THE PLANT CELL, Vol 3, Issue 8 829-840, Copyright © 1991 by American Society of Plant Biologists
Phenylpropanoid Pathway Intermediates Regulate Transient Expression of a Chalcone Synthase Gene Promoter
G. J. Loake, A. D. Choudhary, M. J. Harrison, M. Mavandad, C. J. Lamb and R. A. Dixon
Plant Biology Division, The Samuel Roberts Noble Foundation, P.O. Box 2180, Ardmore, Oklahoma 73402
A chimeric gene construct containing a bean chalcone synthase (CHS)
promoter fused to the chloramphenicol acetyltransferase (CAT) reporter gene
was strongly expressed when electroporated into alfalfa protoplasts that
were then exposed to a fungal elicitor. Low concentrations (5 x 10-6 to
10-4 M) of exogenously applied trans-cinnamic acid (CA), the first
intermediate of the phenylpropanoid pathway, slightly stimulated
elicitor-induced CAT expression, whereas high concentrations (>10-4 M)
severely reduced expression to below the levels observed in the absence of
elicitor. In contrast, trans-p-coumaric acid (4-CA, the second intermediate
in the pathway) stimulated expression from the CHS promoter up to 4.5-fold
at 5 x 10-4 M. Expression of CAT driven by the promoters of other
elicitor-inducible defense response genes was not markedly affected by CA
or 4-CA. Stimulation of CHS promoter expression by low concentrations of CA
and 4-CA was completely abolished by 5[prime] deletion to position -130,
but not -174. When the -180 to -130 region of the CHS15 promoter was
coelectroporated into elicited protoplasts on a separate plasmid along with
the intact -326 CHS-CAT construct, the decreased CAT expression as a
function of CA or 4-CA concentration was consistent with the
coelectroporated sequence competing in trans with the intact promoter for
the binding of a factor(s) involved in the up regulation of CHS
transcription by 4-CA and low concentrations of CA. Our data support the
hypothesis that phenylpropanoid compounds may act as natural and specific
regulators of plant gene expression and define the location of a cis-acting
element in the CHS15 promoter involved in the induction by phenylpropanoid
pathway intermediates.
