High External K+ Concentrations Impair Pi Nutrition, Induce the Phosphate Starvation Response, and Reduce Arsenic Toxicity in Arabidopsis Plants

Potassium (K+) and phosphorous (Pi) are two of the most important nutrients required by plants and there is an interest in studying how they are acquired. Most studies have focused on the characterization of the mechanisms involved in K+ and Pi uptake and their distribution within the plants, as well as the regulatory mechanisms involved. Evidence is emerging which points to interactions in the nutrition of different nutrients and to the existence of crosstalk in the signaling cascades regulating their acquisition. However, the interaction between K+ and Pi has been scarcely studied. Here we show that high concentrations of K+ in the external solution inhibit Pi uptake and impair Pi nutrition in Arabidopsis plants, resulting in the induction of phosphate starvation response (PSR) and the upregulation of genes encoding root phosphate uptake systems. The high K+-induced PSR depends on the PHR1 and PHL1 transcription factors that are key pieces of Pi signaling in Arabidopsis. Importantly, high K+ reduces arsenic accumulation in plants and its toxic effects. The results presented may help to design strategies to reduce Pi deficiency as well as the accumulation of arsenic in crops.This work was supported by grant AGL2015-66434-R and grant BIO2016-81957-REDT from Ministerio de Economía y Competitividad, Spain, and grant 20806/PI/18 from Fundación Séneca de la Región de Murcia, Spain. R.R. is recipient of a FPU fellowship from Ministerio de Educación y Ciencia, Spain (FPU13/03184)We acknowledge support by the CSIC Open Access Publication Initiative through its Unit of Information Resources for Research (URICI)Peer reviewe