In situ Localization of Phenylpropanoid-Related Gene Expression in Different Tissues of Light- and Dark-Grown Parsley Seedlings

Abstract

Using in situ RNA hybridization and immunohistochemical techniques, we investigated the tissue-specific and light-dependent expression of four genes involved in phenylpropanoid metabolism in various parts o f parsley ( Petroselinum crispum) seedlings.The genes encode phenylalanine amm onia-lyase (PAL) and 4-coum arate: Co A ligase (4 CL), two enzymes of general phenylpropanoid metabolism; chalcone synthase (CHS), the keyenzyme of flavonoid biosynthesis; and bergaptol O-methyltransferase (BMT), a late enzyme of the furanocoumarin pathway. In young leaves, PAL and 4 CL genes were expressed predominantly and in a coordinated fashion in epidermal cells, young xylem cells of vascularbundles, and epithelial cells of oil ducts. The gene(s) encoding BMT wasactive exclusively in the epithelial cells of oil ducts, where as CHS gene expression was largely confined to the epidermis. In shoot and root apices, PAL, 4 CL and CHS m R N A s were detectable at low levels without distinct patterns. The corresponding proteins, however, accumulated preferentially in the protoderm and pith meristem of the shoot apex and in root-cap cells. A gene encoding pathogenesis-related protein 1 (PR 1)was analyzed in rootsfor comparison and was found to be expressed predominantly in the cortical cells o f root tips. The expression o f all genes investigated was, to a greater or lesser extent, dependent on light conditions and tissue age, with highest levels occurring in newly differentiated, light-exposed tissue. In the leaf epidermis o f seedlings illuminated for 20 h, PAL and CHS m R N A s and proteins, as well as 4 CL protein, were particularly abundant. © 2009 Walter de Gruyter. © 1992, Walter de Gruyter. All rights reserved.