Involvement of calmodulin and calmodulin-like proteins in plant responses to abiotic stresses

Abstract

Transient changes in intracellular Ca2+ concentration have been well recognized to act as cell signals coupling various environmental stimuli to appropriate physiological responses with accuracy and specificity in plants. Calmodulin (CaM) and calmodulin-like proteins (CMLs) are major Ca2+ sensors, playing critical roles in interpreting encrypted Ca2+ signals. Ca2+-loaded CaM/CMLs interact and regulate a broad spectrum of target proteins such as channels/pumps/antiporters for various ions, transcription factors, protein kinases, protein phosphatases, metabolic enzymes, and proteins with unknown biochemical functions. Many of the target proteins of CaM/CMLs directly or indirectly regulate plant responses to environmental stresses. Basic information about stimulus-induced Ca2+ signal and overview of Ca2+ signal perception and transduction are briefly discussed in the beginning of this review. How CaM/CMLs are involved in regulating plant responses to abiotic stresses are emphasized in this review. Exciting progress has been made in the past several years, such as the elucidation of Ca2+/CaM-mediated regulation of AtSR1/CAMTA3 and plant responses to chilling and freezing stresses, Ca2+/CaM-mediated regulation of CAT3, MAPK8 and MKP1 in homeostasis control of reactive oxygen species signals, discovery of CaM7 as a DNA-binding transcription factor regulating plant response to light signals. However, many key questions in Ca2+/CaM-mediated signaling warrant further investigation. Ca2+/CaM-mediated regulation of most of the known target proteins is presumed based on their interaction. The downstream targets of CMLs are mostly unknown, and how specificity of Ca2+ signaling could be realized through the actions of CaM/CMLs and their target proteins is largely unknown. Future breakthroughs in Ca2+/CaM-mediated signaling will not only improve our understanding of how plants respond to environmental stresses, but also provide the knowledge base to improve stress-tolerance of crops.

Copper-induced overexpression of genes encoding antioxidant system enzymes and metallothioneins involve the activation of CaMs, CDPKs and MEK1/2 in the marine alga Ulva compressa

“…Moreover, it was determined that there is a cross-talk among increases in calcium and hydrogen peroxide since the increase in calcium levels induces an increase in hydrogen peroxide levels, and vice versa (González et al 2012a). Moreover, it is well known that CaMs and CDPKs are activated in response to intracellular calcium increases in plants (Cheng et al 2002;Zeng et al 2015), and that the MEK1/2 pathway is activated by an increase in hydrogen peroxide level (Jonak et al 2004), all of which have been observed to be cross-talking events (Wurzinger et al 2011;Yeh et al 2007). Considering that calcium and hydrogen peroxide induction are crosstalking processes in U. compressa, it is not surprising that the increase in the level of transcripts encoding enzymes of the antioxidant system and MTs is completely, or partially, inhibited by CaMs and CDPKs inhibitors, as well as by a MEK1/2 inhibitor.…”

“…In plants, the increase in expression of genes encoding antioxidant enzymes and enzymes involved in ASC and GSH synthesis requires calcium-dependent signaling proteins such as calmodulins (CaMs) Zeng et al 2015), calcium-dependent protein kinases (CDPKs) (Ding et al 2012;Schulz et al 2013) and Mytogen Activated Protein Kinases (MAPKs) such as the MAPKK MEK1/2 and the MAPK p38 (Jiang and Song 2008;Shan et al 2011;Yeh et al 2007;Zhang et al 2007). In addition, it has been shown that there is a cross-talk among CaMs, CDPKs and MEK1/2 signaling proteins (Wurzinger et al 2011;Yeh et al 2007).…”

Phosphatidylinositol‐hydrolyzing phospholipase C4 modulates rice response to salt and drought

“…In animal cells, IP 3 binds to its receptor, triggering the opening of the Ca 2+ channel and releases Ca 2+ from the endoplasmic reticulum into the cytoplasm. Ca 2+ ‐mediated signalling plays important roles in plant response to osmotic stress (Zeng et al, ). However, evidence for a direct role of IP 3 in cytoplasmic Ca 2+ increase remains scarce in plants.…”

Molecular mechanisms involved in postharvest chilling tolerance of pomegranate fruit

“…Regarding transcripts involved in MAPK and Ca 2+ signaling pathways: we identified three MAPKKKs and three calmodulin‐like protein (CML) transcripts that were commonly up‐regulated in the relatively chilling‐tolerant fruits in all three model systems. The involvement of these proteins in plant responses to abiotic stresses is well documented . Calcium acts as a second messenger, whose cytosolic levels increase in response to abiotic stress, and its signal is perceived by Ca 2+ sensors, such as CDPKs and CMLs, which participate in transferring the signal downstream to activate the MAPK signaling cascade, which induces the expression of CBF/DREB and other transcription factors, and thereby imparts cold tolerance …”