Overexpression of 2-Cys Prx Increased Salt Tolerance of Photosystem II in Tobacco

Abstract

To explore the plant active oxygen scavenging and photosynthesis function of 2-Cys Prx, a newly discovered member of the antioxidant protease family, the tobacco 2-Cys Prx gene was cloned into the plant expression vector prok II. This vector, which is controlled by the constitutive strong promoter CaMV35S, was introduced into tobacco by Agrobacteria-mediated transformation. The 816-bp open reading frame of tobacco 2-Cys Prx encodes 271 amino acids and showed high homology with 2-Cys Prx genes from Solanum lycopersicum, Vitis vinifera, and Populus trichocarpa, indicating 2-Cys Prx gene is highly conserved. The active oxygen metabolism and chlorophyll fluorescence response to salt stress were also studied. Under salt stress, superoxide dismutase (SOD) activity in tobacco leaves increased, while ascorbate peroxidase (APX) activity decreased. Additionally, the donor-and acceptor-side function of photosystem II (PSII) were affected by salt stress to different degrees, with the latter significantly more affected than the former. The H2O2 and malondialdehyde content of 2-Cys Prx-overexpression tobacco leaves under salt stress were all significantly lower than those of wild-type (CK) leaves. The PSII maximum photochemical efficiency (Fv/Fm) and the performance index on absorption basis (PIABS) of 2-Cys Prx-overexpression leaves were significantly lower than those of CK leaves under salt stress. Various relative fluorescence intensities of the 2-Cys Prxoverexpression plants exhibited significantly lower increases in amplitude than those of CK plants. Thus, 2-Cys Prx increased the salt tolerance of PSII function and lowered the PSII light inhibition effect in plants under salt stress, suggesting that 2-Cys Prx gene overexpression can alleviate H2O2 buildup and lower the peroxide levels of cytomembrane lipids under salt stress. Thus, 2-Cys Prx gene overexpression can protect oxygen-evolving complex function at the donor side of PSII under salt stress and improve electron transfer at the acceptor side of PSII.

Effects of four types of sodium salt stress on plant growth and photosynthetic apparatus in sorghum leaves

“…The effects of different types of sodium salt stress on the PQ pool of the sorghum leaves were not significant, and the differences among different types of sodium salt treatments were small. The differences among different types of sodium salt stress were not significant for V I , there were some increases in the relative variable fluorescence V K at 0.3 ms point K. The increase in V K is considered to be a specific sign of damage to the oxygen-evolving complex (OEC) on the electron donor side of PSII (Zhang et al 2017). These results indicated that the OEC was affected by different types of sodium salt stress, but the sensitivities showed no significant differences under the stresses of alkaline salts from that of neutral salts.…”

Exogenous melatonin improves salt tolerance in tomato by regulating photosynthetic electron flux and the ascorbate–glutathione cycle

“…The increase of the relative variable fluorescence V k at the K point (300 μs) was due to the inhibition of the water-splitting system and the partial suppression of the acceptor side before Q A (Figure 3(D,E)). The K step of the chlorophyll a fluorescence transient (quantified as V K ) is an indicator of OEC injury in the photosynthetic apparatus (Strasser 1997;Zhang et al 2017). The K phase was clearly visible in the standardized O-J curve (Figure 3(D,E)), and V K also increased significantly under NaCl stress (Figure 3 (D,E)).…”

“…The K phase was clearly visible in the standardized O-J curve (Figure 3(D,E)), and V K also increased significantly under NaCl stress (Figure 3 (D,E)). The increase in V K is considered to be a sign of damage to the oxygen-evolving complex (OEC) on the electron donor side of PSII (Zhang et al 2017). However, the increase in V K was reduced when exogenous MT was applied (Figure 3(D,E)).…”

Special issue in honour of Prof. Reto J. Strasser - Effects of exogenous abscisic acid on the photosynthetic function and reactive oxygen species metabolism of tobacco leaves under drought stress

“…Under adverse conditions, plant photosynthetic electron transport is often blocked on the electron donor and acceptor sides of the PSII reaction center; the transfer of QA to QB is the main inhibitory site (Zhang et al 2019b). The increase in the relative variable fluorescence VJ at point J (2 ms) on the normalized O-P curve indicated that the electron transfer from QA to QB in the photosynthetic electron transport chain was blocked (Zhang et al 2017(Zhang et al , 2018c. The increase in the relative variable fluorescence VK at point K (0.3 ms) on the normalized O-J curve was considered a specific marker of the damage to the activity of oxygen-evolving complex on the PSII electron donor side (Zhang et al 2012(Zhang et al , 2016.…”