Connecting vacuolar and plasma membrane transport networks

Abstract

The coordinated control of ion transport across the two major membranes of differentiated plant cells, the plasma and the vacuolar membranes, is fundamental in cell physiology. The stomata responses to the fluctuating environmental conditions are an illustrative example. Indeed, they rely on the coordination of ion fluxes between the different cell compartments. The cytosolic environment, which is an interface between intracellular compartments, and the activity of the ion transporters localised in the different membranes influence one each other. Here we analyse the molecular mechanisms connecting and modulating the transport processes at both the plasma and the vacuolar membranes of guard cells.

The viscoelastic properties ofNicotiana tabacumBY-2 suspension cell lines adapted to high osmolarity

“…Vacuoles constitute a key component in plants cell osmoregulation, their content and mechanical properties are important for the stress response (Afzal et al, 2016; Maurel et al, 1997). How it could work a coordination between ions and water transport through PM and tonoplast, it has been proposed for guard cells (Cubero-Font & De Angeli, 2021). By BLS we obtained data on approximate vacuoles areas, that were distinguished from cytoplasmic bands areas pushed to cell walls by vacuole’s pressure.…”

Plant Proton Pumps and Cytosolic pH-Homeostasis

“…Coordination can be achieved by ionic conditions in the cytosol, in particular calcium ions and nitrate, cytosolic pH, nucleotides, malate, kinases, and phosphatases, redox conditions, and membrane potential. Assuming lack of coordination of transport processes at tonoplast and plasma membrane, the cytosolic solute concentration would putatively increase by 150 mM/min in guard cells during stomata opening ( Cubero-Font and de Angeli, 2020 ).…”

“…Kinases might act on proteins in different membranes, such as the receptor-like kinase KIN7, which locates to the tonoplast and the plasma membrane ( Isner et al, 2018 ; van Kleeff et al, 2018 ; Subba et al, 2020 ) or the SOS2/SOS3 complex, which activates cation-proton-antiporters (NHX, CAX), V-ATPase, and PPase ( Shabala et al, 2020 ). Other candidates are MAPKs, which might act on transporters, too ( Cubero-Font and de Angeli, 2020 ). Together with membrane-associated phosphatases they seem to be key players of transport regulation: PP2A dephosphorylates CLC-a ( Subba et al, 2020 ), PP2A-C5 interacts with the vacuolar CLCs -a, -b, -c, and –g ( Hu et al, 2017 ).…”

K+ and pH homeostasis in plant cells is controlled by a synchronized K+/H+ antiport at the plasma and vacuolar membrane

“…Stomatal movement depends on the transport of K + -salts across two membrane systems connected in series, the PM, and the tonoplast (Hedrich, 2012;Sierla et al, 2016;Eisenach & De Angeli, 2017;Jezek & Blatt, 2017;Martinoia, 2018;Cubero-Font & De Angeli, 2021). The vacuole usually occupies > 90% of the cell volume, with the VM separated from the PM by only a small cytoplasmic volume.…”

“…For this reason, changes in membrane transport at one of the two membranes inevitably affect the electrochemical transport processes at the other membrane (Horaruang et al, 2020;Dreyer et al, 2023). Due to the difficulty of accessing the tonoplast in vivo, studies of the coupling of PM and VM are rare (Cubero-Font & De Angeli, 2021) and our knowledge on how the bulk transport of K + -and anion-salts across both membranes is coupled and what role Ca 2+ and pH changes play is still fragmental.…”