Summary: The Plant Cell, Vol. 4, 1229-1236, October 1992O 1992American Society of Plant Physiologists
Regulationof Flavonoid Biosynthetic Genes in Germinating- -
William L. Kubasek,a Brenda W. Shirley,'?' Ann McKillop,b Howard M. Goodman,' Winslow Briggs,b
and Frederick M. Ausubel,ay2
a Department of Genetics, Harvard Medical School, and Department of Molecular Biology, Massachusetts General Hospital,
Carnegie lnstitutionof Washington, Department of Plant Biology, Stanford, California94350
Many higher plants, including Arabidopsis, transiently display purple anthocyaninpigmentsjust after seed germination.
We observedthat steadystate levelsof mRNAsencoded byfour flavonoidbiosyntheticgenes, PAL7 (encodingphenylala-
nine ammonia-lyase l),CHS (encoding chalcone synthase), CHI (encoding chalcone isomerase), and DFR (encoding
dihydroflavonolreductase), were temporally regulated, peaking in 3-day-oldseedlings grown in continuous white light.
Except for the case of PAL7 mRNA, mRNA levels for these flavonoidgenes were very low in seedlingsgrown in darkness.
Light induction studies using seedlings grown in darkness showed that PALI mRNA began to accumulate before CHS
and CHI mRNAs, which, in turn, began to accumulate before DFR mRNA. This order of induction is the same as the
order of the biosynthetic steps in flavonoid biosynthesis. Our results suggest that the flavonoid biosynthetic pathway
is coordinately regulated by a developmentaltiming mechanism during germination. Blue light and UVB light induction
experiments using red light- and dark-grownseedlings showed that the flavonoid biosynthetic genes are induced most
effectively by UVB light and that blue light induction is mediated by a specific blue light receptor.