14-3-3λ Affects Production of a Sinapoyl Derivative in Lignin Biosynthesis during Drought Stress in Arabidopsis Thaliana

Abstract

The phenylpropanoid biosynthetic pathways have been targeted for bio-engineering as compounds produced by this pathway are known for anti-oxidant, anti-viral, anti-inflammatory, anti-allergenic, vasodilatory activities as well as response to various stresses in plants. Our interest is to study how drought stress influences biosynthesis of flavonoids and lignin monomers in this pathway and the roles of candidate regulatory enzymes such as 14-3-3 proteins in regulation of these compounds. Our laboratory has identified an isoform (14-3-3 λ) that demonstrates a role in drought stress tolerance and also affects the biosynthesis of flavonoids and lignins. To determine the role of the 14-3-3 λ in the phenylpropanoid pathway, we used a reverse genetics approach, in which the amounts of secondary metabolites produced in a 14-3-3 λ knockout mutant were compared to the wild-type Arabidopsis thaliana (Columbia-0) under normal and drought stress conditions. Using LC-MS, our analyses show that the quantity of sinapoyl derivatives varied significantly between the drought treated 14-3-3 knockouts and the drought treated wild-types. There were significant changes in a sinapoyl derivative and no change in the flavonol glycosides in drought or hydrated samples of the mutants or the wildtype. Gene expression results revealed significant changes under drought conditions in two enzymes involved in lignin biosynthesis: phenyl alanine lyase (PAL) and Caffeoyl Coenzyme A 3-O-methyltransferase 1 (COMT). The metabolite profile and gene expression data indicate that 14-3-3λ is affected genes in the lignin biosynthesis and flavonoid biosynthesis pathways.