post-infection [dpi]), six resistance genes were used as markers of signaling pathways: JA/ET signaling used AOC3, PDF1.2 and ERF2 genes, while PR-1, TGA5 and TGA6 genes were used as markers of SA signaling. The results of quantitative real-time polymerase chain reaction (qRT-PCR) showed that AOC3, PDF1.2 and ERF2 expression levels in infected leaves of AACC and RRCC increase at 1 and 2 dpi with S. sclerotiorum or inoculation with TH12. PR-1, TGA5 and TGA6 expression levels increased at 8 and 10 dpi in infected leaves. PR-1, TGA5 and TGA6 expression levels increased early in plants treated with CF in both of the healthy genotypes. Furthermore, induction of SA- and JA/ET-dependent defense decreased disease symptoms in infected leaves at different times. The results suggest that the RRCC genotype exhibits resistance to disease and that the ability of TH12 and its CF to induce systemic resistance in susceptible and resistant oilseed rape genotypes exists. In addition, the results indicate for the first time that in RRCC the SA signaling pathway is involved in resistance to necrotrophic pathogens.

The Trichoderma harzianum Kelch Protein ThKEL1 Plays a Key Role in Root Colonization and the Induction of Systemic Defense in Brassicaceae Plants

“…In addition, overexpression of this gene in Arabidopsis plants leads to an upregulation of JA as well as SA-marker genes, although in this case this upregulation was also observed in wild type plants. These results indicate induction of systemic responses, that has also been reported against Sclerotinia sclerotiorum in B. napus after root colonization by T. harzianum (Alkooranee et al, 2017). These authors proved that this induction of systemic defense through JA/ET and SA-signaling pathways occurs at different times, that is in agreement with our results.…”

Differential expression analysis of Trichoderma virens RNA reveals a dynamic transcriptome during colonization of Zea mays roots

“…Interestingly, other endophytic fungi also repress plant SA production and have strain-dependent effects on JA [9]. Fungal effectors seem to play a large role in the mediation of SA/JA as application of T. virens spores versus filtrate to a plant hosts results in differential induction of SA or JA [12, 34]. Most research on T. virens mediation of phytohormone levels measures either the hormone level in planta or hormone-dependent gene expression as a reflection of hormone level.…”

Trichoderma parareesei Favors the Tolerance of Rapeseed (Brassica napus L.) to Salinity and Drought Due to a Chorismate Mutase

“…In our study, we have verified how the inoculation without stress of rapeseed plants with different strains of Trichoderma represents a significant increase in the weight of seeds produced by each plant (Figure 1A), something observed previously, although without knowing exactly what are the fungal mechanisms involved in it of all those described for the Trichoderma-plant interaction, with the application of T. harzianum, also increasing the weight of seeds per plant [29]; T. asperellum, with an increase in seed weight, lipid content, and total seed yield [43]; T. viride, increasing fresh and dry biomass [44]; and T. atroviride, with a significantly larger root and shoot biomass, but without a systemic induction of plant-defenses against the caterpillars Plutella xylostella [45]. However, the induction of systemic resistance in rapeseed has been observed with the rapeseed root application of T. harzianum against the leaf fungi Sclerotinia sclerotiorum [46] and Erysiphe cruciferarum [47].…”