Shading enhances Se accumulation in tea leaves through promoting CsMYB7-like-mediated conversion of Se (VI) to Se (IV).

Limited selenium (Se) accumulation in agricultural products contributes to widespread dietary Se deficiency, posing a global nutritional threat. Efficient agronomic strategies to enhance Se biofortification in crops are still lacking. Here, we reveal the synergistic effects of shading and Se nanoparticles application on Se biofortification in tea leaves. Field experiments demonstrate that shading enhances Se accumulation in tea leaves under sufficient Se supply, through activating Se metabolism pathway. We identify CsAPR1 functions at the early stage of Se assimilation, catalyzing the reduction of Se (VI). The transcription of CsAPR1 is activated by CsMYB7-like and is further promoted by shading through interaction with CsbHLH70. Under sunlight, CsHY5 competes with CsbHLH70 for binding to CsMYB7-like, thereby attenuating CsMYB7-like-mediated transcription of CsAPR1 and suppressing Se accumulation in tea plants. Our findings reveal the molecular mechanisms underlying shade-induced enhancement of Se biofortification, offering insights and strategies for Se-enriched crop production.