Integrated Transcriptomic and Physiological and Biochemical Analysis Revealed Response Mechanism of Rice (Oryza...

Methylmercury (MeHg), a pervasive environmental contaminant, poses significant human health risks due to its bioaccumulation in food chain, particularly through rice, a dietary staple for billions of people. Although extensive research has been conducted on the environmental cycling and health impacts of MeHg on rice, limited attention has been given to understanding the molecular and physiological responses to MeHg stress, which is crucial for elucidating the mechanisms of detoxification and adaptation. Herein, we conducted pot experiments of rice with varying MeHg concentrations of soil, followed by high-throughput sequencing and assessment of physiological and biochemical responses in order to evaluate the impacts of MeHg exposure on rice growth, stress tolerance, and underlying molecular mechanisms. The results showed that significant increases in root-to-stem translocation of MeHg occurred, further inducing oxidative stress, as evidenced by alterations in antioxidant enzyme activities (CAT, POD, and SOD), proline (PRO) content, and chlorophyll levels, resulting in cellular damage and stunted plant growth. Transcriptome analysis identified differentially expressed miRNAs (DE-miRNAs) in rice roots associated with metabolic regulation, signal transduction, biosynthesis, and plant-pathogen interactions. Notably, genes involved in starch and sucrose metabolism, the Target of Rapamycin (TOR) signaling pathways, and phenylpropanoid biosynthesis were found to be key in rice's response to MeHg toxicity. Protein-protein interaction (PPI) and miRNA-target gene analyses further highlighted genes encoding jasmonic acid-amido synthetase and FERONIA-like receptors as potential candidates for detoxification mechanisms. This study contributes to building the molecular regulation network and physiological underpinnings of rice's response to MeHg stress, providing insights into potential targets for genetic improvement to enhance rice's resilience to MeHg toxicity.