Abstract
Metalloid contamination, such as arsenic poisoning, poses a significant environmental problem, reducing plant productivity and putting human health at risk. Phytohormones are known to regulate arsenic stress; however, the function of strigolactones (SLs) in arsenic stress tolerance in rice is rarely investigated. Here, we investigated shoot responses of wild-type (WT) and SL-deficient d10 and d17 rice mutants under arsenate stress to elucidate SLs’ roles in rice adaptation to arsenic. Under arsenate stress, the d10 and d17 mutants displayed severe growth abnormalities, including phenotypic aberrations, chlorosis and biomass loss, relative to WT. Arsenate stress activated the SL-biosynthetic pathway by enhancing the expression of SL-biosynthetic genes D10 and D17 in WT shoots. No differences in arsenic levels between WT and SL-biosynthetic mutants were found from Inductively Coupled Plasma-Mass Spectrometry analysis, demonstrating that the greater growth defects of mutant plants did not result from accumulated arsenic in shoots. The d10 and d17 plants had higher levels of reactive oxygen species, water loss, electrolyte leakage and membrane damage but lower activities of superoxide dismutase, ascorbate peroxidase, glutathione peroxidase and glutathione S-transferase than did the WT, implying that arsenate caused substantial oxidative stress in the SL mutants. Furthermore, WT plants had higher glutathione (GSH) contents and transcript levels of OsGSH1, OsGSH2, OsPCS1 and OsABCC1 in their shoots, indicating an upregulation of GSH-assisted arsenic sequestration into vacuoles. We conclude that arsenate stress activated SL biosynthesis, which led to enhanced arsenate tolerance through the stimulation of cellular antioxidant defense systems and vacuolar sequestration of arsenic, suggesting a novel role for SLs in rice adaptation to arsenic stress. Our findings have significant implications in the development of arsenic-resistant rice varieties for safe and sustainable rice production in arsenic-polluted soils.
Highlights
MethodsRice seeds were sterilized with sodium hypochlorite, allowed for germination in an incubator under dark conditions at 28 ± 2 ◦ C [33,34]
Plant growth and developmental processes are regulated by several endogenous
We have investigated arsenic-metal homeostasis, oxidative stress induction, antioxidant defense response, mineral balance and vacuolar sequestration of arsenic to understand the mechanistic aspects of SL-mediated AsV tolerance in rice shoots
Summary
Rice seeds were sterilized with sodium hypochlorite, allowed for germination in an incubator under dark conditions at 28 ± 2 ◦ C [33,34]. Fourteen-day-old WT and SL mutant plants were subjected to three levels of sodium arsenate (Na2 AsO4 , AsV ) (0, 125 and 250 μM, hereafter referred to as As0, As1 and As2) in the nutrient solution to evaluate the effect of AsV stress. Following their exposure to AsV treatments, rice plants were allowed to grow for an extra five days in the above-mentioned conditions. Each treatment was replicated thrice under the identical experimental circumstances
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