Ultrasound and trehalose differentially modulate metabolic allocation to improve nutritional quality in mustard (Brassica juncea) sprouts

Mustard ( Brassica juncea ) sprouts are recognized for their high nutritional and functional value. Here, the effects of ultrasound, trehalose, and their combined treatment on mustard metabolic traits were evaluated for improving sprout quality. Ultrasound promoted germination and increased soluble protein, flavonoid and glucosinolate levels. Trehalose primarily elevated soluble sugars, ascorbic acid and total phenolics. In contrast, the combined treatment reduced antioxidant capacity and decreased the glucosinolates content, indicating a metabolic trade-off. Transcriptome analysis revealed shifts in carbohydrate metabolism, diversion of phenylpropanoid flux towards flavonoid biosynthesis and suppression of glucosinolate biosynthetic genes. The transcription factors JUB1 , ARF32 and NAC59 were identified as potential regulators. Overall, ultrasound was more effective than trehalose in enhancing functional nutrient quality, and single elicitors were preferable to combined application for targeted improvement of mustard sprout nutritional value. • Ultrasound and trehalose altered primary and secondary metabolism in mustard sprouts. • Ultrasound enhanced germination and increased flavonoid and glucosinolate contents. • Trehalose treatment mainly improved soluble sugars and antioxidant capacity. • The combined treatment did not produce superior quality improvement.