Metallochaperone Protein OsHIPP36 Is Involved in Arsenic(III) Tolerance and Translocation in Rice ( Oryza sativa L.)

BACKGROUND AND AIMS: Arsenic (As) contamination in agricultural soils threatens crop production and food safety due to its toxicity. Heavy metal-associated isoprenylated plant proteins (HIPPs) act as metallochaperone involved in metal ion homeostasis. Here, we show that the previously uncharacterized OsHIPP36 affects As(III) tolerance and translocation in rice. METHODS: The expression pattern of OsHIPP36 was examined using RT-qPCR and GUS staining. Subcellular localization of OsHIPP36 was examined by transiently expressing an OsHIPP36-GFP fusion in rice protoplasts and tobacco leaves, while its functional role was assessed through heterologous expression in the As-sensitive yeast mutant Δycf1. The mutant and overexpressing transgenic lines were generated using CRISPR/Cas9 technology. As(III) levels were measured by ICP-MS and protein interactions tested using LCI, BiFC and Co-IP assays. KEY RESULTS: The OsHIPP36 protein is targeted to the plasma membrane, and its expression is significantly induced by As(III) stress. In yeast assays, expression of OsHIPP36 in the Δycf1 mutant inhibited yeast growth and led to higher intracellular As(III) accumulation. In rice, the loss of OsHIPP36 enhanced tolerance to As(III), leading to an increased As(III) retention in the roots and decreased transport to shoots. CONCLUSION: OsHIPP36 is a plasma membrane-localized metallochaperone induced by As(III) stress and plays a negative role in rice As(III) tolerance. To our knowledge, this study provides the first evidence that HIPP proteins influence As(III) tolerance and accumulation in rice.