Multiple indole glucosinolates and myrosinases defend Arabidopsis against Tetranychus urticae herbivory

Arabidopsis defenses against herbivores are regulated by the jasmonate hormonal signaling pathway, which leads to the production of a plethora of defense compounds, including tryptophan-derived metabolites produced through CYP79B2/CYP79B3. Jasmonate signaling and CYP79B2/CYP79B3 limit Arabidopsis infestation by the generalist herbivore two-spotted spider mite, Tetranychus urticae. However, the phytochemicals responsible for Arabidopsis protection against T. urticae are unknown. Here, using Arabidopsis mutants that disrupt metabolic pathways downstream of CYP79B2/CYP79B3, and synthetic indole glucosinolates, we identified phytochemicals involved in the defense against T. urticae. We show that Trp-derived metabolites depending on CYP71A12 and CYP71A13 are not affecting mite herbivory. Instead, the supplementation of cyp79b2 cyp79b3 mutant leaves with the 3-indolylmethyl glucosinolate and its derived metabolites demonstrated that the indole glucosinolate pathway is sufficient to assure CYP79B2/CYP79B3-mediated defenses against T. urticae. We demonstrate that three indole glucosinolates can limit T. urticae herbivory, but that they have to be processed by the myrosinases to hinder T. urticae oviposition. Finally, the supplementation of the mutant myc2 myc3 myc4 with indole glucosinolates indicated that the transcription factors MYC2/MYC3/MYC4 induce additional indole glucosinolate-independent defenses that control T. urticae herbivory. Together, these results reveal the complexity of Arabidopsis defenses against T. urticae that rely on multiple indole glucosinolates, specific myrosinases, and additional MYC2/MYC3/MYC4-dependent defenses.