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JXB Advance Access originally published online on May 24, 2007
Journal of Experimental Botany 2007 58(8):2217-2223; doi:10.1093/jxb/erm081
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© The Author [2007]. Published by Oxford University Press [on behalf of the Society for Experimental Biology]. All rights reserved. For Permissions, please e-mail: journals.permissions@oxfordjournals.org

RESEARCH PAPER

Evidence for long-distance xylem transport of signal peptide activity from tomato roots

Peter M. Neumann*

Department of Environmental, Water and Agricultural Engineering, Faculty of Civil and Environmental Engineering, Technion IIT, Haifa 32000, Israel

* E-mail: agpetern{at}tx.technion.ac.il

Several types of small, endogenous signal peptides are now known to induce a wide range of local and systemic responses in plants, but how such signal peptide activity is transported over long distances remains unclear. In particular, the possible occurrence and root-to-shoot transport of signal peptide activity in the xylem does not appear to have been previously investigated. Suspension-cultured cells of wild tomato Lycopersicon peruvanium L. were used in an established bioassay for detecting nanomolar concentrations of signal peptides via the induction of alkalinizing activity. Xylem sap naturally exuded from the cut and washed stem-surfaces of de-topped tomato plants (Lycopersicon esculentum L. cv. Castlemart) was collected, partially purified, concentrated, and shown by the bioassay consistently to contain significant alkalinizing activity. Plant salinity treatment induced further small increases in activity. Subsidiary experiments indicated that the alkalinizing activity found in the xylem-sap had properties similar to those of known plant signal peptides and was root derived. Thus, it was (i) detectable within minutes, (ii) eluted similarly during HPLC chromatography, (iii) destroyed by incubation with proteases and stable in the presence of protease inhibitor cocktail, and (iv) not found in bioassays of simulated xylem sap placed on the cut stem-surfaces of non-exuding roots in order to detect any significant release of wound peptides from the stem. Further investigations of the signal peptide activity in root xylem sap could provide new insights into its identity, genes, receptors, origins, and possible hormonal roles in regulating shoot growth and development.

Key words: Bioactive peptides, bioassay, hormone, long-distance signal, Lycopersicon, xylem-sap

Received 19 November 2006; Revised 18 March 2007 Accepted 21 March 2007


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P. M. Neumann
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[Abstract] [Full Text] [PDF]


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