Exogenous γ-aminobutyric acid enhanced salt-alkaline tolerance in mulberry trees through transcriptomic sequencing analysis

• Salt and alkali stress of mulberry could be alleviated by soaking seeds with 0.5 mM GABA. • GABA mitigated saline-alkaline stress by regulating the development and growth of adventitious roots of mulberry trees and enhancing the immunity of root cells. • Five enriched pathways involved in signal transduction in plant cells were regulated by GABA. • Transcriptomics showed that GABA mainly regulated a series of genes related to cell wall synthesis and modification such as MYB, PME, SBT, EXP, DIR, POD to adjust the ductility and hardness of the cell wall of mulberry tree roots under saline-alkali stress. Soil salinization is a widespread abiotic stress in China and one of the most critical factors affecting agricultural production and food security. γ-Aminobutyric acid (GABA) is a non-protein amino acid widely found in vertebrates, plants, and microorganisms, regulating the nervous system as well as plant defense systems. Mulberry is rich in GABA and exhibits extensive adaptability to various environments. In this study, we explored the possibility of alleviating salinity and alkalinity stress in mulberry seedlings using GABA and elucidating the intrinsic mechanisms by which GABA enhances salt-alkaline tolerance in mulberry trees through transcriptomic sequencing analysis. The results showed that 1 mM exogenous GABA enhanced the activities of mulberry seeds under saline-alkali stress, significantly increased the activities of POD and CAT ( P < 0.01), reduced the level of reactive oxygen species and the content of malondialdehyde in mulberry seedlings and facilitated the growth and development of adventitious roots of mulberry. Transcriptomic analysis showed that GABA promoted the development and growth of adventitious roots of mulberry under saline-alkali stress by regulating the synthesis and modification of the cell wall, phytohormone signal transduction, and the conversion of starch and monosaccharides. Furthermore, the expression of pathogen pattern recognition receptors on the cell membrane of mulberry root system cells increased, enhancing the defense ability of mulberry root system cells. It is suggested that MYB, PME, SBT, EXP, DIR, POD , and the ARR family of transcription factors could be used as the target genes for further in-depth research.