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 measurements 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 on the photosynthetic apparatus. The separation of oligomeric and monomeric forms 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, whereas 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.

Response of transglutaminase activity and bound putrescine to changes in light intensity under natural or controlled conditions in Quercus ilex leaves

“…On the basis of our data for chlorophyll fluorescence parameters, the highest TGase activity and B‐Put content coincided with the period of the highest photoprotective need. It has been reported that the ratio Put/Spd in thylakoids is related to the status of the photosynthetic apparatus (Logothetis et al 2004, Sfakianaki et al 2006, Sfichi et al 2004). In the forest, the increase in the B‐Put/B‐Spd ratio from morning to midday and its decrease in the evening to about the initial values indicate photoadaptation of the photosynthetic apparatus to the highest PPFD at midday.…”

“…Moreover, PAs, especially those bound to thylakoid membranes, have been reported to protect the photosynthetic apparatus in colonial green algae by regulating the size of the PSII light‐harvesting complex (LHCII) during stress such as ozone pollution (Navakoudis et al 2003), elevated CO 2 treatment (Logothetis et al 2004) and UV‐B radiation (Sfichi et al 2004). PAs are also synthesized and oxidized in chloroplasts (Kotzabasis et al 1993), and the addition of PAs inhibits the destruction of thylakoids and prevents loss of pigment during senescence (Besford et al 1993).…”

Polyamines in macroalgae: advances and future perspectives

“…A study by Sfichi et al. () showed thylakoid‐associated PUT levels decreased after exposure to UV‐B, while SPM increased, in the unicellular alga Scenedesmus obliquus . As a consequence the ratio of PUT:SPM was reduced and the LHCII gained in size, taking up more space in the reaction center and therefore intensifying the effects of UV‐B radiation.…”

“…, Sfichi et al. , Sfichi‐Duke et al. ), thus influencing the size of the LHCII through the processes of binding or detaching (Ioannidis et al.…”

Chemical Bonding of Chlorophylls and Plant Aminic Axial Ligands Impact Harvesting of Visible Light and Quenching of Fluorescence

“…Furthermore, in isolated reaction centers of PSII was found specifically mainly the tetramine Spm (22). The in vivo significance of the role of plastidal polyamines, might be high in photosynthesis based in: (1) in vitro data that show 70% stimulation of the photophosphorylation by massive uptake of Put (14); (2) the important photoprotection of green algae due to high Put (23,24); (3) Spm protect PSII from photoinhibition (25); and (4) a three‐ to six‐fold increase of energization quenching (qE) by artificial elevation of plastidal polyamines and overexpression of the plastidal transglutaminase in higher plants respectively (15,26). The exact molecular mechanism of qE, which is a key process for plant growth, productivity and tolerance is currently under debate (27–31) and thus, any report that could increase our understanding regarding the modulation of Chl fluorescence is of exceptional importance.…”