Calcium and Signal Transduction in Plants

Abstract

Environmental and hormonal signals control diverse physiological processes in plants. The mechanisms by which plant cells perceive and transduce these signals are poorly understood. Understanding biochemical and molecular events involved in signal transduction pathways has become one of the most active areas of plant research. Research during the last 15 years has established that Ca2+ acts as a messenger in transducing external signals. The evidence in support of Ca2+ as a messenger is unequivocal and fulfills all the requirements of a messenger. The role of Ca2+ becomes even more important because it is the only messenger known so far in plants. Since our last review on the Ca2+ messenger system in 1987, there has been tremendous progress in elucidating various aspects of Ca(2+) -signaling pathways in plants. These include demonstration of signal-induced changes in cytosolic Ca2+, calmodulin and calmodulin-like proteins, identification of different Ca2+ channels, characterization of Ca(2+) -dependent protein kinases (CDPKs) both at the biochemical and molecular levels, evidence for the presence of calmodulin-dependent protein kinases, and increased evidence in support of the role of inositol phospholipids in the Ca(2+) -signaling system. Despite the progress in Ca2+ research in plants, it is still in its infancy and much more needs to be done to understand the precise mechanisms by which Ca2+ regulates a wide variety of physiological processes. The purpose of this review is to summarize some of these recent developments in Ca2+ research as it relates to signal transduction in plants.

Interaction of Arabidopsis kinesin‐like calmodulin‐binding protein with tubulin subunits: modulation by Ca2+‐calmodulin

“…Calmodulin, a ubiquitous and multifunctional Ca2+-binding protein in eukaryotes, interacts and modulates the activity/function of a number of proteins (Poovaiah and Reddy, 1993;Roberts and Harmon, 1992). Here, we show that the truncated KCBP containing the motor domain along with the calmodulin-binding region does not bind to tubulin subunits in the presence of Ca2+-calmodulin.…”

“…Among motor proteins, the heavy chain of some actin-based myosin motors and light chain of microtubule-based kinesin motors show calcium and calmodulin-dependent regulation (Matthies etal., 1993;Wolenski, 1995). The presence of a calmodulin-binding domain next to the motor domain in KCBP and its binding to calmodulin at micromolar calcium concentration raises an interesting possibility that calcium, an important messenger molecule in plant and animal systems (Gilroy and Trewavas, 1994;Poovaiah and Reddy, 1993;Roberts and Harmon, 1992), through calmodulin, may regulate the interaction of KCBP with tubulin. In the present study we have investigated the binding of KCBP to tubulin subunits and the possible role of Ca2+-calmodulin in modulating KCBP interaction with tubulin subunits.…”

La résistance induite : une nouvelle stratégie de défense des plantes contre les agents pathogènes

“…L'augmentation de la concentration intracellulaire de Ca 2+ joue un rôle fondamental dans plusieurs mécanismes incluant: 1) l'activation de la G-1,3-glucane synthase, l'enzyme impliquée dans la formation de callose, un polymère structural de të-1,3-glucanes (Kauss et al 1989); 2) la stimulation des protéines kinases impliquées dans la phosphorylation des protéines; 3) la formation du complexe Ca 2+ -calmoduline associé au cytosquelette; et 4) la transduction du signal au noyau (Poovaiah et Reddy 1993;fig. 5).…”

Gibberellins: regulating genes and germination

“…(e) Autoradiograph showing Ca# + -activated phosphorylation of histone (used as a model substrate) by a CDPK extracted from nonhormone treated aleurone tissue assayed as in (c) Ca# + and calmodulin. Changes in the concentrations of cytoplasmic Ca# + , often mediated through the regulatory protein CaM, are recognized as ubiquitous signal transduction elements in animal and plant cells (reviewed in Gilroy, Bethke & Jones, 1993 ;Poovaiah & Reddy, 1993 ;Bush, 1995). The cytoplasmic Ca# + concentration ([Ca# + ]) of barley and wheat aleurone cells is elevated from 100 n to around 500 n by GA, whereas ABA reduces Ca# + concentrations ( Fig.…”