Modeling and optimizing concentration of exogenous application of γ-aminobutyric acid on NaCl-stressed pineapple mint (Mentha suaveolens) using response surface methodology: an investigation into secondary metabolites and physiological parameters

Abstract

Salinity, a severe worldwide issue, compromises the economic production of medicinal plants including mints and causes drug-yield decline. γ-Aminobutyric acid (GABA) is a tolerance-inducing signaling bio-molecule in various plant physiological processes. Pineapple mint (Mentha suaveolens Ehrh.) is a valuable medicinal herb with an exhilarating scent of citrus fruit. Piperitenone oxide is the major bioactive constituent of its essential oil, having significant demand by pharmaceutical industries. Nonetheless, modeling and optimizing the effective concentration of GABA remain within twin foci of interest. Therefore, a two factor-five level (NaCl 0-150 mM and GABA 0-2.4 mM) central composite design was conducted to model and optimize drug yield and physiological responses of M. suaveolens. Based on the design of experiments (DoE) approach, different linear, quadratic, cubic, and quartic models were assigned to the response variables. Change trends of shoot and root dry weights followed a simple linear model, whereas sophisticated models (i.e., multiple polynomial regression) were fitted to the other traits. NaCl stress inevitably reduced root and shoot dry weight, piperitenone oxide content, relative water content, pigments content, and maximum quantum yield of PSII. However, content of malondialdehyde (MDA) and total flavonoid, and DPPH radical scavenging activity were increased under salinity. Under severe NaCl stress (150 mM), the essential oil content (0.53%) was increased three times in comparison with control (0.18%). Optimization analysis demonstrated that the highest amount of essential oil (0.6%) and piperitenone oxide (81%) as a drug yield-determining component would be achievable by application of 0.1–0.2 mM GABA under 100 mM NaCl. The highest dry weight of root and shoot was predicted to be achieved at 2.4 mM GABA. Overall, extremely severe NaCl stress (i.e., more than 100 mM) in which a sharp drop in yield components value was observed seemed to be out of M. suaveolens salinity tolerance range. Hence, it is rationale to compensate the decrease of drug yield by foliar application of a dilute GABA solution (i.e., 0.1–0.2 mM) under 100 mM NaCl stress or lower levels.

RNA-seq analysis reveals narrow differential gene expression in MEP and MVA pathways responsible for phytochemical divergence in extreme genotypes of Thymus daenensis Celak

“…Following the optimized method for quantification of EOs in our previous studies [ 40 – 41 , 57 ], GC-MS (Agilent 5977 A) and GC-FID (Agilent 7990B) analysis of 24 samples (4 phenological stage × 2 genotype × 3 rep) was performed utilizing an HP-5MS capillary column (5% phenylmethyl polysiloxane, 30 m length, 0.25 mm internal diameter, 0.1 μm film thickness). EO samples were diluted with n -hexane (1:100), after which an aliquot of 1 µL was injected.…”

“…Moreover, the identity of some constituents was reconfirmed by peak assignment of certified reference standards (thymol, carvacrol, caryophyllene oxide, carvacrol methyl ether, and γ-terpinene, Supleco, USA). The content of each EO compound was expressed as relative percentage of that constituent [ 57 ].…”

Integrating transcriptome and metabolome to explore the growth-promoting mechanisms of GABA in blueberry plantlets

“…A large number of studies have shown that when plants are subjected to stresses (both abiotic and biotic) such as hypoxia, drought, cold, heat, salt, ultraviolet, heavy metals, mechanical damage, and diseases and pests, GABA can rapidly accumulate to maintain the equilibrium of redox, cytoplasmic pH, osmotic potential, and C/N content in the cells to ensure their normal physiological metabolism under adverse conditions and alleviate the extent of damage caused by these stresses (Seifikalhor et al, 2019;Li et al, 2020;Abd Elbar et al, 2021;Mishra et al, 2023;Ullah et al, 2023). The exogenous application of GABA can improve the stress resistance of plants and promote their growth under stress by increasing stomatal conductance, improving the activities of antioxidant enzymes, promoting the production of stress-response amino acids and polyamines, and regulating the metabolism of organic acids among others (Jin et al, 2019;Wang et al, 2022;Ahmadi et al, 2023). Although numerous studies have identified the contribution of GABA to plant growth and development under different stress conditions and the underlying mechanisms of GABA actions, the effects of exogenous GABA on the growth of the in vitro plantlets under the extreme artificial conditions of tissue culture and the related molecular mechanisms remain unclear.…”