title: Effects of enhanced UV-B radiation on hydroxycinnamic acid derivatives extracted from different cell compartments in the aquatic liverwort Jungermannia exsertifolia subsp. cordifolia.
abstract: We examined the responses of ultraviolet-absorbing compounds (UVAC) to enhanced UV-B radiation in the aquatic liverwort Jungermannia exsertifolia subsp. cordifolia for 31 days under laboratory conditions. Samples were exposed to three radiation regimes: P (only photosynthetic radiation), PA (photosynthetic + UV-A radiation) and PAB (photosynthetic + UV-A + UV-B radiation). We measured both the bulk UV absorbance of the methanolic extracts and the levels of individual UVAC. In both cases, the methanol-soluble and the methanol-insoluble, alkali-extractable cell wall-bound fractions were analyzed. The bulk UV absorbance of the soluble fraction was higher than that of the cell wall-bound fraction. The bulk UV absorbances of both fractions increased under enhanced UV-B (PAB regime). Five different hydroxycinnamic acid (HCA) derivatives were found in the soluble fraction and two additional ones in the cell wall-bound fraction, among which only p-coumaroylmalic acid in the soluble fraction and p-coumaric acid in the cell wall-bound fraction increased under enhanced UV-B. The maximum quantum yield of PSII (F(v) /F(m)) decreased and DNA damage (amount of thymine dimers) strongly increased under enhanced UV-B, showing UV-B-induced damage. We conclude that methanol-soluble and cell wall-bound fractions of the liverwort studied have different UVAC, and each individual compound may respond in a different way to UV-B radiation. Thus, the analysis of individual UVAC in both the methanol-soluble and cell wall-bound fractions is advisable to better evaluate the protection mechanisms of liverworts against UV-B radiation. In particular, p-coumaric acid and p-coumaroylmalic acid seem to be especially UV-B responsive and merit further investigation.
authors.affiliation: Complejo Científico-Tecnológico, Universidad de La Rioja, Avda. Madre de Dios 51, 26006 Logroño (La Rioja), Spain.
authors.forename: Gabriel
authors.initials: G
authors.lastname: Fabón
authors.forename: Javier
authors.initials: J
authors.lastname: Martínez-Abaigar
authors.forename: Rafael
authors.initials: R
authors.lastname: Tomás
authors.forename: Encarnación
authors.initials: E
authors.lastname: Núñez-Olivera
mesh_terms: D003373:Coumaric Acids / Q000032:analysis*; D035926:Hepatophyta / Q000737:chemistry* / Q000528:radiation effects*; D010788:Photosynthesis; D014466:Ultraviolet Rays
chemical_list: D003373:Coumaric Acids