Abscisic acid reduces Cd accumulation by regulating Cd transport and cell wall sequestration in rice

Cadmium (Cd) uptake by rice plants and its subsequent movement through food chains pose a notable risk to the health of both plants and humans. Therefore, understanding the fundamental mechanisms underlying the uptake and movement process is essential. Through transcriptome analysis, we found that numerous abscisic acid (ABA)-related genes responded to Cd stress. Exogenous application of ABA significantly reduced Cd accumulation in the shoots and roots of rice plants. The increased ascorbate peroxidase (APX) enzyme activity, decreased H2O2 content, and elevated Cd tolerance index collectively suggest that ABA may mitigate the toxicity of Cd in rice plants. Further study revealed that exogenous ABA reduced Cd accumulation by regulating Cd transport and cell wall sequestration. Consistently, mutation of the ABA signaling factor OsABI5 resulted in a significant increase in Cd accumulation in shoots. Moreover, foliar spraying of ABA during the grain-filling stage significantly reduced Cd accumulation in rice grains, which was attributed mainly to decreased Cd uptake and the inhibition of Cd transportation from roots to shoots and from leaves to grains. These findings elucidate the underlying mechanisms of the ABA-mediated response to Cd stress in rice and provide a practical reference for coping with Cd pollution in farmlands.