Genome-Wide Identification of Juglans regia GABA Transcription Factors and Expression Pattern Analysis in Response to...

Background/Objectives: γ-aminobutyric acid (GABA), a non-protein amino, is synthesized from glutamic acid through the catalytic activity of glutamate decarboxylase (GAD). As a key signaling molecule, GABA plays a vital role in plant responses to abiotic stresses. To explore the potential involvement of the GABA gene family in Juglans regia's response to environmental stressors, a comprehensive genome-wide identification and analysis of GABA-related genes was performed. Methods: The study examined their protein features, evolutionary relationships, chromosomal locations, and promoter cis-regulatory elements. Additionally, the expression patterns of GABA family genes were analyzed in J. regia seedlings subjected to salt and drought stress. Results: Genome analysis identified three main components of the GABA metabolic pathway in J. regia: glutamate decarboxylases (GADs), GABA transaminases (GABA-Ts), and succinic semialdehyde dehydrogenases (SSADHs). These genes were unevenly distributed across 14 chromosomes, with chromosome 10 containing the highest number. Promoter analysis revealed that about 80% of cis-acting elements were linked to plant hormone regulation, such as abscisic acid (ABA), and stress responses, including drought and high-salinity. Phylogenetic analysis showed that JrGAD1 was distantly related to other JrGAD members, while certain JrGABA-T and JrSSADH genes formed closely related pairs. Under salt and drought stress, JrSSADH23 expression was highly upregulated (2.60-fold and 2.24-fold, respectively), a trend observed for most JrSSADH genes. Conclusions: These findings offer valuable insights into the molecular basis of GABA metabolism in J. regia's stress adaptation and identify promising genetic targets for developing stress-tolerant varieties.