Ca2+/Calmodulin Complex Triggers CAMTA Transcriptional Machinery Under Stress in Plants: Signaling Cascade and Molecular Regulation

Abstract

Calcium (Ca2+) ion is a critical ubiquitous intracellular second messenger, acting as a lead currency for several distinct signal transduction pathways. Transient perturbations in free cytosolic Ca2+ ([Ca2+]cyt) concentrations are indispensable for the translation of signals into adaptive biological responses. The transient increase in [Ca2+]cyt levels is sensed by an array of Ca2+ sensor relay proteins such as calmodulin (CaM), eventually leading to conformational changes and activation of CaM. CaM, in a Ca2+-dependent manner, regulates several transcription factors (TFs) that are implicated in various molecular, physiological, and biochemical functions in cells. CAMTA (calmodulin-binding transcription activator) is one such member of the Ca2+-loaded CaM-dependent family of TFs. The present review focuses on Ca2+ as a second messenger, its interaction with CaM, and Ca2+/CaM-mediated CAMTA transcriptional regulation in plants. The review recapitulates the molecular and physiological functions of CAMTA in model plants and various crops, confirming its probable involvement in stress signaling pathways and overall plant development. Studying Ca2+/CaM-mediated CAMTA TF will help in answering key questions concerning signaling cascades and molecular regulation under stress conditions and plant growth, thus improving our knowledge for crop improvement.

Comprehensive genome-wide analysis of calmodulin-binding transcription activator (CAMTA) in Durio zibethinus and identification of fruit ripening-associated DzCAMTAs

“…B, C, and D). As already discussed, CAMTAs are Ca 2+ /CaM-regulated TFs that have long been linked to phytohormones, such as ABA, ethylene, and auxins [ 14 ]. Coherently, DzCAMTA3PinG and DzCAMTA8PinG were linked with positive regulation of ABA, ethylene, and auxins (Additional file 6 - Fig.…”

“…Ca 2+ is an important second messenger that mediates responses to external stimuli and hormonal fluctuations via Ca 2+ sensors, such as CaM [ 14 , 77 , 78 ]. The role of Ca 2+ is further extended in fruit ripening via the intervention of cross-wired mesh of regulatory networks [ 27 , 77 ].…”

“…Often, molecular mechanisms mediating plant responses to environmental and hormonal signals involve signaling cascades in which Ca 2+ acts as a pivotal second messenger [ 12 , 13 ]. Perturbations in cytosolic Ca 2+ levels are sensed and interpreted by an array of Ca 2+ -binding proteins that function as signal sensors [ 14 , 15 ]. Calmodulin (CaM) is a well-characterized Ca 2+ sensor, which is known to modulate target proteins such as TFs [ 16 ], including the well-known CaM-binding transcription activators (CAMTAs) [ 17 , 18 ].…”

Plant Defense Responses to Biotic Stress and Its Interplay With Fluctuating Dark/Light Conditions

“…Many Ca 2+ and Ca 2+ sensor-associated transcription factors (TFs) are implicated in stress signaling in plants ( Carrion et al, 1999 ; Singh and Virdi, 2013 ; Ranty et al, 2016 ; Chung et al, 2020 ; Shen et al, 2020 ). The largest and best characterized family of Ca 2+ /CaM-dependent TFs are CAMTAs ( Iqbal et al, 2020b ). CAMTA3 has been reported enormously as a suppressor of plant biotic defense responses ( Benn et al, 2016 ; Jacob et al, 2018 ; Kim et al, 2020 ).…”

Role of Jasmonates, Calcium, and Glutathione in Plants to Combat Abiotic Stresses Through Precise Signaling Cascade

“…The promoter region analysis of the Ca 2+ shows biased nature toward abiotic stress responsive genes. Three among four Ca 2+ regulated promoter regions were reported to be indispensable for abiotic stress responses (Iqbal et al, 2020). About 30 CDPK genes have been reported in Arabidopsis that have role in abiotic stress responses (Hrabak et al, 2003).…”