The MYB-bHLH-NRAMP module modulates the cadmium sensitivity of quinoa by regulating cadmium transport and absorption.

Cadmium (Cd) is one of the most dangerous environmental pollutants and is easily absorbed by food crops. Quinoa is a kind of coarse grain crop with rich nutrition and strong stress resistance, which is easy to accumulate Cd. The increasingly serious soil Cd pollution poses a serious threat to the food safety of quinoa. However, there are very limited reports on Cd absorption and transport in quinoa. The identification and functional analysis of Cd absorption and transport proteins are essential for improving the food safety of quinoa. In this study, the key transporter CqNRAMP1 potentially involved in Cd uptake was identified from quinoa by expression detection. Yeast complementation test found that CqNRAMP1 has the ability to transport metal ions in yeast. Using transgenic technology, it was found that CqNRAMP1 enhanced the sensitivity of quinoa to Cd stress by promoting Cd absorption. The transcription factors CqMYB26 and CqbHLH162 that potentially regulate CqNRAMP1 were identified from the quinoa genome by bioinformatics. Physiological and biochemical, yeast two-hybrid, bimolecular fluorescence complementation and dual luciferase experiments further found that CqMYB26 and CqbHLH162 enhanced the expression of CqNRAMP1 through protein-protein interaction, thus promoting Cd absorption and further enhancing the sensitivity of quinoa to Cd exposure. This study explored the molecular mechanism of CqMYB26-CqbHLH162 promoting the expression of CqNRAMP1 and regulating Cd absorption by physiological, biochemical and molecular biological techniques. These research findings will offer a crucial theoretical foundation and practical insight for cultivating low Cd-accumulating crops and addressing food safety concerns.