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J. Biol. Chem., Vol. 283, Issue 17, 11469-11476, April 25, 2008

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Six Peptide Wound Signals Derived from a Single Precursor Protein in Ipomoea batatas Leaves Activate the Expression of the Defense Gene Sporamin^*

Yu-Chi Chen¹, William F. Siems, Gregory Pearce², and Clarence A. Ryan

From the Institute of Biological Chemistry and the Department of Chemistry, Washingston State University, Pullman, Washington 99164-6340

A mixture of three homologous bioactive hydroxyproline-rich glycopeptides (HypSys peptides) of 18 amino acids in length, differing only at two residues, was isolated from leaves of Ipomoea batatas, the common sweet potato. One of the peptides represented over 95% of the isolated isopeptides, which, at 2.5 nM concentration, induced the expression of sporamin, a major defense protein of I. batatas. The sequence of the major isoform was used to synthesize a primer that identified a cDNA encoding a precursor protein. The protein contained six proline-rich regions whose sequences suggested that they might be HypSys defense signals. One of the encoded peptides, called IbHypSys IV, was identical to one of two minor components of the isolated isopeptides, but neither the major isopeptide nor the other minor isoform was found within the precursor. The six peptides encoded by the precursor gene were synthesized but with hydroxyproline residues at positions found in the native isoforms and lacking carbohydrate moieties. All of the peptides were biologically active when supplied to leaves of sweet potato plants. The gene is the first ortholog of the preproHypSys gene family to be found outside of the Solanaceae family, and its encoded peptide precursor is the first example in plants of a precursor protein with six potential peptide defense signals, a scenario only found previously in animals. The data indicate that multiple copies of the HypSys peptides in a single precursor may have an important role in amplifying wound signaling in leaves in response to herbivore attacks.

Received for publication, November 1, 2007 , and in revised form, February 12, 2008.

The nucleotide sequence(s) reported in this paper has been submitted to the GenBank^TM/EBI Data Bank with accession number(s) EF621761.

^* This research was supported by National Science Foundation Grants IBN 0090766 and 0623029; National Institutes of Health Grant 1S10RR022538-01; the Charlotte Y. Martin Foundation; and the Washington State University College of Agriculture, Human and Natural Resources Sciences. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

Clarence A. "Bud" Ryan: 9/29/31-10/7/07.

¹ To whom correspondence may be addressed: Dept. of Horticulture and Biotechnology, Chinese Culture University, 55 Hwa-Kang Rd., Yangmin Shan, Taipei 111 Taiwan, R.O.C. Tel.: 886-2-2861-0511, Ext. 31132; Fax: 886-2-2861-8266; E-mail: cyq12{at}faculty.pccu.edu.tw. ² To whom correspondence may be addressed: Gregory Pearce: Institute of Biological Chemistry, WA State, University, 299 Clark Hall, Pullman, WA 99164-6340. Tel.: 509-335-4571; Fax: 509-335-7643; E-mail:pearce{at}wsu.edu.

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This article has been cited by other articles:

				G. Pearce, R. Bhattacharya, Y.-C. Chen, G. Barona, Y. Yamaguchi, and C. A. Ryan Isolation and Characterization of Hydroxyproline-Rich Glycopeptide Signals in Black Nightshade Leaves Plant Physiology, July 1, 2009; 150(3): 1422 - 1433. [Abstract] [Full Text] [PDF]