Abstract
This work critically discusses the direct and indirect effects of natural polyamines and their catabolites such as reactive oxygen species and γ-aminobutyric acid on the activity of key plant ion-transporting proteins such as plasma membrane H+ and Ca2+ ATPases and K+-selective and cation channels in the plasma membrane and tonoplast, in the context of their involvement in stress responses. Docking analysis predicts a distinct binding for putrescine and longer polyamines within the pore of the vacuolar TPC1/SV channel, one of the key determinants of the cell ionic homeostasis and signaling under stress conditions, and an additional site for spermine, which overlaps with the cytosolic regulatory Ca2+-binding site. Several unresolved problems are summarized, including the correct estimates of the subcellular levels of polyamines and their catabolites, their unexplored effects on nucleotide-gated and glutamate receptor channels of cell membranes and Ca2+-permeable and K+-selective channels in the membranes of plant mitochondria and chloroplasts, and pleiotropic mechanisms of polyamines’ action on H+ and Ca2+ pumps.
Highlights
Polyamines (PAs) are plant growth regulators and important components of plant stress responses (Alcázar et al, 2010; Takahashi and Kakehi, 2010; Pottosin and Shabala, 2014; Pál et al, 2015; Paschalidis et al, 2019)
Polyamines induce a rapid depolarization in roots and leaves (Fromm et al, 1997; Ozawa et al, 2010; Pottosin et al, 2014a)
PM Put transporter, PUT3, is phosphorylated by SOS2 (CIPK24). It forms a tertiary complex with SOS1 (PM Na+/H+ antiporter) and SOS2, key elements in response to salinity; within this complex, the activity of PUT3 and SOS1 is synergistically modulated (Chai et al, 2020)
Summary
Polyamines (PAs) are plant growth regulators and important components of plant stress responses (Alcázar et al, 2010; Takahashi and Kakehi, 2010; Pottosin and Shabala, 2014; Pál et al, 2015; Paschalidis et al, 2019). PAs were not originally designed as signaling compounds but acquired this function during evolution by leveraging on a strong variation of levels of individual PAs and their catabolites during plant responses to changing environment. Owing to this level of complexity, the initial. Polyamines Action on Ion Transport in Stress question should be related to the primary effects of different PAs and their catabolites (e.g., ROS) on individual ion transporters. Are these effects direct and specific for different PAs? The aim of this work is to elucidate diverse effects of PAs on key plant membrane ion transporters to stimulate more focused studies in this field
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