Over the past 25 years the Winkel laboratory has helped establish the flavonoid pathway as a model for studying the macromolecular and intracellular organization of plant metabolism. They were the first to demonstrate direct protein interactions among flavonoid enzymes and also uncovered the unexpected localization of flavonoid enzymes in the nucleus.  Most recently, they showed that the entry-point enzyme, chalcone synthase (CHS), interacts with components of the histone remodeling machinery that may offer a new explanation for the connection between flavonoid enzymes and defense.  

To further explore the potential impact of CHS on gene expression, an RNA-seq dataset was generated for an Arabidopsis tt4 mutant line, which lacks the enzyme and is devoid of flavonoids.  This experiment identified numerous transcripts with altered levels in tt4 seedlings.  Surprisingly, a substantial number of these encode components of the core circadian clock, including the key transcriptional regulators, CCA1 and TOC1.  Analysis of CCA1p::luciferase and TOC1p::luciferase reporter constructs further showed that the amplitude, but not the phase, of the circadian cycle is altered in CHS-deficient seedlings.  Similar effects were observed for a tt7 mutant allele, which affects an intermediate step in flavonoid metabolism, implicating dihydroxy flavonoids rather than the CHS enzyme in modulation of the clock.  Current experiments are aimed at understanding the mechanisms underlying this intriguing newly-discovered connection between flavonoids and the circadian circuitry in plants, which has recently also been reported in animal systems.

Bio: Brenda Winkel is a Professor and former Head of Biological Sciences at Virginia Tech in the U.S. She is currently on Research Leave as a TULIP Visiting Scientist with Elodie Gaulin in the IPM team of Bernard Dumas.