Flavonols contrary affect the interconnected glucosinolate and camalexin biosynthesis pathway in Arabidopsis thaliana

Flavonols are structurally and functionally diverse molecules playing roles in plant biotic and abiotic stress tolerance, auxin transport inhibition, pollen development, etc. Despite their ubiquitous occurrence in land plants and multifunctionality, the effect of perturbation of flavonol biosynthesis over global gene expression and pathways other than flavonoid biosynthesis has not been studied in detail. To understand the signaling role of different flavonol metabolites, herein, we used the flavonol deficient Arabidopsis thaliana loss-of-function mutant flavonol synthase1 (fls1-3) as object of study. Comparative transcriptome and metabolic profiling were used to study the effects of genetic flavonol deficiency and exogenous supplementation with flavonol derivatives (kaempferol, quercetin and rutin) on different cellular processes in the seedling. Various flavonol biosynthesis-related regulatory and structural genes were found to be up-regulated in the fls1-3 mutant which could be reversed by exogenous flavonol feeding. Our manifold comparative studies indicated the modulation of various biological processes and metabolic pathways by flavonols. Camalexin biosynthesis was found to be negatively regulated by flavonols. Interestingly, flavonols appeared to promote the accumulation of aliphatic glucosinolate through transcription factor-mediated up-regulation of biosynthesis genes. Overall, this study provides new insights into molecular mechanisms by which flavonols interfere with the relevant signal chains and their molecular targets and adds new knowledge to the expanding plethora of biological activity of flavonols in plants. Significance Comparative transcriptome and metabolomic profiling of genetic flavonol deficiency and exogenous flavonol supplementation in A. thaliana seedlings, for the first-time revealed the inverse regulation of interconnected specialized metabolite pathways by flavonol aglycones, and -glycosides. Flavonols negatively regulate camalexin biosynthesis, while promoting the accumulation of aliphatic glucosinolates. Our study adds new insights into the expanding plethora of biological activity of flavonols in plants and will help to uncover the molecular mechanisms by which flavonols interfere with the relevant signal chains and their molecular targets. ### Competing Interest Statement The authors have declared no competing interest.