Gamma-aminobutyric acid (GABA) and acetylcholine (ACh) alleviate water deficit effects in soybean: From gene expression up to growth performance

• Published in: Environmental and experimental botany Vol. 182; p. 104303
• Main Authors: Braga-Reis, Inae, Neris, Daniel Moreira, Ribas, Alessandra Ferreira, Vieira, Luiz Gonzaga Esteves, Souza, Gustavo Maia
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.02.2021
• Subjects: Abiotic stress; acetylcholine; agricultural land; antioxidants; biomass production; Bioregulators; decline; drought; field capacity; gamma-aminobutyric acid; gene expression; genes; Glycine max; growth performance; leaves; photosynthesis; Priming; proline; seeds; soybeans; stomatal movement; synergism; water; Water deficit; water use efficiency; Priming; Abiotic stress; Glycine max; Water deficit; Bioregulators
• DOI: 10.1016/j.envexpbot.2020.104303
• ISSN: 0098-8472

•The application of ACh and GABA bioregulators in soybean promoted the better water-use efficiency (WUE) even under water déficit, hence contributing for a more stable CO2 assimilation with less water vapor molecule lost. Maintaining transpiration was in conjunction with greater Pn leading to significant improved WUE, due to the improvement of cell function. The physiological analysis suggested that ACh:GABA could alleviate drought damages in photosynthesis by balancing water relations through improving leaf water potential, WUE and osmotic adjustment.•The mitigation effects of ACh and GABA in soybean under water deficit was indirectly assessed by reducing the expression of P5CS1, LEA3 and ABA2 genes. However, we can not discard the possibility that the exogenous ACh application interferes in ABA biosynthesis pathway, resulting in a decrease in the expression levels of ABA2 and, therefore, lower levels of ABA content in the cells. The P5CS1 gene showed lower expression in plants that received application of the bioregulators, which resulted in lower proline accumulation in the leaves of plants, indicating that these plants were less stressed compared to control plants without application of ACh and GABA.•Soybean plants under water supplied with the ACh:GABA solution showed an increased antioxidant enzymes activity SOD, CAT e APX, indicating its protective role against the effects of ROS, along with a reduction in oxidative damage to the membranes of organelles and cells., suggesting that ACh:GABA has a role is a key adaptation of plants at the cellular level to minimize the effects of drought stress.•In plants treated with ACh:GABA showed remarkable responses on the growth and yield parameters.The improvement in the transport of photoassimilates, observed by the increase of photosynthetic efficiency in gas exchange analyses, resulted in better seed establishment, as observed in the production results. Grain yield was positively correlated to the net CO2 assimilation rate. Thus, the treatment with ACh: GABA priming was effective in mitigating production losses and reductions in net CO2 assimilation, under conditions of water deficit stress, through metabolic homeostasis. Thus, the bioregulators application in soybean has potential use in management practices in areas subject to water deficit. Bioregulators act as priming agents under abiotic stress conditions. Bioregulators such as gamma-aminobutyric acid (GABA) and acetylcholine (ACh) affect the efficiency of the antioxidant system and the regulation of the stomatal aperture, respectively. The aim of this study was to verify a possible synergistic effect among these bioregulators as attenuators of the effects of water deficiency in Glycine max. We combined the application of GABA and ACh at 2.0 mM in soybean plants under different water regimes. The factors studied were: 1) application of Gaba and ACh in seeds (S); in leaves (L); in seeds and leaves (SL); control without application (C); and (2) water regimes at 100 % field capacity (FC) and water deficit (WD). When the application of bioregulators were removed from the process, a severe decrease in photosynthesis capacity (93 %) was observed on the sixth day (after withholding water), as well as a higher expression of the genes known to be induced by water deficit. The combination of GABA and ACh applied to seeds and leaves under water deficit resulted in a lower decline in photosynthesis, as well as better water-use efficiency and biomass production. Soybean plants subjected to this treatment also showed lower expression of GmABA2, GmLEA3 and GmP5CS genes, lower proline content and increased activity of SOD, CAT and APX compared to the control treatment. The results indicate that the combined exogenous application of GABA and ACh in soybean plants acted to promote increased tolerance to water deficit, showing their potential for use on agricultural areas which are prone to droughts.