Phenylpropanoid compounds in primary leaf tissues of rye (Secale cereale). Light response of their metabolism and the possible role in UV‐B protection

Abstract

Phenylpropanoid compounds in primary leaf tissues of rye {Secale cereale). Light response of their metabolism and the possible role in UV-B protection. -Physiol. Plant. 97; 160-168.The present study was undertaken in order to investigate the suitability of certain markers for UV plant response. In addition, we attempted to link the intemal tissue distribution of specific UV-absorbing compounds to profiles of radiation gradients within intact primary rye leaves {Secale cereale L, cv. Kustro), Etiolated rye seedlings irradiated wift low visible light (LL) and/or UV radiation were used to study enzyme activities of the two key enzymes, phenylalanine ammonia-lyase (PAL) and chalcone synthase (CHS), together with the tissue-specific accumulation of soluhle phenylpropanoid products. Plants grown under relatively high visible light (HL) with or without supplementary UV-B radiation were used for further characterization. Apparent quantum yield and fluorescence quenching parameters were monitored to assess potential physiological changes due to UV-B exposure in HL-grown seedlings. A quartz fibreoptic microprobe was used to characterize the intemal UV-B gradient of the leaf. The response of the phenylpropanoid metabolism to UV radiation was similar in primary' leaves of both etiolated and HL-treated green plants. The epidermis-specific fla-vOTioids together with CHS activity tumed out to be suitable markers for assessing the effect of UV on the phenolic metabolism. The functional role of phenyipropanoid compounds was strongly implicated in protecting rye from UV-B radiation.

UV-B-mediated flavonoid synthesis in white asparagus (Asparagus officinalis L.)

“…Enhancing activities of both PAL and POD after UV-B irradiation seem to be a key factor in the defence system, protecting tissues against oxidative stress and cell damage (Rao, Paliyath, & Ormrod, 1996;Reuber, Bornman, & Weissenböck, 2006;Sarma & Sharma, 1999;Yannarelli et al, 2006). However, both enzymes differed in their response with regard to adaptation time.…”

The role of UDP-glucose:hydroxycinnamate glucosyltransferases in phenylpropanoid metabolism and the response to UV-B radiation in Arabidopsis thaliana

“…To alleviate the damaging eVects of enhanced UV-B radiation, plants make use of UV-screening pigments (Lois 1994;Reuber et al 1996;Bharti and Khurana 1997;Bieza and Lois 2001). For Arabidopsis, the role of Xavonoids and sinapate esters in UV-B stress adaptation was deduced from the analysis of mutants impaired in the biosynthesis of these compounds like transparent testa tt4 and tt5 (Li et al 1993) or fah1 (Chapple et al 1992;Landry et al 1995;Sheahan 1996).…”

Adequate phenylalanine synthesis mediated by G protein is critical for protection from UV radiation damage in young etiolated Arabidopsis thaliana seedlings

“…Among the most important means of preventing damage from exposure to UV-B is the prophylactic deployment of UV-screening pigments that derive from the phenylpropanoid pathway. In most plants, exposure to UV-B results in the increased or new synthesis of such screening pigments (Li et al 1993;Stapleton & Walbot 1994;Caldwell et al 1995;Landry, Chapple & Last 1995;Christie & Jenkins 1996;Gonzalez et al 1996;Reuber, Bornman & Weissenböck 1996;Rozema et al 1997;Burchard, Bilger & Rozema et al 2002;Weinig et al 2004;Casati & Walbot 2005).…”