ARS | Publication request: A newly identified tomato peptide induces cytosolic calcium and may correspond to pathogen defense-related endogenous peptides in Arabidopsis

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: June 4, 2012
Publication Date: N/A

Technical Abstract: Plants recognize a variety of stimuli that invoke defenses against attacking pathogens and herbivores. This recognition primes the plant to mount defenses against herbivory and disease. These stimuli include molecules called damage-associated molecular patterns or DAMPs, among them signaling peptides synthesized endogenously. DAMPs are perceived by receptors in the plasma membrane which induce defense responses that are well characterized in Arabidopsis. Cytosolic calcium signals transduce the perception of DAMPs into defenses against microbial pathogens. The Arabidopsis Pep Receptors (AtPepR1 and AtPepR2) bind the AtPep signaling peptides, causing reactive oxygen species production, downstream induction of defense genes, and reduction in the spread of infection within the plants. Sequence homology of putative proteins found in tomato predicted the existence of Pep receptors similar to AtPepR. Additionally, a peptide termed Slpep was predicted in tomato which is homologous to both AtPeps and a DAMP shown to suppress disease in corn. Aequorin luminometry demonstrates experimentally that Slpep induces a cytosolic calcium signal in leaves in the minutes following exposure. This response resembles that of Arabidopsis exposed to AtPeps. Additionally, tomatoes and other plants in genus Solanum have a unique signaling pathway in which another small endogenous peptide, systemin, causes local and systemic defense responses including volatile organic compound synthesis and expression of defense-related genes in response to herbivory. Systemin also induces a rapid intracellular calcium rise, suggesting that calcium mediates these effects. Further work will characterize these tomato peptide signaling pathways to enhance our understanding of these plants’ natural defenses.