Cotton sprouts as potential vegetable source: Nutrient compositions and alterations in metabolomics and transcriptomics between light and dark growth conditions

Cottonseed is a by-product of cotton industry, but its broad application in human diets has not been fully elucidated. This study aims to analyse the nutritional composition of cotton sprouts and investigate metabolic and transcriptomic differences under light and darkness. The findings revealed that the glanded ZM41 yellow cotton sprouts were rich in protein (2.8 %), vitamin E (0.443 mg/100 g), and minerals, with < 0.01 % free gossypol. Moreover, protein, aspartic acid (1,026 mg/100 g), and serine (136 mg/100 g) reached their highest levels in nine-day-old sprouts, while no significant differences were observed in the other nutrients on the 7th, 9th, or 11th day. The average quantitative values of 64 cottonseed varieties found gossypol (27.9 mg/kg), protein (3.6 %), potassium (1,487.3 mg/kg), calcium (506.2 mg/kg) and magnesium (330.2 mg/kg). Integrated metabolome and transcriptome analyses revealed that 317 out of 1,880 metabolites were differentially accumulated between light and dark conditions, wherein the downregulation of structural genes encoding CHI, F3H, FLS, DFR, F3 ' H, ANS, LAR and ANR resulted in decreased flavonoid levels in dark-cultivated sprouts, while the upregulation of HMGR and 2-ODD-1 enhanced the biosynthesis of gossypol. This study provides insights into the nutritional and metabolic aspects of cotton sprouts, offering a reference for potential commercial applications.