Modulation of Ion Transport Across Plant Membranes by Polyamines: Understanding Specific Modes of Action Under Stress
Igor Pottosin, Miguel Olivas-Aguirre, Oxana Dobrovinskaya, Isaac Zepeda‐Jazo, Sergey Shabala
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 Ca 2+ 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 Ca 2+ -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 Ca 2+ -permeable and K + -selective channels in the membranes of plant mitochondria and chloroplasts, and pleiotropic mechanisms of polyamines’ action on H + and Ca 2+ pumps.