Characterization of a Ca2+-Dependent Protein Kinase from Rice Root: Differential Response to Cold and Regulation by Abscisic Acid.

Abstract

Plants can respond to a variety of biotic and abiotic signals or factors that affect their growth and development. Although the responses to these signals and factors in plants have been extensively studied at physiological and biochemical levels, the perception and intracellular transmission mechanisms remain largely unknown. Under natural growth conditions, plants do encounter various stress conditions such as drought, salinity, and high or low temperature, which have profound effects on their growth and development. Rice seedlings can respond to cold treatment with major changes in gene expression.1) It is generally recognized that patterns of protein synthesis and mRNA level change when plants are exposed to cold.2) Various stress conditions have been shown to influence protein phosphorylation. 3,4) During the early stages of cold acclimation, phosphorylation of cellular proteins and activation of protein kinases have been detected. 5)In our earlier study, the 60 kDa protein was independently phosphorylated in cold-tolerant Japonica varieties in cold treatment, but this phosphorylation is induced in cold-sensitive Indica varieties. 6) Recently, it has been reported that rice seedlings respond to cold stress of 5°C by definite changes in protein phosphorylation. 7) This suggests that subjecting rice seedlings to low temperatures results in a variety of biochemical changes at the cellular level.Low temperature treatment has been shown to induce an increase in cytosolic Ca 2ϩ levels, 8,9) and Ca 2ϩ could play an essential role in the cold-acclimation process.10,11) Ca 2ϩ plays important roles in numerous physiological processes and the presence of Ca 2ϩ -regulated protein kinases will have wider implications in cellular signal transduction.12,13) Ca 2ϩ -dependent protein kinases (CDPKs) play a key role in stress and Ca 2ϩ -mediated signal transduction. As a specific group of kinases CDPKs require only micromolar concentrations of Ca 2ϩ for their activity, do not require calmodulin or phospholipids in plants and have been identified as Ca 2ϩ -dependent and calmodulin-independent serine/threonine kinases.14,15)The plant CDPKs have been shown to phosphorylate a number of exogenous substrates, including histone III-S. 16)CDPKs exist as multiple isoforms 17) and isolation of cDNA further revealed that these enzymes are encoded by a multigene family. 18,19) As for their localization, CDPKs are either membrane-associated 20,21) or cytosolic in nature. 22,23) A 32 kDa CDPK was detected during regeneration of rice cultured suspension cells by an in-gel kinase assay.24) Also a 45 kDa Ca 2ϩ -and phospholipid-dependent protein kinases in rice embryos and leaves were identified in previous studies.25) A 45 kDa CDPK, which can phosphorylate histone III-S in gel, was found in rice leaf under darkness in the presence of Ca 2ϩ and phosphatidylserine 26) ; their functions, however, remain to be clarified. Rice seedlings under cold stress induce a 47 kDa CDPK in an increasing manner in leaf sheath tissues. 27) However, the functi...

Autophosphorylation and Subcellular Localization Dynamics of a Salt- and Water Deficit-Induced Calcium-Dependent Protein Kinase from Ice Plant

“…Many other examples of multiple stimuli inducing the expression of individual CPKs are known. Increased steady-state transcripts, abundance, or activities of various CPKs in response to low-temperature, ionic, osmotic, water deficit, wounding, and elicitor treatments implicate their possible involvement in signaling response networks for these environmental stimuli (Botella et al, 1996;Pestenácz and Erdei, 1996;Yoon et al, 1999;Komatsu et al, 2001;Murillo et al, 2001;Romeis et al, 2001;Chico et al, 2002;Llop-Tous et al, 2002). The remaining challenge is to determine the specific contribution to signaling pathways made by each individual CDPK and the degree of overlap or redundancy among these different signaling cascades.…”

“…Pharmacological studies have implicated CDPK participation in fungal pathogen defense (Romeis et al, 2000), wound signaling (Schaller and Oecking, 1999), and osmotic stress signaling (Pestenácz and Erdei, 1996;Taybi and Cushman, 1999). Furthermore, the expression patterns or activity changes of some CDPKs have suggested functional roles in low-temperature, ionic, osmotic, or water deficit stress signaling (Urao et al, 1994;Botella et al, 1996;Pestenácz and Erdei, 1996;Yoon et al, 1999;Komatsu et al, 2001;Chico et al, 2002;Llop-Tous et al, 2002), light responses (Pagnussat et al 2002), jasmonate signaling , and elicitor-induced signaling (Yoon et al, 1999;Murillo et al, 2001;Romeis et al, 2001).…”

OsCDPK13, a calcium-dependent protein kinase gene from rice, is induced by cold and gibberellin in rice leaf sheath

“…Drought, salt, cold, light, and hormones can influence the expression or activity of various CDPKs in plants (Sopory and Munshi, 1998). Increased CDPK activity and Ca 2+ -dependent protein phosphorylation were observed in rice seedlings exposed to cold (Li and Komatsu, 2000;Komatsu et al, 2001) and hormone treatment (Kawasaki et al, 1993;Karibe and Komatsu, 1997;Yang and Komatsu, 2000). Using sense and antisense transgenic rice, CDPKs were identified as signaling components downstream of both the gibberellin (GA)-binding protein and the brassinosteroid receptor (Sharma et al, 2001;Sharma and Komatsu, 2002).…”

Structure and functions of plant calcium-dependent protein kinases.

“…A different regulation by plant hormones was observed in rice roots, where the activity of a 45 kDa CDPK decreased previously by cold was recovered by exogenous abscisic acid (ABA). This may suggest that the 45 kDa protein kinase activity regulated by ABA is involved in the cold-stress response in rice (Komatsu et al, 2001). Studies of ACPK1 from the mesocarp of grape barriers (Vitis vinifera x V. labrusca) revealed that ABA stimulates both the activity of the kinase and mRNA level, but not at the same time.…”