Responses of reactive oxygen species and methylglyoxal metabolisms to magnesium-deficiency differ greatly among the roots, upper and lower leaves of Citrus sinensis

Abstract

Background Magnesium (Mg)-deficiency is one of the most prevalent physiological disorders causing a reduction in Citrus yield and quality. ‘Xuegan’ ( Citrus sinensis ) seedlings were irrigated for 16 weeks with nutrient solution containing 2 mM (Mg-sufficiency) or 0 mM (Mg-deficiency) Mg(NO 3 ) 2 . Thereafter, we investigated the Mg-deficient effects on gas exchange and chlorophyll a fluorescence in the upper and lower leaves, and Mg, reactive oxygen species (ROS) and methylglyoxal (MG) metabolisms in the roots, lower and upper leaves. The specific objectives were to corroborate the hypothesis that the responses of ROS and MG metabolisms to Mg-deficiency were greater in the lower leaves than those in the upper leaves, and different between the leaves and roots. Results Mg level was higher in the Mg-deficient upper leaves than that in the Mg-deficient lower leaves. This might be responsible for the Mg-deficiency-induced larger alterations of all the measured parameters in the lower leaves than those in the upper leaves, but they showed similar change patterns between the Mg-deficient lower and upper leaves. Accordingly, Mg-deficiency increased greatly their differences between the lower and upper leaves. Most of parameters involved in ROS and MG metabolisms had similar variation trends and degrees between the Mg-deficient lower leaves and roots, but several parameters (namely glutathione S-transferase, sulfite reductase, ascorbate and dehydroascorbate) displayed the opposite variation trends. Obviously, differences existed in the Mg-deficiency-induced alterations of ROS and MG metabolisms between the lower leaves and roots. Although the activities of most antioxidant and sulfur metabolism-related enzymes and glyoxalase I and the level of reduced glutathione in the Mg-deficient leaves and roots and the level of ascorbate in the leaves were kept in higher levels, the levels of malonaldehyde and MG and/or electrolyte leakage were increased in the Mg-deficient lower and upper leaves and roots, especially in the Mg-deficient lower leaves and roots. Conclusions The ROS and MG detoxification systems as a whole did not provide sufficient detoxification capacity to prevent the Mg-deficiency-induced production and accumulation of ROS and MG, thus leading to lipid peroxidation and the loss of plasma membrane integrity, especially in the lower leaves and roots. Electronic supplementary material The online version of this article (10.1186/s12870-019-1683-4) contains supplementary material, which is available to authorized users.

Low pH effects on reactive oxygen species and methylglyoxal metabolisms in Citrus roots and leaves

“…ATP sulfurylase (ATPS), Cys synthase (CS), adenosine 5′-phosphosulphate (APS) reductase (APR), sulfite reductase (SiR), γ-glutamylcysteine synthetase (γGCS), Gly I and Gly II were extracted according to Cai et al [23]. ATPS, CS, Sir and APR activities were assayed according to Guo et al [29].…”

“…ATPS, CS, Sir and APR activities were assayed according to Guo et al [29]. γGCS was assayed as described previously [23]. Gly I and Gly II were assayed according to Guo et al [16].…”

“…Overproduction and accumulation of reactive oxygen species (ROS) and methylglyoxal (MG) in plant cells in response to abiotic stresses is a common phenomenon [16–20]. ROS are scavenged by diverse enzymatic and non-enzymatic detoxification systems [21–23]. Antioxidant enzyme (thiol-based antioxidant) system has been regarded as the first (second) line of defense against the oxidative stress [24].…”

Short-Term Magnesium Deficiency Triggers Nutrient Retranslocation in Arabidopsis thaliana

“…This results in surplus light energy, which provides reducing equivalents with molecular oxygen to form ROS. Meanwhile, recent studies suggest that sugar accumulation is not the only cause of ROS generation, as the oxidative damage is detected in leaves of Mgdeficient rice before sugars accumulate (Kobayashi et al, 2013b(Kobayashi et al, , 2018 and roots of Mg-deficient sweet orange (Cai et al, 2019). Apart from that, a decrease in leaf transpiration is reported in Mg-deficient rice (Kobayashi et al, 2013b) and maize (Jezek et al, 2015), and this is suggested to be responsible for chlorosis development (Kobayashi et al, 2013b).…”

Magnesium-Deficiency Effects on Pigments, Photosynthesis and Photosynthetic Electron Transport of Leaves, and Nutrients of Leaf Blades and Veins in Citrus sinensis Seedlings

“…Despite its vital roles in the normal growth and development of higher plants, less attention has been paid to Mg in comparison to nitrogen (N), phosphorus (P), and potassium (K) [6]. Mg-deficiency, one of the most common physiological disorder influencing productivity and quality of crops including Citrus , is being intensified in intensive agricultural systems, where N, P, and K fertilizers have been heavily applied [7,8,9,10,11].…”