SINAPIC ACID ESTER METABOLISM IN WILD-TYPE AND A SINAPOYLGLUCOSE-ACCUMULATING MUTANT OF ARABIDOPSIS

Sinapoylmalate is one of the major phenylpropanoid metabolites that is accumulated in the vegetative tissue of Arabidopsis thaliana. A thin- layer chromatography-based mutant screen identified two allelic mutant lines that accumulated sinapoylglucose in their leaves in place of si napoylmalate. Both mutations were found to be recessive and segregated as single Mendelian genes. These mutants define a new locus called SN G1 for sinapoylglucose accumulator. Plants that are homozygous for the sng1 mutation accumulate normal levels of malate in their leaves but lack detectable levels of the final enzyme in sinapate ester biosynthe sis, sinapoylglucose:malate sinapoyltransferase. A study of wild-type and sng1 seedlings found that sinapic acid ester biosynthesis in Arabi dopsis is developmentally regulated and that the accumulation of sinap ate esters is delayed in sng1 mutant seedlings.