Abstract

Systemin is a signal peptide that promotes the response to wounding and herbivore attack in tomato. This 18-amino acid peptide is released from a larger precursor, prosystemin. To study the role of systemin as a modulator of defense signaling, we generated tomato (Solanum lycopersicum) transgenic plants that overexpress the prosystemin cDNA. We carried out a transcriptomic analysis comparing two different transgenic events with the untransformed control. The Gene Ontology categories of the 503 differentially expressed genes indicated that several biological functions were affected. Systemin promotes the expression of an array of defense genes that are dependent on different signaling pathways and it downregulates genes connected with carbon fixation and carbohydrate metabolism. These alterations present a degree of overlap with the response programs that are classically associated to pathogen defense or abiotic stress protection, implying that end products of the systemin signaling pathway may be more diverse than expected. We show also that the observed transcriptional modifications have a relevant functional outcome, since transgenic lines were more resistant against very different biotic stressors such as aphids (Macrosiphum euphorbiae), phytopathogenic fungi (Botrytis cinerea and Alternaria alternata) and phytophagous larvae (Spodoptera littoralis). Our work demonstrated that in tomato the modulation of a single gene is sufficient to provide a wide resistance against stress by boosting endogenous defense pathways. Overall, the data provided evidence that the systemin peptide might serve as DAMP signal in tomato, acting as a broad indicator of tissue integrity.Electronic supplementary materialThe online version of this article (doi:10.1007/s11105-014-0834-x) contains supplementary material, which is available to authorized users.

Highlights

  • Plants have evolved a variety of defense mechanisms against biotic stress, including chemical compounds, physical barriers, and indirect defenses that entail the recruitment of predators and parasitoids (Wu and Baldwin 2010)

  • Recent progress has revealed that biotic stress can generate larger than expected sets of differentially expressed genes, which usually include a significant proportion of sequences that do not code for proteins directly involved in plant defense (Bilgin et al 2010; Coppola et al 2013; De Vos et al 2005; Kerchev et al 2012; Thompson and Goggin 2006)

  • Considering that the hybrid tomato cultivar “Better Boy” that was originally transformed with a construct overexpressing prosystemin cDNA (Mcgurl et al 1994) is a VFN variety, we used as a recipient a susceptible genotype, the “Red Setter” variety, more appropriate to study systemin effect on biotic stresses

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Summary

Corrado Rao

The data provided evidence that the systemin peptide might serve as DAMP signal in tomato, acting as a broad indicator of tissue integrity

Introduction
Materials and Methods
Results
Discussion
Full Text
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