Identification and Expression Analysis of the GAD Gene Family in Tomato

Objective Plant glutamate decarboxylase (GAD) plays a pivotal role in the biosynthesis of γ-aminobutyric acid (GABA), which is involved in plant growth, development, and stress responses. However, the functional divergence among members of the tomato GAD gene family and their specific molecular regulatory networks remain unclear. This study aims to systematically characterize the tomato GAD gene family, including its genomic distribution, structural features, and evolutionary relationships, providing a theoretical basis for its application in molecular mechanism research and genetic improvement.

Method Conduct a comprehensive bioinformatics analysis on the members of the tomato GAD gene family, includingchromosome localization, gene structure, physicochemical properties of proteins, phylogenetic relationships and tissue-specific expression analysis.

Result The tomato genome contains five glutamate decarboxylase (GAD) genes localized to chromosomes 1, 3, 4, 5, and 11, all featuring canonical intron-exon structures. The encoded GAD proteins are unstable and predominantly cytoplasmic-localized, with α-helices and random coils constituting their dominant secondary structures; their active sites and functional domains are evolutionarily conserved. While tomato GAD genes show high sequence similarity to orthologs in Oryza sativa and Arabidopsis thaliana, specific amino acid variations exist within critical functional domains. In the wild tomato accession 'G173, (Guangxi origin), GAD genes exhibited no detectable expression in roots, stems, or leaves but displayed significant tissue-specific expression differences in flowers and fruits. Solyc01g00002 and Solyc04g001008 showed relatively high expression, whereas Solyc03g002270 maintained comparable expression levels in both floral and fruit tissues.

Conclusion Tomato GAD genes exhibit significant variations in gene structure and protein properties, while containing multiple conserved functional domains. Phylogenetic analysis revealed that tomato GADs share close homology with their orthologs in species such as A. thaliana and O. sativa. Furthermore, they display distinct tissue-specific expression patterns in roots, stems, leaves, and fruits, suggesting that this gene family may play extensive roles in the growth and development of tomato.