SAR405 sale Of what interest is the
Of what interest is the link between GSNOR and NO in the plant response to Fe deficiency? On the one hand, NO acts as an important signal to help plants accommodate Fe deficiencies; on the other hand, surplus NO is indeed a harmful RNS that induces severe S-nitrosylation-related damage at a higher subcellular level. To study GSNOR, as well as its regulated NO homeostasis, in plant responses to Fe deficiency, transgenic tomato plants transformed with a sense construct of the GSNOR gene, under the control of the 35S cauliflower mosaic virus promoter, were developed. Our results demonstrated that the overexpression of GSNOR decreased the detrimental effects of Fe deficiency in tomato plants by impacting Fe metabolism and redox homeostasis.
Materials and methods
Discussion GSNOR has been intensively studied in plants undergoing SAR405 sale to unfavorable stresses and fruit ripening (Leterrier et al., 2011; Rodríguez-Ruiz et al., 2017). However, GSNOR’s function as an important regulator involved in the NO pathway under stress conditions has only been hypothesized in plants (Cheng et al., 2017; Kubienová et al., 2014). To date, there is very little experimental evidence of the molecular mechanism of GSNOR in Fe metabolism at the genetic level. In the present study, changes in GSNOR’s expression profile in tomato plants responding to Fe deficiency stress led us to hypothesize that GSNOR was related to Fe-deficiency tolerance. NO and other RNS molecules are important in many plant physiological processes, and NO acts either as a signal or a toxic molecule depending on its level in a plant cell (Hasanuzzaman et al., 2018; Zhang et al., 2017a). In the present study, the intracellular NO and SNO contents were inversely correlated with the activity levels of GSNOR in WT and transgenic lines under Fe-deficiency conditions (Fig. 4), which indicated that the overexpression of GSNOR mitigated the surplus RNS injury caused by the Fe deficiency. Thus, the GSNOR enzyme appears to have an important role in the maintenance of NO homeostasis and the regulation of intracellular SNO levels in plants exposed to stress conditions. Moreover, intracellular GSNO levels, regulated by GSNOR, have been proposed to influence the total NO and SNO contents, likely through the transnitrosylation reactions of protein Cys residues (Frungillo et al., 2013). The present results provide further evidence of the importance of GSNOR in the regulation of NO (Fig. 4B, D, E) homeostasis and the maintenance of endogenous SNO (Fig. 4C) levels in plant cells. In the present study, the levels of GSNOR activity in WT lines were induced by the Fe-deficiency treatment, and significantly greater NO concentrations were also shown in stressed tomato plants (Fig. 4), implying that GSNOR might act as an early regulator of Fe-deficiency stress through the NO pathway. A long-term Fe deficiency led to a sharp rise in the intracellular SNO contents (Fig. 4C), despite the decrease in the GSNOR activity (Fig. 4A) caused by the Fe-deficiency treatment, which was accompanied by an increase in NO emissions in both WT and transgenic lines. However, the NO (Fig. 4B) and SNO (Fig. 4C) contents for each line were positively correlated with the corresponding intracellular O2·– (Fig. 3A) and H2O2 (Fig. 3B) accumulation levels. Under Fe-deficiency conditions, the WT lines had the greatest NO and SNO contents, while the levels were lowest in the OE-2 line, having patterns similar to the ROS accumulation (Fig. 3, Fig. 4). This complex response to Fe-deficiency stress may result from the indirect involvement of GSNOR in the modulation of the cell redox state, except for GSNOR’s role in GSNO degradation (Leterrier et al., 2011). Therefore, we considered that the role of GSNOR in regulating NO signals is complicated. GSNOR’s activity decreased in OE lines to produce NO signals under earlier Fe-deficiency conditions but increased to scavenge excess RNS under middle Fe-deficiency conditions. Under later Fe-deficiency conditions, accompanied by dysfunction, the activity level of GSNOR decreased. This sensitive feedback mechanism might be dependent on abundant S-nitrosylation sites in the GSNOR protein sequence, and this was analyzed by GPS-SNO software (Supplemental Table 2; Xue et al., 2010). In addition, the long-term Fe deficiency led to the accumulation of excess NO and SNO, which allows the protein S-nitrosylation mechanism to decrease the RNS burst. Complementarily, the overexpression of GSNOR decreased the accumulation of excessive RNS in tomato plants (Gong et al., 2015).