Role of Calcium/Calmodulin in Plant Stress Response and Signaling

Calcium is a common intracellular second messenger in all the eukaryotes, regulating plethora of cellular processes. Many effects of calcium are mediated by calmodulin superfamily of calcium-binding regulatory protein. Calmodulin is a ubiquitously found and highly conserved calcium sensor throughout eukaryotes; it plays a critical role in calcium-mediated signaling involved in a myriad of cellular processes and responses. Calmodulin works by binding to short peptide sequences in target proteins, bringing about structural changes, which alter the activity of target proteins in response to changes in intracellular calcium level. Plants have evolved a complex network of calmodulin and calmodulin-binding target proteins that serve to play an important role in mediating stress-signaling pathways. Many of the calmodulin-binding proteins include transcription factors, ion channels, and metabolic enzymes that assist plant to effectively cope with environmental stress and pathogens. Extensive research over the past decade has been focused on understanding the function of calmodulin in biotic and abiotic stress response. Several studies employing genetic, molecular biology and biochemical techniques have yielded interesting insights into the function of calmodulin in modulating its various targets to provide stress resistance. In this chapter, we attempt to summarize the major findings about the regulatory role of CaM and its target proteins in abiotic and biotic stress response.