Ponceau S Staining Solution Nitrosylation mediated post tra

Nitrosylation-mediated post-translational modifications of proteins through GSNOR play critical roles in modulating plant defense responses to diverse abiotic and biotic stresses (Frungillo et al., 2013, Leterrier 2011). As the most fundamental and intricate physiological process of plants, photosynthesis is often severely affected by Fe-deficiency stress (Graziano et al., 2002). The synthesis of chloroplastic proteins and chlorophyll is tightly connected with the complete development of chloroplasts (Graziano et al., 2002). In this sense, Fe deficiency is associated with cytological alterations that affect the chloroplastic ultrastructures (Fig. 2C). In this study, chloroplasts of young leaves were severely altered by Fe-deficiency stress. With disordered chloroplasts, the photosynthesis and the accumulation of starch was affected. Therefore, the starch granules are disappearing with time. Chloroplasts from Fe-deficient WT lines failed to develop normal grana stacking (Fig. 2C). In contrast, chloroplasts from mesophyll Ponceau S Staining Solution of transgenic plants developed grana that were also disordered but not as severely as under Fe-deficiency conditions (Fig. 2C). / has been used to evaluate, rapidly and noninvasively, the operating quantum efficiency of electron transport through PSII in plants, and its decrease is a reliable sign of photoinhibition. In the present study, much greater chlorophyll contents in GSNOR-OE lines were observed under Fe-deficiency conditions, and this may be partly responsible for the observed greater Pn, /, , and values and the lower NPQ value in the transgenic lines (Table 1). The greater / and values in transgenic lines indicated that the ability of PSII to reduce the primary acceptor QA was increased by the overexpression of GSNOR. Greater value in transgenic lines under Fe-deficiency stress also revealed that the overexpression of GSNOR increased the distribution of light energy during plant growth compared with in the WT lines. In the present experiment, the overexpression of GSNOR reversed, to a great extent, the damage to the chloroplastic ultrastructure and membrane system induced by Fe deficiency, resulting in a greater photosynthetic capacity under Fe-deficiency stress. Several proteins of the photosynthetic process, including Rubisco large chain, Rubisco small chain, PSII P680 47-kD protein, PSII D2 protein, and PSII oxygen-evolving complex, can be S-nitrosylated by NO and SNOs in plant cells (Lindermayr et al., 2005). In addition to the key enzymes of the Calvin cycle, proteins of PSII in particular seemed to be targets for NO and SNOs. Proteins of the PSII reaction center, including D1, D2, and some subunits of PSII, were stimulated by moderately thiol-reducing conditions and maintained at high levels under highly reducing conditions (Carlberg et al., 1999). Furthermore, the reversible inhibition of photophosphorylation by NO as well as SNOs has been demonstrated (Takahashi and Yamasaki, 2002), suggesting that proteins of the energy transduction system in both thylakoids and chloroplasts could be affected by S-nitrosylation. This study provided new evidence that the overexpression of GSNOR degraded intracellular RNS to reduce the surplus S-nitrosylation of photosynthetic proteins, which protected the photosynthetic apparatus against Fe-deficiency stress. O2·− and H2O2 levels are well-known indices for determining the degree of oxidative stress and are considered to be important contributors to growth retardation under detrimental conditions. The overexpression of GSNOR could protect cell membrane systems from oxidative damage under Fe-deficiency stress (Fig. 3A, B). A greater GSNOR activity level results in a lower NO concentration (Ziogas et al., 2013), which increases the tolerance to abiotic stress by preventing the accumulation of ROS. Additionally, the GSNOR mutant lines significantly increased the ROS accumulation, showing that decreasing the endogenous RNS biosynthesis is an effective strategy for enhancing crop tolerance to abiotic stress (Chen et al., 2009, Yun 2011). Like previous reports, greater activities of ROS-detoxifying enzymes were observed in the transgenic tomato lines compared with in WT plants.