miR825-5p-regulated TNLs govern Arabidopsis resistance to Tetranychus urticae and Pieris brassicae

MicroRNAs are essential regulators in plant resistance to biotic stresses, but their specific roles in the plant-herbivore context require deeper investigation. Here, we studied how the Arabidopsis miR825-5p differentially modulates certain TNLs (MRT1, MRT2, and MIST1), triggering defensive responses against the sucking acari Tetranychus urticae or the chewing insect Pieris brassicae. We demonstrated that the expression of miR825-5p is downregulated following T. urticae and P. brassicae infestation and identified miRNA TNL targets whose expression is induced by both feeders. miR825-5p downregulates MRT1 and MRT2, acting as a negative modulator of Arabidopsis basal resistance against T. urticae. A similar miR825-5p-mediated regulation of basal resistance, including MRT1 and MRT2 but also MIST1 silencing, is involved in the Arabidopsis response against P. brassicae. Moreover, miR825-5p triggered the production of MIST1-derived secondary interfering RNAs (phasiRNAs) and amplified silencing of MRT1 and MRT2. Taken together, our findings reveal the role of the miR825-5p/TNL module in controlling Arabidopsis response and adapting plant defenses based on the specific threat.