Physiological and proteomic analyses reveal cAMP‐regulated key factors in maize root tolerance to heat stress

Abstract

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cAMP Is a Promising Regulatory Molecule for Plant Adaptation to Heat Stress

“…Plants promote resilience by altering their cellular homeostasis and morphology under heat stress. Molecular processes underlying these responses have been intensively studied and found to encompass diverse mechanisms operating across a broad range of cellular components [ 7 , 9 , 23 , 24 ]. The accumulating experimental evidence suggests that cAMP regulates thermotolerance in plants, despite the fact that the identification of cAMP target proteins remains far behind that in animals [ 3 , 6 ].…”

“…When maize was exposed to heat stress, exogenous cAMP application obviously increased the expression of CSC1-like protein (Ca 2+ transporter) and the uptake of Ca 2+ in roots [ 24 ], as well as the expression of calmodulin protein 2 in leaves [ 9 ]; In tobacco BY-2 cells overexpressing the ‘cAMP-sponge’ as a genetic tool reducing intracellular cAMP levels (named as cAS cell), and cAMP deficiency significantly changed the expression of calcium-dependent lipid-binding (CaLB domain) family protein, annexin 2, calreticulin 3, calcineurin B-like 3, calcium-dependent phosphotriesterase superfamily protein, and calcium-binding EF-hand family protein under heat stress [ 7 ]. Interestingly, when Arabidopsis was subjected to heat stress, heat-increased AMP activated cyclic nucleotide-gated channel 6 (AtCNGC6) activity and thus resulted in an influx of Ca 2+ into the cell via AtCNGC6, facilitating the expression of HSP genes and the acquisition of thermotolerance [ 25 ]; under the elevated cytosolic Ca 2+ concentration, CaM2, CaM3, CaM5, and CaM7 negatively regulated Ca 2+ conductivity of CNGC6 by binding its atypical isoleucine-glutamine motif, and thus led to a marked decrease in plasma membrane inward Ca 2+ current, suggesting that the atypical isoleucine-glutamine motif plays an important role in CaM binding and the feedback regulation of the CNGC6 channel [ 29 ].…”

“…It has been confirmed that the intracellular and extracellular content of ROS significantly increased in tobacco BY2 cells under a heat stress condition [ 7 , 36 , 37 ]. In maize leaves and roots, the application of cAMP analogous 8-Br-cAMP increased H 2 O 2 content but had no influence on RBOHB expression under no heat stress, whereas prominently reduced H 2 O 2 content but increased RBOHB expression under heat stress [ 9 , 24 ]. In tobacco cAS cells, cAMP deficiency resulted in a greater accumulation of RBOHC (A0A1S3YBQ2), which is consistent with the accumulation of intracellular ROS.…”

“…The phytohormone abscisic acid (ABA) is a growth regulator that is involved in the adaptation to heat stress response by changing the adaptation process [ 9 , 24 , 42 , 43 ]. Emerging evidence has increasingly fit cAMP in the signaling pathways of ABA-dependent plant heat stress responses.…”

“…Emerging evidence has increasingly fit cAMP in the signaling pathways of ABA-dependent plant heat stress responses. Recent studies characterized that ZmRPP13-LK3 and ZmPSiP not only had AC activity but also involved ABA-mediated resistance to heat stress in maize [ 9 , 24 ]. Heat-enhanced cAMP content was decreased in maize ABA biosynthesis-deficient mutant viviparous-5 ( vp5 ) comparable to its wild type Vp5, which is consistent with the change of heat-enhanced ZmRPP13-LK3 and ZmPSiP expression.…”