Potential of hydrogen (pH) differentially modulates cadmium stress response in abscisic acid-deficient sitiens tomato mutant

Georgia Bertoni Pompeu,Ricardo Antunes Azevedo,Simone Possedente De Lira,Rogério Falleiros Carvalho,Priscila Lupino Gratão,Milca Bartz Vilhena,Felipe Andrino,Guilherme Bovi Ambrosano

doi:10.1590/1678-4499.2018326

Georgia Bertoni Pompeu, Ricardo Antunes Azevedo + Show 6 more

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https://doi.org/10.1590/1678-4499.2018326

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Abstract

ABSTRACT Uptake of nutrients and cadmium (Cd) are dependent upon many factors, including plant species, ions concentration and pH. Tolerance to Cd-induced oxidative stress can be modulated by phytohormones such as abscisic acid (ABA), which induce the production of reactive oxygen species, activating proteins and enzymes involved in stress response and possibly stress tolerance. The present study aimed to evaluate the biochemical variations induced by Cd in ABA-deficient sitiens tomato mutant (sit) and its wild-type counterpart, Micro-Tom (MT), grown at different pH conditions. The plants were cultivated in nutrient solution (pH 5, 6 and 7; 20-days) and were then further grown over a 48-h period in 0 or 50 ?M CdCl2 at pH 6. Before Cd addition, the concentrations of nitrogen, sulfur, copper, iron and zinc were determined and variations in nutrients concentrations were observed. After Cd addition, sit roots grown at pH 5 and 7 did not exhibit differences in ascorbate peroxidase (APX) activity in 0 or 50 ?M CdCl2, and sit root grown at pH 6 exhibited lower glutathione reductase (GR) activity in the presence of Cd. Moreover, sit shoot grown at pH 5 showed decreased activities of superoxide dismutase (SOD), Mn-SOD II and Cu/Zn-SOD V, in 0 and 50 ?M CdCl2. The results indicated that pH modulates the plant nutrition in a complex way and may involve multiple ABA signaling pathways. Likewise, ABA status seems to be related with the Cd-translocation within the plant, suggesting that Cd, ABA and pH responses cannot be evaluated as isolated systems.

Highlights

Cadmium (Cd) is a heavy metal present in the environment in trace concentrations
The enzymatic mechanisms include the action of superoxide dismutase (SOD, EC 1.15.1.1) that catalyzes O2– into H2O2, which is subsequently detoxified into water (H2O) by catalase (CAT, EC 1.11.1.6) and ascorbate peroxidase (APX, EC 1.11.1.11) (Alves et al 2016; Noctor et al 2018)
Cd may induce a decrease in growth, reduction of photosynthesis, enzymatic and metabolic alterations, changes in stomata and electron transport (Mondal et al 2013), our results showed that plants of MT and sit exhibited increases in biomass production in the presence of Cd (Table 2)

Summary

Introduction

Cadmium (Cd) is a heavy metal present in the environment in trace concentrations. It can be introduced into the foodchain through anthropogenic activities such as wastewater usage for irrigation, sewage sludge application and fertilizers applications (Gratão et al 2005; Cuypers et al 2010; Borges et al 2018). The high mobility of Cd in the soil-plant system can affect biochemical mechanisms, causing plasma membrane rupture and serious disturbances in physiological processes such as photosynthesis, respiration, plantwater relations, uptake and distribution of macro- and micronutrients, plant growth reduction and/or even cell death (Gallego et al 2012; Moradi and Ehsanzadeh 2015; Alves et al 2017). Cd can increase the production of reactive oxygen species (ROS), resulting in extracellular superoxide anion radical (O2–) and hydrogen peroxide (H2O2) accumulation. The enzymatic mechanisms include the action of superoxide dismutase (SOD, EC 1.15.1.1) that catalyzes O2– into H2O2, which is subsequently detoxified into water (H2O) by catalase (CAT, EC 1.11.1.6) and ascorbate peroxidase (APX, EC 1.11.1.11) (Alves et al 2016; Noctor et al 2018)

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