Tissue Localization of u.v.-B-Screening Pigments and of Chalcone Synthase mRNA in Needles of Scots Pine Seedlings

• Published in: The New phytologist Vol. 132; no. 2; pp. 247 - 258
• Main Authors: Schnitzler, Jorg-Peter, Jungblut, Tim P., Heller, Werner, Kofferlein, Matthias, Hutzler, Peter, Heinzmann, Ulrich, Schmelzer, Elmon, Ernst, Dieter, Langebartels, Christian, Sandermann, Heinrich
• Format: Journal Article
• Language: English
• Published: Oxford, UK Cambridge University Press 01.02.1996; Blackwell Publishing Ltd; Blackwell
• Subjects: Agricultural and forest climatology and meteorology. Irrigation. Drainage; Agricultural and forest meteorology; Agronomy. Soil science and plant productions; Animal, plant and microbial ecology; Applied ecology; Biological and medical sciences; Cell walls; chalcone synthase; Climatic adaptation. Acclimatization; Cotyledons; Ecotoxicology, biological effects of pollution; Effects of pollution and side effects of pesticides on plants and fungi; epidermal layer; Flavonoids; Flavonols; Fluorescence; Fundamental and applied biological sciences. Psychology; General agronomy. Plant production; Glycosides; in situ hybridization; Lignin; Metabolism; Metabolism. Physicochemical requirements; Pine trees; Pinus sylvestris (Scots pine) seedlings; Plant physiology and development; Plants; Seedlings; u.v.‐B irradiation and flavonoid localization; Plant tissue; Acyltransferases; Enzyme; UVB radiation; Transferases; Epidermis; Plant leaf; Pinus sylvestris; Flavonoid; Messenger RNA; Naringenin-chalcone synthase; Softwood forest tree; Gymnospermae; Pigments; Coniferales; Spermatophyta; Localization
• ISSN: 0028-646X; 1469-8137
• DOI: 10.1111/j.1469-8137.1996.tb01844.x

Epidermal tissue was isolated from Scots pine (Pinus sylvestris L.) needles by enzymatic digestion in order to study tissue distribution of u.v.-B-screening pigments. Up to 90% of the needle content of a group of diacylated flavonol glycosides that were structurally closely related was found in the epidermal layer. Among these metabolites, 3'',6''-di-para-coumaroyl-isoquercitrin and 3'',6''-di-para-coumaroyl-astragalin were the main u.v.-B-induced compounds in cotyledons and primary needles, respectively. However, catechin and astragalin (kaempferol 3-glucoside), two non-acylated flavonoid metabolites, were only observed in total needle extracts, and at levels independent of u.v.-B treatment. According to this metabolite distribution, the mRNA of chalcone synthase, the key enzyme to flavonoids, was found in epidermal and mesophyll as well as vascular tissues. The major alkaliextractable wall-bound phenolic metabolites, astragalin, 4-coumaric acid, and ferulic acid, a minor component of the cell wall, were also found exclusively in the epidermal layer. These compounds were not stimulated by u.v.-B irradiation within the experimental period. Staining of needle cross sections and epidermal layer preparations with Naturstoffreagenz A confirmed the specific localization of wall-bound astragalin in the outer wall of the epidermal layer. Model calculations of u.v.-B absorptions at 300 nm of soluble and cell-wall-bound metabolites of the epidermal layer revealed an almost complete shielding of the mesophyll tissue from u.v.-B radiation.