Caesium accumulation in yeast and plants is selectively repressed by loss of the SNARE Sec22p/SEC22

Abstract

The non-essential cation caesium (Cs þ ) is assimilated by all organisms. Thus, anthropogenically released radiocaesium is of concern to agriculture. Cs þ accumulates owing to its chemical similarity to the potassium ion (K þ ). The apparent lack of a Cs þ -specific uptake mechanism has obstructed attempts to manipulate Cs þ accumulation without causing pleiotropic effects. Here we show that the SNARE protein Sec22p/SEC22 specifically impacts Cs þ accumulation in yeast and in plants. Loss of Saccharomyces cerevisiae Sec22p does not affect K þ homeostasis, yet halves Cs þ concentration compared with the wild type. Mathematical modelling of the uptake time course predicts a compromised vacuolar Cs þ deposition in sec22D. Biochemical fractionation confirms this and indicates a new feature of Sec22p in enhancing non-selective cation deposition. A developmentally controlled loss-of-function mutant of the orthologous Arabidopsis thaliana SEC22 phenocopies the reduced Cs þ uptake without affecting plant growth. This finding provides a new strategy to reduce radiocaesium entry into the food chain.

Vacuolar compartmentalization as indispensable component of heavy metal detoxification in plants

“…This effect was linked to a compromised vacuolar deposition. A similar effect was observed in a loss-of-function mutant of A. thaliana orthologue SEC22 (Draxl et al 2013).…”

Cesium Toxicity Alters MicroRNA Processing and AGO1 Expressions in Arabidopsis thaliana

“…Furthermore, Adams et al (2013) reported that cesium inhibits the growth of plants via the jasmonate (JA; a lipid-based hormone) signal pathway, which regulates a wide range of processes in plants [ 12 ]. Dräxl et al (2013) showed how internal accumulation of cesium can be suppressed in plants via a mutation in a type of SNARE (Sec22p/SEC22) protein that plays a primary role in vesicle fusion [ 13 ]. By applying suppression-subtractive hybridization (SSH) and RT—PCR methods, some Cs-stress responsive genes were identified and analyzed [ 14 ].…”

Selective chemical binding enhances cesium tolerance in plants through inhibition of cesium uptake

“…Growth retardation caused by high concentrations of Cs + has been shown to be, at least partly, mediated through the jasmonate pathway, a phytohormone pathway which is mainly involved in biotic and abiotic stress responses9. Recent studies have also suggested that Cs + is sequestrated in vacuoles and a SNARE protein SEC22 may be responsible for Cs + deposition in vacuoles1011.…”