Choline but not its derivative betaine blocks slow vacuolar channels in the halophyte Chenopodium quinoa: Implications for salinity stress responses

Abstract

a b s t r a c tActivity of tonoplast slow vacuolar (SV, or TPC1) channels has to be under a tight control, to avoid undesirable leak of cations stored in the vacuole. This is particularly important for salt-grown plants, to ensure efficient vacuolar Na + sequestration. In this study we show that choline, a cationic precursor of glycine betaine, efficiently blocks SV channels in leaf and root vacuoles of the two chenopods, Chenopodium quinoa (halophyte) and Beta vulgaris (glycophyte). At the same time, betaine and proline, two major cytosolic organic osmolytes, have no significant effect on SV channel activity. Physiological implications of these findings are discussed.

Epidermal bladder cells confer salinity stress tolerance in the halophyte quinoa and Atriplex species

“…Indeed, it was shown earlier that some of so‐called ‘compatible solutes’ could possess a strong ability to block ion channels mediating plant ionic homeostasis (e.g. the role of choline in vacuolar Na + sequestration, which originates from its ability to block slow vacuolar channels; Pottosin et al , or improved K + retention in plant tissues treated with exogenous glycine betaine; Cuin and Shabala ). In addition, some compatible solutes also act as scavengers of reactive oxygen species (ROS; Peshev et al .…”

“…Indeed, it was shown earlier that some of so-called 'compatible solutes' could possess a strong ability to block ion channels mediating plant ionic homeostasis (e.g. the role of choline in vacuolar Na + sequestration, which originates from its ability to block slow vacuolar channels; Pottosin et al 2014, or improved K + retention in plant tissues treated with exogenous glycine betaine; Cuin and Shabala 2005). In addition, some compatible solutes also act as scavengers of reactive oxygen species (ROS; Peshev et al 2013;Smirnoff and Cumbes 1989), so if accumulated in high concentrations, may potentially prevent ROS-induced changes in the activation of a broad range of Na + , K + and Ca 2+ permeable ion channels (see Demidchik and Maathuis 2007 for a review).…”

Revealing mechanisms of salinity tissue tolerance in succulent halophytes: A case study for Carpobrotus rossi

“…Thus, changes in vacuolar [K + ] act as an efficient tool for a negative feedback control of SV activity, assisting Na + retention in vacuoles. Another possible candidate for the blockage of SV channels is choline (Pottosin, Bonales‐Alatorre, & Shabala, ).…”

“…Another possible candidate for the blockage of SV channels is choline (Pottosin, Bonales-Alatorre, & Shabala, 2014).…”

Energy costs of salinity tolerance in crop plants

“…Thus, Na + efflux across the PM of root cortical cells could be one of the most energy consuming steps in whole plant Na + transport, and is the most important as roots must exclude 98% of the Na + in the soil solution (Munns, ). Leaks back from the vacuole to the cytoplasm via the fast and slow vacuolar channels would also need to be under tight control to prevent futile cycling with consequent energy inefficiency (Bonales‐Alatorre et al ., ; Pottosin et al ., ). We need to be very confident that the measurements of high Na + influx into roots are correct, and represent, at least in large part, the trans‐PM Na + influx.…”