Haruta, Miyoshi , Sussman, Michael R. .
Identification of Endogenous Peptides that Cause Rapid Cytoplasmic Calcium Increases in Arabidopsis Seedlings.
To identify endogenous peptide hormones regulating cytoplasmic Ca2+, Arabidopsis seedlings expressing aequorin, a Ca2+-reporting photoprotein, was adapted as a tool for high throughput in vivo cytoplasmic Ca2+ assays. Use of this system with fractions derived from Arabidopsis extracts indicated the presence of multiple protease sensitive activities. HPLC coupled to tandem mass spectrometry was used to purify and identify the predominant active molecule as a member of the rapid alkalinization factor protein family, AtRALF1 (At1g02900). Within 40 seconds upon treatment using the peptide derived by either chemical synthesis, or purified from plants, the cytoplasmic Ca2+ level increased and reached its maximum at nanomolar concentrations. Prior treatment with a Ca2+ chelator or IP3-signal inhibitors suppressed the AtRALF1-induced Ca2+ increase, indicating the involvement of Ca2+ influx across the plasma membrane and possibly also, Ca2+ releases from intracellular sources. The AtRALF1 mRNA is observed mainly in roots. Our observations support a model in which AtRALF1-mediated cytoplasmic calcium changes regulate root cell expansion, possibly through a cell surface AtRALF1 receptor.
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1 - University of Wisconsin-Madison, Biotechnology Center, 425 Henry Mall, Madison, Wisconsin, 53706, U.S.A.
2 - University of Wisconsin-Madison, Biotechnology Center
Presentation Type: Plant Biology Abstract
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM