Phosphorylation of TabZIP27 by TaCIPK16 Regulates TaMAN7-4B Expression During Cadmium Response in Wheat

Cadmium (Cd) contamination poses a significant threat to wheat productivity and food safety. This study demonstrates that TaMAN7-4B, which encodes an endo-β-mannanase involved in the metabolism of cell wall mannans, is significantly upregulated in response to Cd stress, thereby enhancing Cd tolerance by increasing the root cell wall mannan content and facilitating Cd sequestration. Furthermore, we identified the transcription factor TabZIP27 as a direct regulator of TaMAN7-4B expression. TabZIP27 is phosphorylated by the kinase TaCIPK16, which stabilizes TabZIP27 by suppressing its proteasome-dependent degradation. This phosphorylation event subsequently promotes the transcription of TaMAN7-4B, resulting in enhanced Cd binding within the root cell walls and reduced translocation of Cd from roots to shoots. Our findings elucidate a novel regulatory module, TaCIPK16-TabZIP27-TaMAN7-4B, which governs Cd accumulation in wheat, thereby providing potential targets for the breeding of low-Cd cultivars.