ARABIDOPSIS NITRATE REGULATED 1 negatively regulates the tolerance of salt stress by controlling ion homeostasis and GA metabolism

Previous studies have linked nitrate uptake regulation in plants to salt stress tolerance. Building on this, our study aimed to investigate the role of the ANR1 gene, involved in nitrate sensing and signaling, in salt stress response using anr1 knock-down plants. Our results showed that anr1 plants exhibited improved tolerance to salt stress compared to Col-0, with better root length, biomass, and chlorophyll content. Under salt stress, anr1 plants accumulated less reactive oxygen species (ROS) and showed smaller increment in malondialdehyde (MDA) levels relative to control conditions. They also maintained higher nitrate and anthocyanin contents and a lower Na⁺/K⁺ ratio, indicating enhanced physiological stability. Based on their superior growth under salt stress, we further explored the role of gibberellin (GA), a hormone regulating plant growth. Normally, GA signaling is suppressed under salt stress. However, anr1 plants accumulated lower levels of DELLA proteins such as GAI, and treatment with paclobutrazol (PBZ), a GA biosynthesis inhibitor, reduced the salt tolerance of anr1 plants to Col-0 levels, suggesting that a link between ANR1 and GA metabolism in stress adaptation. While ANR1's role in germination-stage stress response has been noted before, this study highlights its function during the seedling stage, particularly in modulating salt stress tolerance through in association with GA. These findings indicate that ANR1 is a promising target for gene editing to enhance crop resilience under saline conditions.