Enhanced chloroplastic generation of H2O2 in stress-resistant Thellungiella salsuginea in comparison to Arabidopsis thaliana.
Bottom Line: In order to find some basis of salinity resistance in the chloroplastic metabolism, a halophytic Thellungiella salsuginea was compared with glycophytic Arabidopsis thaliana.Salinity treatment (0.15 and 0.30 M NaCl for A.t. and T.s., respectively) led to a decrease in ratios of chl a/b and F730 /F685 .In A.t., a salinity-driven enhancement of YII and NPQ was found, in association with the stimulation of H2 O2 production from PQ pool.
Affiliation: Department of Plant Physiology and Biochemistry, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, 30-387, Kraków, Poland.Show MeSH
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Mentions: To check the origin of H2O2 formation we use several inhibitors of PET. The typical runs from the electrode −/+ inhibitors are shown in Fig. S2. In the presence of DCMU, production of H2O2 by isolated thylakoids from control A.t. and T.s. plants was totally suppressed, indicating that this ROS formation undergo at the expense of electrons from PSII (Fig. 5A). To verify whether H2O2 production take place at PSI, electron transport was inhibited at the level of cyt b6f by the addition of DNP-INT. This compound inhibited gross of H2O2 production in Arabidopsis (90%) suggesting that Mehler reaction might be a major place of its formation. In contrast, the application of this compound slightly stimulated the H2O2 production in Thellungiella (by 21%). On this basis, we concluded that in T.s. H2O2 is formed predominantly at PQ pool. The addition of PTOX inhibitor OG (Josse et al. 2003) caused a significant stimulation of H2O2 formation (by 47%) in T.s. This result visualizes PTOX activity in the control T.s. plants and, at the same time, points to its protective function against ROS formation. On the other hand, a slight decrease in H2O2 formation (by 17%) caused by OG in A.t. in the absence of chlororespiration might be explained by a partial quenching of chlorophyll excitation, as this compound is the antioxidant and quencher of triplet states. If so, it is reasonable to assume that a partial quenching of PSII excitation by OG takes place also in T.s., hence a net contribution of chlororespiration would be slightly higher.
Affiliation: Department of Plant Physiology and Biochemistry, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, 30-387, Kraków, Poland.