Oxidative and nitrosative‐based signaling and associated post‐translational modifications orchestrate the acclimation of citrus plants to salinity stress

Abstract

SUMMARYReactive oxygen and nitrogen species are involved in a plethora of cellular responses in plants; however, our knowledge on the outcomes of oxidative and nitrosative signaling is still unclear. To better understand how oxidative and nitrosative signals are integrated to regulate cellular adjustments to external conditions, local and systemic responses were investigated in the roots and leaves of sour orange plants (Citrus aurantium L.) after root treatment with hydrogen peroxide (H 2 O 2 ) or sodium nitroprusside (a nitric oxide donor), followed by NaCl stress for 8 days. Phenotypic and physiological data showed that pre-exposure to these treatments induced an acclimation to subsequent salinity stress that was accompanied by both local and systemic H 2 O 2 and nitric oxide (NO) accumulation. Combined histochemical and fluorescent probe approaches showed the existence of a vascular-driven long-distance reactive oxygen species and NO signaling pathway. Transcriptional analysis of genes diagnostic for H 2 O 2 and NO signaling just after treatments or after 8 days of salt stress revealed tissue-and time-specific mechanisms controlling internal H 2 O 2 and NO homeostasis. Furthermore, evidence is presented showing that protein carbonylation, nitration and S-nitrosylation are involved in acclimation to salinity stress. In addition, this work enabled characterization of potential carbonylated, nitrated and nitrosylated proteins with distinct or overlapping signatures. This work provides a framework to better understand the oxidative and nitrosative priming network in citrus plants subjected to salinity conditions.

Posttranslational Modifications of Chloroplast Proteins: An Emerging Field

“…in chloroplasts and mitochondria (Table I; LozanoJuste et al, 2011). In accordance with this finding, several photosynthesis-related proteins involved in the Calvin-Benson cycle were targeted by Tyr nitration in Citrus aurantium (Tanou et al, 2012; Fig. 1).…”

Role of Nitric Oxide in Salt Stress-induced Programmed Cell Death and Defense Mechanisms

“…Chloroplastic proteins such as oxygen-evolving enhancer protein 1 and 2,.small and large subunits of Rubisco, Rubisco activase, plastocyanin, and phosphoribulokinase are targets of S-nitrosylation in potato (Kato et al 2012). Photosynthesis-related proteins involved in the Calvin-Benson cycle were largely targeted by carbonylation, nitration, and nitrosylation in citrus plants primed with H2O2 or SNP prior to salt stress (Tanou et al 2012). The authors discussed the importance of these posttranslational modifications in the acclimation to high salinity.…”

“…13.2). NO accumulation was observed in roots (Xie et al 2008, Xu et al 2011a, leaves (Tanou et al 2012), calli (Zhao et al 2004(Zhao et al , 2007Vital Fig . 13.2 Changes in NO levels in the apical segments of tomato roots treated with 250 mM NaCl for 0 (a), 1 (b), 3 (c), and 6 (d) hours.…”

“…Protein nitration and 5-nitrosylation are also involved in acclimation to salinity stress (Valderrama et al 2007;Fares et al 2011;Tanou et al 2012). Tanou et al (2009) reported that some proteins undergo a post-translational regulation through either oxidation and/or 5-nitrosylation in citrus plants exposed to salinity.…”

“…Wu et al (2010) observed that in salt-stressed plants, the NO donor attenuated the decrease in stomatal conductance (g s ), transpiration rate (E), leaf chlorophyll content, net CO2 fixation rate (Pn), the ratio of variable to maximum fluorescence (Fv/Fm), relative electron transport rate (ETR), the effective quantum efficiency of photosys^ tern II (PS II) reaction centers (Fv'/Fm'), the photochemical quenching coefficient (qP), and counteracted the increase in non-photochemical quenching coefficient (qN) in tomato plants. SNP decreased the salt-induced loss of chlorophyll content in Arabidopsis thaliana (Zhang et al 2010), Brassica juncea (Khan et al 2012), Citrus aurantiwn (Tanou et al 2012), Triticum aestivum (Ruan et al 2002(Ruan et al , 2004a and Zea mays (Zhang et al 2006).…”