Abstract
There is no doubt that Trichoderma is an inhabitant of the rhizosphere that plays an important role in how plants interact with the environment. Beyond the production of cell wall degrading enzymes and metabolites, Trichoderma spp. can protect plants by inducing faster and stronger immune responses, a mechanism known as priming, which involves enhanced accumulation of dormant cellular proteins that function in intracellular signal amplification. One example of these proteins is the mitogen-activated protein kinases (MAPK) that are triggered by the rise of cytosolic calcium levels and cellular redox changes following a stressful challenge. Transcription factors such as WRKYs, MYBs, and MYCs, play important roles in priming as they act as regulatory nodes in the transcriptional network of systemic defence after stress recognition. In terms of long-lasting priming, Trichoderma spp. may be involved in plants epigenetic regulation through histone modifications and replacements, DNA (hypo)methylation, and RNA-directed DNA methylation (RdDM). Inheritance of these epigenetic marks for enhanced resistance and growth promotion, without compromising the level of resistance of the plant’s offspring to abiotic or biotic stresses, seems to be an interesting path to be fully explored.
Highlights
This would indicate that: (i) in the first hours of interaction with Trichoderma, JA levels are high, in an attempt to counteract the activation of salicylic acid (SA)-dependent defences, and MYB51 is not being negatively regulated by MYC2; and (ii) ERF4 acts as a transcriptional repressor of the SA-mediated suppression of JA-responsive genes, as SA levels would be being restored while maintaining a JA-dependent defence [98]
During the study in which we described that T. atroviride was able to colonize tomato roots by making the plant adapt its systemic SA- and JA-dependent defences according to the root-knot nematode (RKN) M. javanica infection stage, we observed that the first generation (F1 ) of
Just to mention one example, we have found that several miRNAs targeted to genes related to auxin, root growth, and defence were up-regulated in T. atroviride
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Trichoderma spp. can act as indirect biocontrol agents by activating systemic immune responses in a coordinated way [10], resulting in faster and stronger induction of plant basal resistance mechanisms upon the perception of a later triggering stimulus. Can act as indirect biocontrol agents by activating systemic immune responses in a coordinated way [10], resulting in faster and stronger induction of plant basal resistance mechanisms upon the perception of a later triggering stimulus This phenomenon is known as priming of defence [11] and Trichoderma can provide the plant with long-lasting resistance against biotic and abiotic stresses by balancing the different phytohormonedependent pathways—among which salicylic acid (SA), jasmonates (JA), ethylene (ET), abscisic acid (ABA), auxin (indole-3-acetic acid: IAA), and gibberellins (GA) are the most relevant—and modulating the levels of growth and defence regulatory proteins [12]. Based on our own and other authors’ experimental evidence, we want to present how plants respond to the stimuli caused by Trichoderma, stressing that such responses are transmitted onto the progeny, in terms of different types of defence, acclimation, and growth control
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