Simulated solar irradiation with enhanced UV-B adjust plastid- and thylakoid-associated polyamine changes for UV-B protection

Abstract

Polyamines have been described to protect against numerous oxidative stresses in plants. Increasing UV-B radiation (280-315 nm) in the biosphere may also induce an increase in radical formation in tissues. This study employed the tobacco cultivars Bel B and Bel W3 to describe possible protective functions of polyamines against UV-B radiation in sun light simulators (GSF/Munich) with natural diurnal fluctuations of simulated UV-B. Polyamine measurements on a whole leaf basis in isolated chloroplasts and thylakoids were paralleled to photosynthetic and respiration rates, photosynthetic efficiency, leaf thickness and photosynthetic pigment compositions. The study revealed that an increase of polyamines, and especially of putrescine level in thylakoid membranes upon elevated UV-B exposure comprises one of the primary protective mechanisms in the photosynthetic apparatus of the tobacco variety Bel B against UV-B radiation. The tobacco cultivar Bel W3, sensitive to ozone, was also proved to be sensitive to UV-B. This sensitivity is attributed to its incapability to enhance putrescine level in thylakoid membranes. After prolongation of UV-B exposure, when endogenous plant balances are being gradually restored, due to secondary responses, (e.g., biosynthesis of carotenoids and of additional flavonoids) and the plant is adapting to the altered environmental conditions, then the polyamine level is being reduced. Thus, we can discriminate the UV-B induced stress period from a UV-B acclimation period.

Fast and reversible response of thylakoid-associated polyamines during and after UV-B stress: a comparative study of the wild type and a mutant lacking chlorophyll b of unicellular green alga Scenedesmus obliquus

“…2a, b). This is in line with many previous reports showing a detrimental effect of UV-B on the PSII activity in higher plants (Melis et al 1992;Lütz et al 2005) and algae (Lütz et al 1997;Häder et al 2001;White and Jahnke 2002). The small functional antenna during short term UV-B exposure protects the maximal quantum efficiency of PSII both in terms of percentage reduction within 3 hours of exposure (39% for Wt-lhc vs. Tables 1 and 2 1999; Polle et al 2003).…”

“…It is suggested that PAs are prevalently bound to chl b in a light-dependent manner, by a presumptive coordination linkage of uncharged PA with Mg 2+ of the tetrapyrrole ring, independent of TGase catalysis (Della Mea et al 2004). Furthermore, low PA titer results in higher sensitivity to environmental stresses (Ormrod and Beckerson 1986;Kramer et al 1991;Scalet et al 1995;Navakoudis et al 2003;Lütz et al 2005), while increase of PA titer confers tolerance to stress. Whether the Wt-lhc response to UV-B radiation could be reversed upon PA artificial elevation, as it was demonstrated for the Wt (Sfichi et al 2004), is a matter of further investigation.…”

Polyamines: potent modulators of plant responses to stress

“…foliage, and plant height whereas, levels of PAs increased which was depend on the dose of UV-B radiation but prolonged exposure to UV-B reduced the level of PA. An increase of PAs and especially that of Put in thylakoid membranes upon exposure of UV-B radiations was observed in the tobacco variety Bel B, while the cultivar Bel W3, sensitive to UV-B, was incapable to enhance Put level in thylakoid membranes, which may be attributed to its sensitivity (Lutz et al 2005). Moreover, on prolonged exposure of plants to UV-B radiations the PAs level declined and developed other secondary responses such as biosynthesis of carotenoides and flavonoids.…”

Endogenous polyamines lessen membrane damages in pea plants provoked by enhanced ultraviolet-C radiation

“…Relatively limited information concerning the role of plant PAs toward UV irradiation has been published. Some articles demonstrate changes in PA concentration after UV-B treatment of cucumber (Kramer et al 1991;An et al 2004), soybean (Kramer et al 1992), Phaseolus vulgaris (Smith et al 2001) and tobacco (Lütz et al 2005). In contrast to UV-B, the effect of UV-C radiation on endogenous PAs has been studied only in fruit tissue (Stevens et al 1998;Maharaj et al 1999;GonzalezAguilar et al 2001GonzalezAguilar et al , 2004 and tobacco callus (Zacchini and de Agazio 2004).…”