Abstract
Acibenzolar-S-methyl (ASM) is a chemical compound, which is able to induce resistance in several model and non-model plants, but the end-players of this induced defense remain ill-defined. Here, we test the hypothesis that treatment with ASM can protect apple (Malus × domestica) against the rosy apple aphid (Dysaphis plantaginea) and investigate the defense molecules potentially involved in resistance. We measured aphid life traits and performed behavioral assays to study the effect of ASM on plant resistance against the aphid, and then combined transcriptomic, bioinformatics, metabolic and biochemical analyses to identify the plant compounds involved in resistance. Plants treated with ASM negatively affected several life traits of the aphid and modified its feeding and host seeking behaviors. ASM treatment elicited up-regulation of terpene synthase genes in apple and led to the emission of (E,E)-α-farnesene, a sesquiterpene that was repellent to the aphid. Several genes encoding amaranthin-like lectins were also strongly up-regulated upon treatment and the corresponding proteins accumulated in leaves, petioles and stems. Our results link the production of specific apple proteins and metabolites to the antibiosis and antixenosis effects observed against Dysaphis plantaginea, providing insight into the mechanisms underlying ASM-induced herbivore resistance.
Highlights
Acibenzolar-S-methyl (ASM, called benzo-1,2,3-thiadiazole-7-carbothioic acid S-methyl ester or BTH) is a well-known functional analog of salicylic acid (SA), inducing resistance in a number of plant species against a wide range of plant pathogens, at least under controlled conditions (Thakur and Sohal, 2013; Walters et al, 2013)
We identified two strongly up-regulated gene families coding for proteins with a potential to modify Dysaphis plantaginea biology and explored their role in resistance by antibiosis and antixenosis: genes of the terpenesynthesis pathway, leading to modified volatile emission, and genes of the lectin family, which could interfere during aphid feeding
Dysaphis plantaginea Life Traits Are Affected in ASM-Treated Plants
Summary
Acibenzolar-S-methyl (ASM, called benzo-1,2,3-thiadiazole-7-carbothioic acid S-methyl ester or BTH) is a well-known functional analog of salicylic acid (SA), inducing resistance in a number of plant species against a wide range of plant pathogens, at least under controlled conditions (Thakur and Sohal, 2013; Walters et al, 2013). Induced resistance against aphids merits further investigations, especially as plant resistance to aphids involves salicylate and jasmonate signals as well as subsequent signaling crosstalks (Smith and Chuang, 2014) This is true for ASM against the apple rosy aphid (Dysaphis plantaginea) due to the known effect of this particular compound against apple scab and fire blight. Two stages of the life cycle are important as targets for control methods: (i) fundatrigeniae on apple during spring, because of their massive parthenogenetic reproduction, causing severe damage, and (ii) winged gynoparae females developing in the fall on plantain, because they migrate toward apple and obviously influence the number of overwintering eggs that will be layed. We identified two strongly up-regulated gene families coding for proteins with a potential to modify Dysaphis plantaginea biology and explored their role in resistance by antibiosis (affecting life traits) and antixenosis (affecting behavior): genes of the terpenesynthesis pathway, leading to modified volatile emission, and genes of the lectin family, which could interfere during aphid feeding
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