Calcium-Dependent Protein Phosphorylation May Mediate the Gibberellic Acid Response in Barley Aleurone¹

Sian Ritchie and Simon Gilroy^*

Biology Department, The Pennsylvania State University, 208 Mueller Laboratory, University Park, Pennsylvania 16802

Peptide substrates of well-defined protein kinases were microinjected into aleurone protoplasts of barley (Hordeum vulgare L. cv Himalaya) to inhibit, and therefore identify, protein kinase-regulated events in the transduction of the gibberellin (GA) and abscisic acid signals. Syntide-2, a substrate designed for Ca²⁺- and calmodulin (CaM)-dependent kinases, selectively inhibited the GA response, leaving constitutive and abscisic acid-regulated events unaffected. Microinjection of syntide did not affect the GA-induced increase in cytosolic [Ca²⁺], suggesting that it inhibited GA action downstream of the Ca²⁺ signal. When photoaffinity-labeled syntide-2 was electroporated into protoplasts and cross-linked to interacting proteins in situ, it selectively labeled proteins of approximately 30 and 55 kD. A 54-kD, soluble syntide-2 phosphorylating protein kinase was detected in aleurone cells. This kinase was activated by Ca²⁺ and was CaM independent, but was inhibited by the CaM antagonist N-(6-aminohexyl)-5-chloro-1-naphthalene-sulfonamide (250 µm), suggesting that it was a CaM-domain protein kinase-like activity. These results suggest that syntide-2 inhibits the GA response of the aleurone via an interaction with this kinase, implicating the 54-kD kinase as a Ca²⁺-dependent regulator of the GA response in these cells.

Plant Physiol. (1998) 116: 765-776
Copyright Clearance Center:   0032-0889/98/116/0765/12
© 1998 American Society of Plant Physiologists

This article has been cited by other articles:

				G. M. Yoon, P. E. Dowd, S. Gilroy, and A. G. McCubbin Calcium-Dependent Protein Kinase Isoforms in Petunia Have Distinct Functions in Pollen Tube Growth, Including Regulating Polarity PLANT CELL, April 1, 2006; 18(4): 867 - 878. [Abstract] [Full Text] [PDF]

				Y.-s. Hwang, P. C. Bethke, Y. H. Cheong, H.-S. Chang, T. Zhu, and R. L. Jones A Gibberellin-Regulated Calcineurin B in Rice Localizes to the Tonoplast and Is Implicated in Vacuole Function Plant Physiology, July 1, 2005; 138(3): 1347 - 1358. [Abstract] [Full Text] [PDF]

				A. K. Azad, Y. Sawa, T. Ishikawa, and H. Shibata Phosphorylation of Plasma Membrane Aquaporin Regulates Temperature-Dependent Opening of Tulip Petals Plant Cell Physiol., May 1, 2004; 45(5): 608 - 617. [Abstract] [Full Text] [PDF]

				S. C. Chang, M. H. Cho, S.-K. Kim, J. S. Lee, A. Kirakosyan, and P. B. Kaufman Changes in phosphorylation of 50 and 53 kDa soluble proteins in graviresponding oat (Avena sativa) shoots J. Exp. Bot., March 1, 2003; 54(384): 1013 - 1022. [Abstract] [Full Text] [PDF]

				M. L. Martín and L. Busconi A Rice Membrane-Bound Calcium-Dependent Protein Kinase Is Activated in Response to Low Temperature Plant Physiology, March 1, 2001; 125(3): 1442 - 1449. [Abstract] [Full Text]

				V. S. Anil, A. C. Harmon, and K. S. Rao Spatio-Temporal Accumulation and Activity of Calcium-Dependent Protein Kinases during Embryogenesis, Seed Development, and Germination in Sandalwood Plant Physiology, April 1, 2000; 122(4): 1035 - 1044. [Abstract] [Full Text]

				E. van der Knaap, W.-Y. Song, D.-L. Ruan, M. Sauter, P. C. Ronald, and H. Kende Expression of a Gibberellin-Induced Leucine-Rich Repeat Receptor-Like Protein Kinase in Deepwater Rice and Its Interaction with Kinase-Associated Protein Phosphatase Plant Physiology, June 1, 1999; 120(2): 559 - 570. [Abstract] [Full Text]

				A. Moutinho, A. J. Trewavas, and R. Malhó Relocation of a Ca2+-Dependent Protein Kinase Activity during Pollen Tube Reorientation PLANT CELL, September 1, 1998; 10(9): 1499 - 1510. [Abstract] [Full Text]

				S. X. Lu and E. M. Hrabak An Arabidopsis Calcium-Dependent Protein Kinase Is Associated with the Endoplasmic Reticulum Plant Physiology, March 1, 2002; 128(3): 1008 - 1021. [Abstract] [Full Text] [PDF]