Thylakoid‐associated Polyamines Adjust the UV‐B Sensitivity of the Photosynthetic Apparatus by Means of Light‐harvesting Complex II Changes^¶

Abstract

The sensitivity of the photosynthetic apparatus to ultraviolet‐B (UV‐B) irradiation was studied in cultures of unicellular green alga Scenedesmus obliquus incubated in low light (low photosynthetically active radiation intensity [LL]) and high light (high photosynthetically active radiation intensity [HL]) conditions, treated or not with exogenous polyamines. Biochemical and physicochemical measurement showed that UV‐B radiation induces a decrease in the thylakoid‐associated putrescine (Put) and an increase in spermine (Spm), so that the reduction of Put/Spm ratio leads to the increase of light‐harvesting complex II (LHCII) size per active reaction center and, consequently, the amplification of UV‐B effects of the photosynthetic apparatus. The separation of oligomeric and monomeric froms of LHCII from isolated thylakoids showed that UV‐B induces an increase in the oligomeric forms of LHCII, which was more intense in LL than in HL. By manipulating the LHCII size with exogenous polyamines, the sensitivity degree of the photosynthetic apparatus to UV‐B changed significantly. Specifically, the addition of Put decreased highly the sensitivity of LL culture to UV‐B because of the inhibitory effect of Put on the LHCII size increasing, wheres the addition of Spm enhanced the UV‐B injury induced in HL culture because of the increasing of LHCII size. The ability of the photosynthetic apparatus to recover the UV‐B induced changes was also investigated.

Spatial and Temporal Distribution of Polyamine Levels and Polyamine Anabolism in Different Organs/Tissues of the Tobacco Plant. Correlations with Age, Cell Division/Expansion, and Differentiation

“…In this context, PAs could act either as carbon/nitrogen reserves or as signal molecule(s) regulating senescence and probably sink-source relationships. Also, PAs are present in thylakoid membranes, PSII, and the lightharvesting complex (Kotzabasis et al, 1993b;Sfichi et al, 2004), suggesting a functional role in the photosynthetic activity during senescence or in the regulation of photoassimilate synthesis and/or partitioning between organs. PAs also inhibit ethylene biosynthesis and other degrative processes associated with senescence, including chlorophyll loss, increase in membrane leakage, and rise in RNAse and protease activities (Pandey et al, 2000).…”

Overexpression of apple spermidine synthase 1 (MdSPDS1) leads to significant salt tolerance in tomato plants

“…Kotzabasis et al (1993) reported that the main polyamines, putrescine, spermidine and spermine are associated with the thylakoid membranes and, especially, at the level of light-harvesting complex II as well as PSII complex. Several reports have attributed a key role of polyamines in the regulation of photosynthetic apparatus under adverse conditions like salinity and UV light (Demetriou et al 2007;Sfichi et al 2004). The EL reflects the damage of cell membranes.…”

Stress proteins and auxiliary anti stress compounds in intertidal macroalgae

“…A less known group of molecules called polyamines (PAs), which can be free in the cell or bound to thylakoid membranes of plants and algae, have been associated with repair or photoprotective functions during severe high light and UV stress (Sfichi-Duke et al, 2004), resembling functions of some stress proteins. The three major polyamines, putrescine (PUT), spermine (SPM) and spermidine (SPD) have been reported to have roles in many biological processes such as cell division, growth and senescence (Igarashi & Kashiwagi, 2000).…”