Humic Acid Confers Oxidative Stress Tolerance by Enhancing the Transcription of Redox Genes in Arabidopsis and Oilseed Rape

Abstract

Humic acid (HA), a major component of humic substances in soils, is recognized for its role in enhancing plant growth, nutrient uptake, and abiotic stress tolerance. However, the molecular mechanisms underlying HA-mediated oxidative stress tolerance remain unclear. In this study, we investigate the role of HA in enhancing oxidative stress resilience in Arabidopsis thaliana and Brassica napus. Transcriptome analysis and gene ontology enrichment revealed that HA treatment significantly up-regulates genes associated with oxidative stress responses and cellular homeostasis. Quantitative RT-PCR confirmed the induction of key redox-related genes, including OXS3, SEN1, and ROXY family members. Physiological assays demonstrated that HA mitigates methyl viologen (MV)-induced oxidative stress damage, as evidenced by improved chlorophyll contents and reduced malondialdehyde (MDA) and hydrogen peroxide (H2O2) accumulation. Notably, HA treatment also alleviated oxidative stress symptoms and reduced MDA levels in B. napus seedlings exposed to MV, supporting HA’s protective role beyond model species. These findings suggest that HA primes redox-responsive gene expression and mitigates ROS-induced damage, offering a promising strategy for improving crop resilience under climate-induced abiotic stress conditions. © The Author(s), under exclusive licence to Korean Society of Plant Biologist 2025.