Tomato systemin

Orozco-Cardenas ML, Narvaez-Vasquez J, Ryan CA (2001) Hydrogen peroxide acts as a second messenger for the induction of defense genes in tomato plants in response to wounding, systemin, and methyl jasmonate. Plant Cell 13 179-191 Palmer CJ, Anders TL, Carpenter LJ, Ktipper FC, McFiggans G (2005) Iodine and halocarbon response of Laminaria digitata to oxidative stress and links to atmospheric new particle production. Environ Chem 2 282-290... 

In tomato and potato plants, two families of Pis have been identified that show wound-inducible expression. Within 48 h after wounding of leaves of these plants, up to 2% of leaf protein content is made up of protease inhibitors. Potato type I (Potl) inhibitors are not only expressed in wounded leaves but also in tissue of leaves away from the site of attack. ° This finding prompted the search for a hormone or inducing factor that carries the signal for enhanced inhibitor expression through the plant system. Systemin, an 18-residue peptide hormone, has since been reported to induce more than 15 genes of defense nature in tomatoes. ... 

Fig. (1). The wound response in tomato plants. Tomato plants respond to wounding with the transcriptional activation and accumulation of Systemic Wound Response Proteins including defense proteins, proteolysis-associated proteins, signaling-associated proteins, and proteins of yet unknown function in plants defense. The change in gene expression can be monitored on SDS-PAGE gels. In comparison to control plants (I), treatment with systemin (II), or overexpression of the prosystemin cDNA (III) leads to the accumulation of SWRPs (arrowheads) and the downregulation of other, unidentified proteins (triangles). The figure was modified after [13].

Sequence analysis of the defense gene-inducing principle isolated from tomato leaves revealed the amino acid sequence AVQSKPPSKRDPPK-MQTD as the primary structure of systemin (Fig. (2)). The most salient... 

Fig. (2). The primary structure of tomato (pro)systemin. The amino acid sequence deduced from the prosystemin cDNA is shown. The systemin precursor comprises 200 amino acids. The 18 amino acids of the systemin oligopeptide (bold, underlined) are located close to the carboxy terminus.

Progress was made possible by use of a different source for membrane preparations. It had been shown by Felix and Boiler [26] that cell suspension cultures of a wild tomato species (Lycopersicon peruvianum) give a characteristic response to systemin. After addition of systemin an alkalinization of the culture medium was observed paralleled by an efflux of K+. Systemin also caused an increase in the activities of 1-... 

Another putative hormone involved in pathogen resistance in plants is the peptide systemin [104] (Fig. If). This 18-amino acid peptide is produced from a much longer precursor, called prosystemin, upon wounding of tomato leaves, and induces proteinase inhibitors I and II in adjacent leaves. Wounding also induces the synthesis of the precursor, prosystemin. Systemin overproduction by roots induces the proteinase inhibitors constitutively in all parts of the plant, while the antisense gene for prosystemin inhibits the development of pathogen resistance [105]. The action of systemin may be via synthesis of JA, which acts as a second messenger in the induction of the proteinase inhibitors [104]. 

Systemin appears to fit the definition of a hormone in tomato plants, where its movement from a damaged leaf to an intact leaf has been demonstrated [106]. However, since systemin has not yet been found in other plants, its generality as a hormone is still in doubt [104],... 

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