The homeostasis of β-alanine is key for Arabidopsis reproductive growth and development

β-Alanine, an abundant non-proteinogenic amino acid, acts as a precursor for coenzyme A and plays a role in various stress responses. However, a comprehensive understanding of its metabolism in plants remains incomplete. Previous metabolic genome-wide association studies (mGWAS) identified ALANINE:GLYOXYLATE AMINOTRANSFERASE2 (AGT2, AT4G39660) linked to β-alanine levels in Arabidopsis under normal conditions. In this study, we aimed to deepen our insights into β-alanine regulation by conducting mGWAS under two contrasting environmental conditions: control (12 h photoperiod, 21°C, 150 μmol m^-2 sec^-1) and stress (harvested after 1820 min at 32°C and darkness). We identified two highly significant quantitative trait loci (QTL) for β-alanine, including the AGT2 locus associated in both environments and ALDEHYDE DEHYDROGENASE6B2 (ALDH6B2, AT2G14170) associated only under stress conditions. A coexpression-correlation network revealed that the regulatory pathway involving β-alanine levels, AGT2, and ALDH6B2 connects the branched chained amino acid (BCAA) degradation through the propionate pathway. Metabolic profiles of AGT2 overexpression (OE) and knock-out (KO) lines (agt2) across various organs and developmental stages established the critical role of AGT2 in β-alanine metabolism. This work underscores the importance of β-alanine homeostasis for proper growth and development in Arabidopsis.