Assistant Professor University of Washington Seattle, Washington
Body of Abstract: Tetranychus urticae (two-spotted spider mite) is an extreme generalist herbivore with the ability to feed on over 1100 plant species, including 150 of agricultural importance. The two-spotted spider mite’s polyphagous nature is driven by rapid adaptation to plant defenses. However, the specific plant defense compounds mites must overcome to achieve a host-adapted state are largely unknown. Arabidopsis thaliana is a challenging and non-preferred host for T. urticae, making it an excellent model to study mite-host adaptation. It has previously been shown that a class of tryptophan-derived compounds specific to the Brassicaceae family, indole glucosinolates, contribute partially to the A. thaliana defense response. The remaining phytochemicals that protect the plant against mite herbivory are unknown. We used combined metabolomic and transcriptomic approaches to identify classes of plant compounds that are induced upon mite feeding. HPLC-MS and RNA-seq revealed that both phenylpropanoids and flavonoids increase are induced in planta upon mite feeding. Next, we measured mite fecundity on mutant A. thaliana plants defective in overall phenylpropanoid and flavonoid biosynthesis to assess mite performance. We found that mite fecundity significantly increases on phenylpropanoid and flavonoid mutants relative to wild-type plants, suggesting that compounds within these pathways are toxic to spider mites. We will next feed mites with these plant compounds and screen for resulting mite mortality levels to confirm the toxicity of these compounds in vivo. This study may identify phenylpropanoids and flavonoids as novel defense compounds protecting A. thaliana against spider mite herbivory. Because many phenylpropanoids and flavonoids are ubiquitous among plants, this study may shed light on mite adaptation mechanisms to not only A. thaliana, but economically important plants as well. Additionally, these findings may enable the development of novel pest control strategies through the identification of toxic phytochemicals.
