Abstract
The cereal aleurone functions during germination by secreting hydrolases, mainly alpha-amylase, into the starchy endosperm. Multiple signal transduction pathways exist in cereal aleurone cells that enable them to modulate hydrolase production in response to both hormonal and environmental stimuli. Gibberellic acid (GA) promotes hydrolase production, whereas abscisic acid (ABA), hypoxia, and osmotic stress reduce amylase production. In an effort to identify the components of transduction pathways in aleurone cells, we have investigated the effect of okadaic acid (OA), a protein phosphatase inhibitor, on stimulus-response coupling for GA, ABA, and hypoxia. We found that OA (100 nM) completely inhibited all the GA responses that we measured, from rapid changes in cytosolic Ca2+ through changes in gene expression and accelerated cell death. OA (100 nM) partially inhibited ABA responses, as measured by changes in the level of PHAV1, a cDNA for an ABA-induced mRNA in barley. In contrast, OA had no effect on the response to hypoxia, as measured by changes in cytosolic Ca2+ and by changes in enzyme activity and RNA levels of alcohol dehydrogenase. Our data indicate that OA-sensitive protein phosphatases act early in the transduction pathway of GA but are not involved in the response to hypoxia. These data provide a basis for a model of multiple transduction pathways in which the level of cytosolic Ca2+ is a key point of convergence controlling changes in stimulus-response coupling.
Full Text
The Full Text of this article is available as a PDF (2.3 MB).
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- AbuBakar S., Boldogh I., Albrecht T. Human cytomegalovirus stimulates arachidonic acid metabolism through pathways that are affected by inhibitors of phospholipase A2 and protein kinase C. Biochem Biophys Res Commun. 1990 Jan 30;166(2):953–959. doi: 10.1016/0006-291x(90)90903-z. [DOI] [PubMed] [Google Scholar]
- Ariño J., Pérez-Callejón E., Cunillera N., Camps M., Posas F., Ferrer A. Protein phosphatases in higher plants: multiplicity of type 2A phosphatases in Arabidopsis thaliana. Plant Mol Biol. 1993 Feb;21(3):475–485. doi: 10.1007/BF00028805. [DOI] [PubMed] [Google Scholar]
- Berridge M. J. Inositol trisphosphate and calcium signalling. Nature. 1993 Jan 28;361(6410):315–325. doi: 10.1038/361315a0. [DOI] [PubMed] [Google Scholar]
- Bethke P. C., Jones R. L. Ca2+-Calmodulin Modulates Ion Channel Activity in Storage Protein Vacuoles of Barley Aleurone Cells. Plant Cell. 1994 Feb;6(2):277–285. doi: 10.1105/tpc.6.2.277. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Bradford M. M. A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of protein-dye binding. Anal Biochem. 1976 May 7;72:248–254. doi: 10.1016/0003-2697(76)90527-3. [DOI] [PubMed] [Google Scholar]
- Bush D. S., Cornejo M. J., Huang C. N., Jones R. L. Ca-stimulated secretion of alpha-amylase during development in barley aleurone protoplasts. Plant Physiol. 1986 Oct;82(2):566–574. doi: 10.1104/pp.82.2.566. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Chrispeels M. J., Varner J. E. Hormonal control of enzyme synthesis: on the mode of action of gibberellic Acid and abscisin in aleurone layers of barley. Plant Physiol. 1967 Jul;42(7):1008–1016. doi: 10.1104/pp.42.7.1008. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Deikman J., Jones R. L. Control of alpha-amylase mRNA accumulation by gibberellic Acid and calcium in barley aleurone layers. Plant Physiol. 1985 May;78(1):192–198. doi: 10.1104/pp.78.1.192. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Fadeel A., Moll B. A., Jones R. L. Effect of temperature on the synthesis and secretion of alpha-amylase in barley aleurone layers. Plant Physiol. 1980 Sep;66(3):466–470. doi: 10.1104/pp.66.3.466. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Hanson A. D., Jacobsen J. V. Control of lactate dehydrogenase, lactate glycolysis, and alpha-amylase by o(2) deficit in barley aleurone layers. Plant Physiol. 1984 Jul;75(3):566–572. doi: 10.1104/pp.75.3.566. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Hardie D. G., Haystead T. A., Sim A. T. Use of okadaic acid to inhibit protein phosphatases in intact cells. Methods Enzymol. 1991;201:469–476. doi: 10.1016/0076-6879(91)01042-z. [DOI] [PubMed] [Google Scholar]
- Hubbard M. J., Cohen P. Targeting subunits for protein phosphatases. Methods Enzymol. 1991;201:414–427. doi: 10.1016/0076-6879(91)01038-4. [DOI] [PubMed] [Google Scholar]
- Huttly A. K., Martienssen R. A., Baulcombe D. C. Sequence heterogeneity and differential expression of the alpha-Amy2 gene family in wheat. Mol Gen Genet. 1988 Oct;214(2):232–240. doi: 10.1007/BF00337716. [DOI] [PubMed] [Google Scholar]
- Irish E. E., Schwartz D. Activation of low and null activity isozymes of maize alcohol dehydrogenase by antibodies. Mol Gen Genet. 1987 Jun;208(1-2):271–278. doi: 10.1007/BF00330453. [DOI] [PubMed] [Google Scholar]
- Jones R. L., Armstrong J. E. Evidence for osmotic regulation of hydrolytic enzyme production in germinating barley seeds. Plant Physiol. 1971 Aug;48(2):137–142. doi: 10.1104/pp.48.2.137. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Jones R. L., Jacobsen J. V. Regulation of synthesis and transport of secreted proteins in cereal aleurone. Int Rev Cytol. 1991;126:49–88. doi: 10.1016/s0074-7696(08)60682-8. [DOI] [PubMed] [Google Scholar]
- Li W., Assmann S. M. Characterization of a G-protein-regulated outward K+ current in mesophyll cells of vicia faba L. Proc Natl Acad Sci U S A. 1993 Jan 1;90(1):262–266. doi: 10.1073/pnas.90.1.262. [DOI] [PMC free article] [PubMed] [Google Scholar]
- MacKintosh C., Cohen P. Identification of high levels of type 1 and type 2A protein phosphatases in higher plants. Biochem J. 1989 Aug 15;262(1):335–339. doi: 10.1042/bj2620335. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Meyer K., Leube M. P., Grill E. A protein phosphatase 2C involved in ABA signal transduction in Arabidopsis thaliana. Science. 1994 Jun 3;264(5164):1452–1455. doi: 10.1126/science.8197457. [DOI] [PubMed] [Google Scholar]
- Mitchell L. E., Dennis E. S., Peacock W. J. Molecular analysis of an alcohol dehydrogenase (Adh) gene from chromosome 1 of wheat. Genome. 1989 Jun;32(3):349–358. doi: 10.1139/g89-454. [DOI] [PubMed] [Google Scholar]
- Moll B. A., Jones R. L. Alpha-amylase secretion by single barley aleurone layers. Plant Physiol. 1982 Oct;70(4):1149–1155. doi: 10.1104/pp.70.4.1149. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Neuhaus G., Bowler C., Kern R., Chua N. H. Calcium/calmodulin-dependent and -independent phytochrome signal transduction pathways. Cell. 1993 Jun 4;73(5):937–952. doi: 10.1016/0092-8674(93)90272-r. [DOI] [PubMed] [Google Scholar]
- Nudel U., Zakut R., Shani M., Neuman S., Levy Z., Yaffe D. The nucleotide sequence of the rat cytoplasmic beta-actin gene. Nucleic Acids Res. 1983 Mar 25;11(6):1759–1771. doi: 10.1093/nar/11.6.1759. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Rundle S. J., Nasrallah J. B. Molecular characterization of type 1 serine/threonine phosphatases from Brassica oleracea. Plant Mol Biol. 1992 Nov;20(3):367–375. doi: 10.1007/BF00040596. [DOI] [PubMed] [Google Scholar]
- Russell D. A., Wong D. M., Sachs M. M. The anaerobic response of soybean. Plant Physiol. 1990 Feb;92(2):401–407. doi: 10.1104/pp.92.2.401. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Seo H. S., Kim H. Y., Jeong J. Y., Lee S. Y., Cho M. J., Bahk J. D. Molecular cloning and characterization of RGA1 encoding a G protein alpha subunit from rice (Oryza sativa L. IR-36). Plant Mol Biol. 1995 Mar;27(6):1119–1131. doi: 10.1007/BF00020885. [DOI] [PubMed] [Google Scholar]
- Stone J. M., Collinge M. A., Smith R. D., Horn M. A., Walker J. C. Interaction of a protein phosphatase with an Arabidopsis serine-threonine receptor kinase. Science. 1994 Nov 4;266(5186):793–795. doi: 10.1126/science.7973632. [DOI] [PubMed] [Google Scholar]
- Subbaiah C. C., Bush D. S., Sachs M. M. Elevation of cytosolic calcium precedes anoxic gene expression in maize suspension-cultured cells. Plant Cell. 1994 Dec;6(12):1747–1762. doi: 10.1105/tpc.6.12.1747. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Sukumar M., Higashijima T. G protein-bound conformation of mastoparan-X, a receptor-mimetic peptide. J Biol Chem. 1992 Oct 25;267(30):21421–21424. [PubMed] [Google Scholar]
- Tamaoki T. Use and specificity of staurosporine, UCN-01, and calphostin C as protein kinase inhibitors. Methods Enzymol. 1991;201:340–347. doi: 10.1016/0076-6879(91)01030-6. [DOI] [PubMed] [Google Scholar]
- Taylor E. R., Nie X. Z., MacGregor A. W., Hill R. D. A cereal haemoglobin gene is expressed in seed and root tissues under anaerobic conditions. Plant Mol Biol. 1994 Mar;24(6):853–862. doi: 10.1007/BF00014440. [DOI] [PubMed] [Google Scholar]
- Wang M., Sedee N. J., Heidekamp F., Snaar-Jagalska B. E. Detection of GTP-binding proteins in barley aleurone protoplasts. FEBS Lett. 1993 Aug 30;329(3):245–248. doi: 10.1016/0014-5793(93)80230-r. [DOI] [PubMed] [Google Scholar]
- Wang M., Van Duijn B., Schram A. W. Abscisic acid induces a cytosolic calcium decrease in barley aleurone protoplasts. FEBS Lett. 1991 Jan 14;278(1):69–74. doi: 10.1016/0014-5793(91)80086-i. [DOI] [PubMed] [Google Scholar]
- Ward J. M., Schroeder J. I. Calcium-Activated K+ Channels and Calcium-Induced Calcium Release by Slow Vacuolar Ion Channels in Guard Cell Vacuoles Implicated in the Control of Stomatal Closure. Plant Cell. 1994 May;6(5):669–683. doi: 10.1105/tpc.6.5.669. [DOI] [PMC free article] [PubMed] [Google Scholar]