Defensive strategies against high light stress in wild and D1 protein mutant biotypes of Erigeron canadensis

Abstract

The Ser264ÆGly substitution on the D1 protein is accompanied by a higher photosensitivity of the mutant plant. This may be due to an increased D1 protein turnover and/or to a lower xanthophyll cycle activity in vivo. The relative importance of these two photoprotective mechanisms in wild and D1 protein mutant biotypes of Erigeron canadensis L. was established by using dithiothreitol and streptomycin. Moreover, the interconversion of violaxan-thin to zeaxanthin via antheraxanthin was studied in isolated thylakoids and in intact leaves treated with paraquat. Streptomycin caused a more severe decrease in the optimal quantum yield (Fv/Fm) of PS II and a large increase in the initial fluorescence yield (Fo) in the mutant compared to the wild biotype. In the fluorescence-quenching parameters of the wild-type leaves, dithiothreitol caused alterations similar to those observed in the mutant plant without dithiothreitol. A lowered activity of the xanthophyll cycle was detected in the mutant biotype compared to the wild-type in vivo. However, under in vitro, conditions which were optimal for violaxanthin de-epoxidation, or when paraquat was used on intact leaves to accelerate the electron transport, violaxanthin could readily be converted to zeaxanthin even in the mutant plants. This demonstrates that neither the decrease in the enzymatic activity of violaxanthin de-epoxidase nor the low availability of violaxanthin is responsible for the low zeaxanthin formation under in vivo conditions. It is presumed that, in vivo, the D1 protein mutation results in slower electron transport, a smaller DpH and lower zeaxanthin formation, and thereby in alterations in the defensive strategies against high light illumination.

Parallel changes in non-photochemical quenching properties, photosynthesis and D1 levels at sudden, prolonged irradiance exposures in Ulva fasciata Delile

“…Previous investigations have shown that plants that are mutants in the D1 protein function, with a lower ability to maintain the proton motive force due to an impaired electron transport, have a lower ability of non-photochemical quenching [27,28]. These circumstances raised the question if the non-photochemical quenching properties in Ulva spp can be negatively affected at photoinhibitory conditions.…”

Conserved structure of the chloroplast-DNA encoded D1 protein is essential for effective photoprotection via non-photochemical thermal dissipation in higher plants

“…Gly (S264G) D1 protein mutation were found to have lower quantum yield of PSII (U PSII ), linear electron transport rate (ETR), light-induced photochemical quenching coefficient (qP), and they proved defective in non-photochemical quenching (NPQ) capacity as well as having an altered xanthophyll cycle pattern as compared with the wild-type plants (Curwiel and van Rensen 1996;Darkó et al 1996Darkó et al , 2000Sundby et al 1993;Váradi et al 1994Váradi et al , 2003. The highly conserved D1 protein is encoded by the psbA gene in the chloroplast-DNA (Morden and Golden 1989).…”

A D1 protein mutáció hatása a kettes fotokémiai rendszer energiahasznosítására eltérő vízellátású növényekben

“…Kimutatták továbbá, hogy az AR biotípusokban nagyobb sebességgel működik a D1 protein degradációs/helyreállítási folyamata (turn over) (Sundby et al, 1993a;Darkó et al, 2000). Elképzelhetőnek tartják, hogy a magasabb fényérzékenység a megemelkedett D1 protein turn over-nek (Sundby et al, 1993a) és/vagy in vivo a xantofill ciklus alacsonyabb aktivitásának (Váradi et al, 1994;Darkó et al, 1995) köszönhető.…”

“…folyamata az AR gyomokban (Sundby et al, 1993a;Darkó et al, 2000) maga után vonhat egy megnövekedett ATP igényt, ami az ATPáz enzimen keresztül magasabb proton effluxot eredményezhet, mely szintén hozzájárulhat a tilakoid membránon keresztüli proton gradiens kiépülésének csökkenéséhez. Ez magyarázatot adhat a 20%-kal alacsonyabb xantofill deepoxidációra, amely pedig hozzájárulhat a qE csökkenéséhez.…”

“…Az OJIP tranziensek kinetikáját a Q A redox állapotának változásai határozzák meg, de egyúttal a fotoszintetikus elektrontranszportlánc redukcióját is tükrözi. A tranziensek J és I szintjei és I-P fázisa a Q A redox állapotával, a PQ készlet redox állapotával és a PSI elektron akceptor oldalán lévő végső akceptorok redox állapotával függenek össze (Tsimilli-Michael & Strasser, 2008 (Darkó et al, 2000;Váradi et al, 2003). Azonban a Φ NPQ és a CO 2 asszimiláció fénytelítési sebességeinek hasonló értékeire a S. nigrum AS és AR vonalaiban ez nem ad magyarázatot (3.…”