Phenylpropanoid pathway intermediates regulate transient expression of a chalcone synthase gene promoter.
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 (greater than 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' 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.
Loake
G J
GJ
Plant Biology Division, Samuel Roberts Noble Foundation, Ardmore, Oklahoma 73402.
Choudhary
A D
AD
Harrison
M J
MJ
Mavandad
M
M
Lamb
C J
CJ
Dixon
R A
RA
D000217:Acyltransferases / Q000235:genetics*; D001483:Base Sequence; D002478:Cells, Cultured; D002678:Chimera; D015500:Chloramphenicol O-Acetyltransferase / Q000235:genetics; D002934:Cinnamates / Q000138:chemical synthesis / Q000494:pharmacology; D003001:Cloning, Molecular; D003373:Coumaric Acids / Q000494:pharmacology; D004247:DNA; D015971:Gene Expression Regulation, Enzymologic; D000455:Medicago sativa / Q000235:genetics; D008969:Molecular Sequence Data; D010666:Phenylpropionates / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D011523:Protoplasts
D002934:Cinnamates; D003373:Coumaric Acids; D010666:Phenylpropionates; C029010:cinnamic acid; D004247:DNA; D000217:Acyltransferases; D015500:Chloramphenicol O-Acetyltransferase; C020141:flavanone synthetase