Phosphorus alleviates arsenic toxicity in barley by modulating phosphate transporter gene expression and reducing...

Arsenic (As) contamination poses a major threat to global crop production and food safety. Although phosphorus (P) supplementation can alleviate As toxicity by inhibiting its uptake, the molecular mechanisms underlying this interaction remain poorly understood. In this study, we examined P-As interactions in two barley genotypes with contrasting As tolerance: the As-tolerant BCS158 and the As-sensitive BCS16. Plants were hydroponically grown under varying As (0, 10, and 100 μM) and P (0, 50, and 500 μM) concentrations. High As exposure (100 μM) significantly reduced plant biomass, decreasing root and shoot dry weights by 34.5% and 38.5% in BCS158, and by 36.9% and 45.4% in BCS16, respectively. Arsenic stress also impaired photosynthesis and induced oxidative stress, as indicated by elevated levels of superoxide radical (O₂^•-) and malondialdehyde (MDA) in both roots and shoots. The As-sensitive genotype BCS16 had significantly higher As concentrations in roots and shoots compared to BCS158, which explains its greater physiological sensitivity. Notably, P supplementation effectively alleviated As toxicity by lowering tissue As concentrations. This was accompanied by the down-regulation of key transporter genes involved in As and P/As transport, including HvLsi1, HvLsi2, HvPHO1.2, and HvPHO2. Together, these findings demonstrate that elevated P levels suppress the expression of As-related transporter genes, thereby reducing As accumulation and alleviating its toxic effects in barley.