Targeted metabolomics and Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry imaging revealed the spatial accumulation of anthocyanins in colored wheat (Triticum aestivum L.) in response to nitrogen application

Abstract

Colored wheat is valued for its high antioxidant and anthocyanin levels, yet the spatial distribution of grain quality under nitrogen (N) application remains unclear. This study analyzed purple (QH2) and blue (QL1) wheat using targeted metabolomics and Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry (MALDI-MS) imaging under two N levels (0 and 240 kg ha−1). Nitrogen increased grain yield and protein content in both varieties but differentially affected anthocyanins, enhancing their accumulation in QH2 while reducing them in QL1. Anthocyanins were mainly localized in the episperm of QH2, dominated by cyanidin-3-O-(6-O-malonyl-β-D-glucoside), whereas in QL1 they were concentrated in the aleurone with delphinidin-3-O-rutinoside as the major component. MALDI-MS imaging showed metabolic up-regulated in the episperm of QH2 and widespread down-regulated across tissues in QL1. These metabolites were enriched in pathways related to secondary metabolism. The findings reveal spatial metabolic responses of colored wheat to N supply and support targeted nutritional improvement.