Beneficial role of acetylcholine in chlorophyll metabolism and photosynthetic gas exchange in Nicotiana benthamiana seedlings under salinity stress

Abstract

Acetylcholine (ACh) is believed to improve plant growth. However, regulation at biochemical and molecular levels is largely unknown.• The present study investigated the impact of exogenously applied ACh (10 µM) on growth and chlorophyll metabolism in hydroponically grown Nicotiana benthamiana under salt stress (150 mM NaCl).• Salinity reduced root hydraulic conductivity while ACh-treated seedlings exhibited a significant increase, resulting in increased relative water content. Salinity induced a reduction in chlorophyll biosynthetic intermediates, such as protoporphyrin-IX, Mgphotoporphyrin-IX and protochlorophyllide, which were significantly ameliorated in the presence of ACh. This influence of ACh on chlorophyll synthesis was confirmed by up-regulation of HEMA1, CHLH, CAO and POR genes. Gas exchange parameters, i.e. stomatal conductance, internal CO 2 concentration and transpiration rate, increased with ACh, thereby alleviating the salinity effects on photosynthesis. In addition, the salinity-induced enhancement of lipid peroxidation declined after ACh treatment through modulation of the activity of the assayed antioxidant enzymes (superoxide dismutase and peroxidase). Importantly, ACh significantly reduced the uptake of Na and increased uptake of K, resulting in a decline in the Na/K ratio.• Results of the present study indicate that ACh can be effective in ameliorating NaClinduced osmotic stress, altering chlorophyll metabolism and thus photosynthesis by maintaining ion homeostasis, hydraulic conductivity and water balance.

Exogenous Myo-Inositol Alleviates Salt Stress by Enhancing Antioxidants and Membrane Stability via the Upregulation of Stress Responsive Genes in Chenopodium quinoa L.

“…In the same way, Pn, gs, E, and PSII activity was enhanced due to MYO exogenous application and amendment of the saline regime. Similarly to our results, a decline in chlorophyll content, Pn, gs, E, and PSII activity has been reported in different plants [7,[75][76][77]. In salt-stressed Dianthus caryophyllus, Kwon et al [74] demonstrated a decline in Pn, gs, E, intercellular CO 2 , and stomata cavity in the lower and upper epidermis, with a significant decrease in their size and density.…”

Metabolomics and Physiological Insights into the Ability of Exogenously Applied Chlorogenic Acid and Hesperidin to Modulate Salt Stress in Lettuce Distinctively

“…In this regard, when plants are subjected to salinity, stomatal guard cells limit stomatal conductance to reduce the transpiration rate, consequently impairing the photosynthesis and gas exchange parameters [33] (Figure 2). Indeed, the photosynthesis system is reported as one of the first physiological processes affected by saline stress, and Qin et al [8] reported a direct correlation between the amelioration of gas exchange parameters, affected by salinity, and the recovery of photosynthesis activity, after the exogenous application of acetylcholine (ACh). The authors confirmed that salt stress produced a reduction in chlorophyll biosynthetic intermediates, i.e., protoporphyrin-IX, Mg-photoporphyrin-IX, and protochlorophyllide, which were significantly enhanced in the presence of ACh.…”

“…Indeed, some authors reported that the regulation of chlorophyll biosynthesis in plants depends on the type of stress applied, producing important consequences on the growth and reduction of biomass [5][6][7]. To overcome salinity-mediated growth reduction, plants activate tolerance mechanisms such as antioxidant systems, osmolyte accumulation, and the compartmentalization of toxic ions [8]. Many studies have previously shown that the production and accumulation of reactive oxygen species (ROS) such as superoxide (O 2 − ), hydrogen peroxide (H 2 O 2 ), and singlet oxygen are parallel with exposure time and density in plants exposed to salt stress.…”

Sulfamethoxazole-Altered Transcriptomein Green Alga Raphidocelis subcapitata Suggests Inhibition of Translation and DNA Damage Repair

“…The reduction of PChlide is considered to be the rate-limiting step of the chlorophyll branch and as the rate of Chl protein synthesis depends strictly on Chl availability. Moreover, the shortage and excess of por enzyme activity will have a fatal effect on cell activity ( Qin et al, 2020 ). Other pigments such as chlorophyll b and carotenoids absorb light energy and transfer to chlorophyll a ( Rai et al, 2014 ).…”