Protective Effect of γ-Aminobutyric Acid Against Chilling Stress During Reproductive Stage in Tomato Plants Through Modulation of Sugar Metabolism, Chloroplast Integrity, and Antioxidative Defense Systems

Abstract

Despite the role of γ-aminobutyric acid (GABA) in plant tolerance to chilling stress having been widely discussed in the seedling stage, very little information is clear regarding its implication in chilling tolerance during the reproductive stage of the plant. Here, we investigated the influence of GABA (1 and 2mM) as a foliar application on tomato plants (Solanum lycopersicum L. cv. Super Marmande) subjected to chilling stress (5°C for 6h/day) for 5 successive days during the flowering stage. The results indicated that applied GABA differentially influenced leaf pigment composition by decreasing the chlorophyll a/b ratio and increasing the anthocyanin relative to total chlorophyll. However, carotenoids were not affected in both GABA-treated and non-treated stressed plants. Root tissues significantly exhibited an increase in thermo-tolerance in GABA-treated plants. Furthermore, applied GABA substantially alleviated the chilling-induced oxidative damage by protecting cell membrane integrity and reducing malondialdehyde (MDA) and H2O2. This positive effect of GABA was associated with enhancing the activity of phenylalanine ammonia-lyase (PAL), catalase (CAT), superoxide dismutase (SOD), and ascorbate peroxidase (APX). Conversely, a downregulation of peroxidase (POX) and polyphenol oxidase (PPO) was observed under chilling stress which indicates its relevance in phenol metabolism. Interesting correlations were obtained between GABA-induced upregulation of sugar metabolism coinciding with altering secondary metabolism, activities of antioxidant enzymes, and maintaining the integrity of plastids’ ultrastructure Eventually, applied GABA especially at 2mM improved the fruit yield and could be recommended to mitigate the damage of chilling stress in tomato plants.

GABA in plants: developmental and stress resilience perspective

“…For instance, GABA application induced the expression and activities of antioxidant enzymes, including CAT, APX, SOD, and phenylalanine ammonia‐lyase (PAL) during chilling stress in wheat (Malekzadeh et al, 2012). Similar results were also reported in many other plants where the application of GABA causes a reduction in chilling‐induced oxidative damage by improving the cell membrane integrity and reducing MDA and H 2 O 2 (Abd Elbar et al, 2021). Moreover, GABA‐treated wheat plants exhibited a lesser impact of chilling stress due to improved biochemical and morphological parameters (Malekzadeh et al, 2012).…”

Folic Acid Reinforces Maize Tolerance to Sodic-Alkaline Stress through Modulation of Growth, Biochemical and Molecular Mechanisms

“…Several lines of evidence indicated that under abiotic-stress conditions, plants trigger a number of biochemical markers which function as signaling molecules to evolve the defensive mechanisms against this stress [3,60,61]. However, the excessive accumulation of these molecules, including reactive oxygen species (ROS) such as hydroxyl radicals (OH), alkoxy radicals (RO), superoxide anion radicals (O − 2 ), singlet oxygen (O 1 2 ), and hydrogen peroxide (H 2 O 2 ) can cause serious degeneration to various plant tissues and physiological processes [10,35,[62][63][64]. Furthermore, methylglycoxal (MG) as a reactive carbonyl species has been found to be toxic at high levels leading to the restriction of plant growth and development by affecting photosynthesis, stomatal movement, cytosolic calcium, root differentiation, and seed germination [25,65,66].…”

“…The cell-membrane stability index was estimated as described by Abd Elbar, et al [35]. Some leaf discs (8) were incubated for 24 h in 10 mL deionized water on a shaker.…”

Alpha Lipoic Acid as a Protective Mediator for Regulating the Defensive Responses of Wheat Plants against Sodic Alkaline Stress: Physiological, Biochemical and Molecular Aspects

“…Lipid peroxidation was quantified by measuring the peroxidation products, thiobarbituric acid reactive substances (TBARS). TBARS was quantified by the method of Abd Elbar et al [ 34 ] by reading the developed color at 535 nm and 600 nm. Hydrogen peroxide was quantified by the colorimetric method of potassium iodide as described by Velikova et al [ 35 ].…”