Investigation of flavonoid expression and metabolite content patterns during seed formation of Artemisia sphaerocephala Krasch.

Abstract Flavonoids are a group of phenolic secondary metabolites in plants that have important physiological, ecological and economic value. In this study, using the desert plant Artemisia sphaerocephala Krasch. as the sample material, the content and components of the total flavonoids in its seeds at seven different developmental stages were determined. In addition, the genes involved in flavonoid metabolism were identified by full-length transcriptome sequencing (third-generation sequencing technology based on PacBio RS II). Their expression levels were analysed by RNA-seq short reading sequencing, to reveal the patterns and regulation mechanisms of flavonoid accumulation during seed development. The key results were as follows: the content of total flavonoids in mature seeds was 15.05 mg g −1 , including five subclasses: flavonols, chalcones, flavones, flavanones and proanthocyanidins, among which flavonols accounted for 45.78%. The period of rapid accumulation of flavonoids was 40–70 d following anthesis. The high expression of phenylalanine ammonia-lyase ( PAL ), 4-coumarate-CoA ligase ( 4CL ) and UDP-glucose:flavonoids 3-o-glucosyltransferase ( UF3GT ) promoted the accumulation of total flavonoids, while the high expression of flavonoids 3′-hydroxylase ( F3′H) and flavonols synthase ( FLS ) made flavanols the main component. Transcription factors such as the MYB-bHLH-WDR ( MBW ) complex and Selenium-binding protein ( SBP ) directly regulated the structural genes of flavonoid metabolism, while C2H2-type zinc finger ( C2H2 ), Zinc-finger transcription factor ( GATA ), Dehydration-responsive element binding ( DREB ), Global Transcription factor Group E protein ( GTE ), Trihelix DNA-binding factors ( Trihelix ) and Phytochrome-interacting factor ( PIF ) indirectly promoted the synthesis of flavonoids through hormones such as brassinoidsteroids (BRs) and abscisic acid (ABA). These results provided valuable resources for the application of related genes in genetics and breeding.