Enhanced chloroplastic generation of H₂O₂ in stress‐resistant Thellungiella salsuginea in comparison to Arabidopsis thaliana

Abstract

In order to find some basis of salinity resistance in the chloroplastic metabolism, a halophytic Thellungiella salsuginea was compared with glycophytic Arabidopsis thaliana. In control T.s. plants the increased ratios of chlorophyll a/b and of fluorescence emission at 77 K (F730/F685) were documented, in comparison to A.t.. This was accompanied by a higher YII and lower NPQ (non-photochemical quenching) values, and by a more active PSI (photosystem I). Another prominent feature of the photosynthetic electron transport (PET) in T.s. was the intensive production of H2O2 from PQ (plastoquinone) pool. 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 H2O2 production from PQ pool. In contrast, in salinity-treated T.s., these variables were similar as in controls. The intensive H2O2 generation was accompanied by a high activity of PTOX (plastid terminal oxidase), whilst inhibition of this enzyme led to an increased H2O2 formation. It is hypothesized, that the intensive H2O2 generation from PQ pool might be an important element of stress preparedness in Thellungiella plants. In control T.s. plants, a higher activation state of carboxylase ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco, EC 4.1.1.39) was also documented in concert with the attachment of Rubisco activase (RCA) to the thylakoid membranes. It is supposed, that a closer contact of RCA with PSI in T.s. enables a more efficient Rubisco activation than in A.t.

Adaptations of Chloroplastic Metabolism in Halophytic Plants

“…Our recent data point to a much higher generation of H 2 O 2 by PET in T. halophila in comparison to A. thaliana (Wiciarz et al 2014). Similarly, in leaves of S. salsa the level of H 2 O 2 was found to be lower after salinity than in control conditions .…”

“…Despite that, Rubisco appeared to be more highly activated in vitro (Davies and Griffiths 2012). Our recent study made on T. halophila revealed that a majority of RCA is attached to the thylakoid membranes, in contrast to A. thaliana where the soluble form is predominant (Wiciarz et al 2014). This is associated by a higher Rubisco activation state in the former species.…”

“…In agreement with this view, in salinity-treated A. thaliana increased NPQ was associated with a more oxidized P700 under a steady-state photosynthesis, while in salinity-treated T. halophila the value of NPQ stayed low and P700 stayed reduced (Stepien and Johnson 2009). Intriguingly, in T. halophila an indication of stt was found in controls, but not after salinity treatment, as shown by changes in a 77K chlorophyll emission spectra (Wiciarz et al 2014). Because a reduced PQ pool promotes stt (Tikkanen and Aro 2012), a less reduced PQ pool might be expected after salinity treatment than in controls.…”

The Chlamydomonas alternative oxidase 1 is regulated by cadmium stress: New insights into control of expression

“…3). There are different possibilities for the generation of H 2 O 2 within plant cells under different conditions (Wiciarz et al, 2015). To our data, under Cd stress illuminated cells produce higher levels of H 2 O 2 than dark-adapted cells (Fig.…”

Acclimation of the photosynthetic apparatus and alterations in sugar metabolism in response to inoculation with endophytic fungi

“…The thylakoids were isolated as described by Wiciarz, Gubernator, Kruk, and Niewiadomska (2015), and their activity was measured as the rate of oxygen evolution/consumption using a Clark-type oxygen electrode (Oxytherm, Hansatech, UK). The total electron transport activity was tested by applying 1 mM K 3 [Fe (CN) 6 ] as the electron acceptor, whereas the PSII activity was measured using 0.1-mM 2,6dichloro-1,4-benzoquinone.…”