A flavonol synthase (FLS) gene, GhFLS1, was screened out increasing salt resistance in cotton

Background Flavonols play important roles in antioxidation and anticancer activities, longevity, and cardiovascular protection. Flavonol synthase (FLS) is a key enzyme for flavonol synthesis. Result Phenotypic, transcriptional and metabolic data were analyzed, which showed that there was a close relationship between salt stress and flavonoids, and flavonols were significantly upregulated under salt stress. Nine, seven, four, and four FLS genes were identified in Gossypium hirsutum, Gossypium barbadense, Gossypium arboreum, and Gossypium raimondii, respectively. The results of subcellular localization showed that FLS existed in the nucleus and cytoplasmic. Through phylogenetic analysis, 24 FLS genes were divided into three subfamilies. The results of the RNA sequencing showed that the expression of GhFLS genes was mainly induced by salt, drought, low temperature, and heat stress. GhFLS promoter mainly comprised plant hormone response elements and abiotic stress elements, indicating that the GhFLS gene may play a key role in abiotic stress response. The proline contents of pYL156:GhFLS1 was reduced significantly compared to pYL156 under salt stress, thereby reducing the resistance of cotton to salt stress. Conclusion This study will lay a foundation for further study on the antioxidant regulation mechanism of the FLS gene under abiotic stress.