Electronic Thesis and Dissertation Repository

Thesis Format

Monograph

Degree

Master of Science

Program

Biology

Supervisor

Grbic, Vojislava

2nd Supervisor

Bernards, Mark

Co-Supervisor

Abstract

Tetranychus urticae – the two-spotted spider mite (TSSM) – is an extreme composite plant generalist that employs xenobiotic detoxification alongside short generational life cycles to quickly establish high performance on initially unfavorable plant hosts. I investigated the role that phenylpropanoids, a class of plant metabolites, play in Arabidopsis defense against mite herbivory. Using TSSMs adapted to Arabidopsis (Arabidopsis-adapted) and an ancestral population adapted to bean (bean-adapted) I assessed the toxicity of common (between Arabidopsis and bean) and Arabidopsis specific phenylpropanoids to TSSMs. I show that sinapoyl malate, an Arabidopsis specific phenylpropanoid, is acaricidal and exclusively reduces bean-adapted TSSM fecundity. An untargeted metabolomic analysis of bean- and Arabidopsis-adapted TSSMs treated with sinapoyl malate revealed conserved TSSM responses. I identified sinapoyl malate derivatives, such as sinapoyl glucose, that accumulate in mites following treatment with sinapoyl malate. This allowed me to reconstitute a TSSM detoxification pathway implicating TSSM enzymes, like esterases and UGTs, in sinapoyl malate metabolism.

Summary for Lay Audience

The two-spotted spider mite feeds on many important crops across the world. Farmers struggle to deal with these pests as spider mites can quickly move from one plant host to another, even when initially unfavorable to do so. Spider mites can do this by overcoming plant defenses, such as chemical defenses. However, we do not know how spider mites overcome all plant chemical defenses or how many chemical defenses are used by plants against spider mites. I am investigating if phenylpropanoids, a group of plant compounds, are chemical defenses that spider mites can overcome when moving between plant hosts. I show that the phenylpropanoid sinapoyl malate is toxic to spider mites and reduces spider mite egg laying. I also show that spider mites may detoxify sinapoyl malate by turning toxic sinapoyl malate into non-toxic products. This has allowed me to create a model detoxification pathway to explain what happens to sinapoyl malate after being ingested by spider mites. Future experiments can use this model to investigate if spider mite enzymes are involved in sinapoyl malate metabolism.

Included in

Biology Commons

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