MdMYB10 affects nitrogen uptake and reallocation by regulating the nitrate transporter MdNRT2.4–1 in the red flesh apple

Nitrate is the major nitrogen source for higher plants. In addition to serving as a nutrient, it is also a signaling molecule that regulates plant growth and development. Although membrane-bound nitrate transporter/peptide transporters (NRT/PTRs) have been extensively studied and shown to regulate nitrate uptake and movement, little is known about how these factors are regulated by the external nitrogen environment. Red-fleshed apple, whose coloration is determined by the transcription factor MdMYB10, had higher nitrate uptake efficiency than non-red-fleshed apple. Nitrate assimilation and utilization were higher in red-fleshed apple cultivars, and comparative transcriptome analysis showed that the expression of genes encoding the NRT2s was increased in red-fleshed apple. In vitro and in vivo experiments showed that MdMYB10 directly bound to the MdNRT2.4-1 promoter to transcriptionally activate its expression, resulting in enhanced nitrate uptake. MdMYB10 also controlled nitrate reallocation from old leaves to new leaves through MdNRT2.4-1. Overall, our findings provide novel insights into the mechanism by which MdMYB10 controls nitrate uptake and reallocation in apple, which facilitates adaptation to a low-nitrogen environment.