Abstract
Plants actively respond to herbivory by inducing various defense mechanisms in both damaged (locally) and non-damaged tissues (systemically). In addition, it is currently widely accepted that plant-to-plant communication allows specific neighbors to be warned of likely incoming stress (defense priming). Systemin is a plant peptide hormone promoting the systemic response to herbivory in tomato. This 18-aa peptide is also able to induce the release of bioactive Volatile Organic Compounds, thus also promoting the interaction between the tomato and the third trophic level (e.g. predators and parasitoids of insect pests). In this work, using a combination of gene expression (RNA-Seq and qRT-PCR), behavioral and chemical approaches, we demonstrate that systemin triggers metabolic changes of the plant that are capable of inducing a primed state in neighboring unchallenged plants. At the molecular level, the primed state is mainly associated with an elevated transcription of pattern -recognition receptors, signaling enzymes and transcription factors. Compared to naïve plants, systemin-primed plants were significantly more resistant to herbivorous pests, more attractive to parasitoids and showed an increased response to wounding. Small peptides are nowadays considered fundamental signaling molecules in many plant processes and this work extends the range of downstream effects of this class of molecules to intraspecific plant-to-plant communication.
Highlights
Plants have developed multiple defense strategies in a continuous co-evolution with pests
Systemin was isolated by exploiting its ability to strongly induce protease inhibitors (PIs)[6], further studies indicated that this peptide stimulates a wider transcriptome reprogramming, affecting the expression of genes involved in different hormone-regulated pathways[8]
Receiver description Tomato plants exposed to Source plants 1 (S1) (R-S1) Tomato plants exposed to Source plants 2 (S2) (R-S2) Tomato plants exposed to S3 (R-S3) Tomato plants exposed to Source plants 4 (S4) (R-S4)
Summary
Plants have developed multiple defense strategies in a continuous co-evolution with pests. On the basis of the mode of action, defense traits are distinguished in direct and indirect[1,2] The former includes, for instance, physical barriers and metabolites that directly interfere with pests, while the latter involves any plant trait that attracts natural enemies of pests, such as predators and parasitoids[1,2]. Systemin is an 18 amino acid (aa) hormone that was firstly identified as a limited range mobile inducer in the wound response in tomato[3]. This peptide is released from a 200 aa precursor, called prosystemin, which is encoded by a single-copy inducible gene[4]. Receiver description (code) Tomato plants exposed to S1 (R-S1) Tomato plants exposed to S2 (R-S2) Tomato plants exposed to S3 (R-S3) Tomato plants exposed to S4 (R-S4)
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