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PLANTS INTERACTING WITH OTHER ORGANISMS

Isolation and Characterization of Hydroxyproline-Rich Glycopeptide Signals in Black Nightshade Leaves^1,[OA]

Institute of Biological Chemistry, Washington State University, Pullman, Washington 99164–6340

A gene encoding a preprohydroxyproline-rich systemin, SnpreproHypSys, was identified from the leaves of black nightshade (Solanum nigrum), which is a member of a small gene family of at least three genes that have orthologs in tobacco (Nicotiana tabacum; NtpreproHypSys), tomato (Solanum lycopersicum; SlpreproHypSys), petunia (Petunia hybrida; PhpreproHypSys), potato (Solanum tuberosum; PhpreproHypSys), and sweet potato (Ipomoea batatas; IbpreproHypSys). SnpreproHypSys was induced by wounding and by treatment with methyl jasmonate. The encoded precursor protein contained a signal sequence and was posttranslationally modified to produce three hydroxyproline-rich glycopeptide signals (HypSys peptides). The three HypSys peptides isolated from nightshade leaf extracts were called SnHypSys I (19 amino acids with six pentoses), SnHypSys II (20 amino acids with six pentoses), and SnHypSys III (20 amino acids with either six or nine pentoses) by their sequential appearance in SnpreproHypSys. The three SnHypSys peptides were synthesized and tested for their abilities to alkalinize suspension culture medium, with synthetic SnHypSys I demonstrating the highest activity. Synthetic SnHypSys I was capable of inducing alkalinization in other Solanaceae cell types (or species), indicating that structural conformations within the peptides are recognized by the different cells/species to initiate signal transduction pathways, apparently through recognition by homologous receptor(s). To further demonstrate the biological relevance of the SnHypSys peptides, the early defense gene lipoxygenase D was shown to be induced by all three synthetic peptides when supplied to excised nightshade plants.

² Present address: National Research Centre on Plant Biotechnology, Lal Bahadur Shastri Building, Indian Agricultural Research Institute, New Delhi 110012, India.

³ Present address: Department of Biotechnology, National Kaohsiung Normal University, No. 62, Shenjhong Road, Yanchao Township, Kaohsiung County 824, Taiwan.

The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Gregory Pearce (pearce{at}wsu.edu).

^[OA] Open Access articles can be viewed online without a subscription.

www.plantphysiol.org/cgi/doi/10.1104/pp.109.138669

^* Corresponding author; e-mail pearce{at}wsu.edu.

Received March 13, 2009; accepted April 20, 2009; published April 29, 2009.