Increased ABA synthesis by overexpression of Cd-NAC ameliorates cadmium toxicity in vegetable soybean.

Cadmium (Cd) stress is a significant threat to crop production. Abscisic acid (ABA) has been recognized for its ability to mitigate Cd toxicity. However, the underlying regulatory mechanisms governing ABA biosynthesis and its signaling pathway in response to Cd stress remain elusive. Here, we identified a Cd-induced NAC1 transcription factor (Cd-NAC) from vegetable soybean, which played a pivotal role in this process. Overexpression of Cd-NAC in transgenic vegetable soybean roots resulted in enhanced Cd tolerance, manifested by longer roots and higher biomass compared to Cd-NAC knockdown plants. Cd-NAC functions as a nuclear transcription factor that binds directly to the promoters of the 9-cis-epoxycarotenoid dioxygenase coding genes (GmNCED3.1 and GmNCED3.2), thereby activating their transcription and promoting the biosynthesis of ABA. Our findings uncover a crucial molecular mechanism of ABA conferring Cd tolerance in plants, which holds promise for sustainable agricultural production and effective management of this hazardous heavy metal, ultimately contributing to improved environmental management and ecosystem function.