The MYC2 and MYB43 Transcription Factors Cooperate to Repress HMA2 and HMA4 Expression, Altering Cadmium Tolerance in Arabidopsis thaliana

Cadmium (Cd) represents a hazardous heavy metal, prevalent in agricultural soil due to industrial and agricultural expansion. Its propensity for being absorbed by edible plants, even at minimal concentrations, and subsequently transferred along the food chain poses significant risks to human health. Accordingly, it is imperative to investigate novel genes and mechanisms that govern Cd tolerance and detoxification in plants. Here, we discovered that the transcription factor MYC2 directly binds to the promoters of HMA2 and HMA4 to repress their expression, thereby altering the distribution of Cd in plant tissues and negatively regulating Cd stress tolerance. Additionally, molecular, biochemical, and genetic analyses revealed that MYC2 interacts and cooperates with MYB43 to negatively regulate the expression of HMA2 and HMA4 and Cd stress tolerance. Notably, under Cd stress conditions, MYC2 undergoes degradation, thereby alleviating its inhibitory effect on HMA2 and HMA4 expression and plant tolerance to Cd stress. Thus, our study highlights the dynamic regulatory role of MYC2, in concert with MYB43, in regulating the expression of HMA2 and HMA4 under both normal and Cd stress conditions. These findings present MYC2 as a promising target for directed breeding efforts aimed at mitigating Cd accumulation in edible plant roots.