Physiological, Transcriptional, and Metabolic Responses Associated with Pyrophosphate-Mediated Alleviation of Cadmium Stress in Arabidopsis.

Pyrophosphate serves as a vital reagent for the chemical remediation of soil heavy metal contamination. However, reports regarding how pyrophosphate regulates plant cadmium (Cd) tolerance at the physiological level remain scarce. In this study, we combined phenotypic, physiological, transcriptomic, and metabolomic approaches to comprehensively elucidate the response of Arabidopsis to Cd stress mediated by sodium pyrophosphate (Na-PPi). The results demonstrated that oxidative stress triggered by Cd significantly suppressed the growth of Arabidopsis seedlings. In contrast, exogenous Na-PPi effectively lowered the contents of MDA, H2O2, and O2•-, and concurrently diminished Cd accumulation in the plants under the Cd stress condition. Meanwhile, Na-PPi significantly altered the expression of genes associated with "phenylpropanoid biosynthesis" and "cell wall biosynthesis". Furthermore, Na-PPi application under Cd stress significantly enhanced the expression of the nitrate transporter genes NRT2.1 and NRT2.6 and promoted nitrogen accumulation in Arabidopsis plants. Metabolomic analysis revealed that Na-PPi significantly altered the metabolic profile of Arabidopsis under Cd stress, increasing the accumulation of polydatin while decreasing the levels of nicotinic acid, baicalin, camalexin, and glutathione. These findings provide a crucial scientific basis for a deeper understanding of pyrophosphate-mediated heavy metal soil remediation from a plant-level perspective.