The chloroplast located HKT transporter plays an important role in sporophyte development in Physcomitrium patens

Cell survival depends on the maintenance of cell homeostasis that involves all the biochemical, genomic and transport processes that take place in all the organelles within an eukaryote cell. In particular, ion homeostasis is required to regulate the membrane potential and solute transport across all membranes, any alteration in these parameters will reflect in the malfunctioning of any organelle. In plant cells, sodium transporters play a central role in keeping the concentrations of this cation across all membranes under physiological conditions to prevent its toxic effects. HKT transporters are a family of membrane proteins exclusively present in plants, with some homologs being present in prokaryotes. HKT transporters have been associated to salt tolerance in plants, retrieving any leak of the cation into the xylem, or removing it from aerial parts to be transported to the roots along the phloem. This function has been assigned as most of the HKT transporters are located at the plasma membrane. Here, we report the localization of the moss HKT from Physcomitrium patens to the thylakoid membrane, and its mutation that leads to several alterations in the phenotype of the organism, together with the changes in expression of close to 1000 genes. Down regulation of photosynthesis related genes and the upregulation of glycolysis/respiration and ion transport genes help to explain the observed phenotype.