Hydrogen peroxide produced by NADPH oxidases increases proline accumulation during salt or mannitol stress in Arabidopsis thaliana

Abstract

Summary Many plants accumulate proline, a compatible osmolyte, in response to various environmental stresses such as water deficit and salinity. In some stress responses, plants generate hydrogen peroxide (H2O2) that mediates numerous physiological and biochemical processes. The aim was to study the relationship between stress‐induced proline accumulation and H2O2 production. Using pharmacological and reverse genetic approaches in Arabidopsis thaliana, we investigated the role of NADPH oxidases, Respiratory burst oxidase homologues (Rboh), in the induction of proline accumulation was investigated in response to stress induced by either 200 mM NaCl or 400 mM mannitol. Stress from NaCl or mannitol resulted in a transient increase in H2O2 content accompanied by accumulation of proline. Dimethylthiourea, a scavenger of H2O2, and diphenylene iodonium (DPI), an inhibitor of H2O2 production by NADPH oxidase, were found to significantly inhibit proline accumulation in these stress conditions. DPI also reduced the expression level of Δ1‐pyrroline‐5‐carboxylate synthetase, the key enzyme involved in the biosynthesis of proline. Similarly, less proline accumulated in knockout mutants lacking either AtRbohD or AtRbohF than in wild‐type plants in response to the same stresses. Our data demonstrate that AtRbohs (A. thaliana Rbohs) contribute to H2O2 production in response to NaCl or mannitol stress to increase proline accumulation in this plant.

Proline coordination with fatty acid synthesis and redox metabolism of chloroplast and mitochondria

“…These data indicate how redox status, possibly including the redox status of the NADPH pool or ROS signaling, may be involved in adjusting Pro metabolism to match cellular redox and metabolic state. However, our result differs from that of Ben Rejeb et al (2015), who saw no effect of DPI on the Pro accumulation of unstressed plants. Their experiments were conducted on medium containing Suc, which could have altered metabolite levels and redox status and thus obscured the DPI Pro response.…”

“…However, a commonality is that both Pro and VLCFA synthesis consume NADPH and regenerate NADP + (Sharma et al, 2011;Li-Beisson et al, 2013;Giberti et al, 2014;Ben Rejeb et al, 2015) and, thus, can influence cellular Figure 4. Effects of cyp86a2 and lacs2 mutants on Pro metabolism and the identification of additional cuticle lipid-related mutants with increased Pro accumulation at low c w .…”

Alleviation of Drought Stress in <i>Arabidopsis thaliana</i> by 17<i>β</i>-Estradiol Application

“…Studies with Arabidopsis and rice plants showed that accumulation of proline, one of the most powerful osmoprotectant, was an essential response of the plant cells to drought stress [27] [28]. The beneficial drought-coping effect of ES treatment is evident from the observation that 10 and 100 nM ES-treated plants accumulated the highest levels of both GSH and proline when subjected to drought stress.…”

Proline Accumulation Is Regulated by Transcription Factors Associated with Phosphate Starvation

“…P5CS2 is considered to be a housekeeping gene with constitutive expression throughout the plant, while the stress-induced P5CS1 responds to hyperosmotic stress and is regulated by abscisic acid (ABA)-dependent and independent signals (Savouré et al, 1997;Strizhov et al, 1997;Székely et al, 2008;Sharma and Verslues, 2010). While P5CS2 can be activated by incompatible plant-pathogen interactions associated with hypersensitive response (Fabro et al, 2004), P5CS1 induction was shown to depend on light (Abrahám et al, 2003) and respond to ROS signals (Ben Rejeb et al, 2015). Besides ABA and light, calcium and lipid signals were implicated in regulation of P5CS genes and Pro biosynthesis (Thiery et al, 2004;Parre et al, 2007).…”

“…Furthermore, several reports describe Pro accumulation in response to other types of stress provoked by heavy metals (Schat et al, 1997;Jiang et al, 2012), oxidative agents (Yang et al, 2009;Ben Rejeb et al, 2015), or certain pathogens (Fabro et al, 2004;SenthilKumar and Mysore, 2012). Different protective functions were attributed to Pro, suggesting that it acts as osmoprotectant, stabilizing cellular structures and enzymes and scavenging reactive oxygen species (ROS), and maintains redox equilibrium in adverse conditions (Csonka, 1981;Hoque et al, 2008;Székely et al, 2008;Szabados and Savouré, 2010;Verslues and Sharma, 2010;Sharma et al, 2011;Zouari et al, 2016).…”