Transcriptional coordination enhances folate biosynthesis in dry common bean grains during storage.

Postharvest storage critically influences seed physiology and nutritional quality. Common beans (Phaseolus vulgaris) are a rich source of folates, vitamins that are typically unstable and degrade during storage. We investigated three varieties (from Mesoamerican and Andean origins) over 180 days under different conditions and found significant accumulation of folates and their more stable polyglutamylated derivatives. Transcriptomic analysis under controlled storage (15 °C, 55% relative humidity) revealed consistent upregulation of genes catalyzing key steps in folate biosynthesis (GTP cyclohydrolase I and Aminodeoxychorismate lyase), along with transporters and polyglutamylation enzymes in the three varieties. In contrast, most one‑carbon metabolism genes were downregulated, except for mitochondrial Serine hydroxymethyltransferase 1 and 5,10-Methylenetetrahydrofolate dehydrogenase/cyclohydrolase 1. Concomitantly, the corresponding one‑carbon metabolism related amino acids and total protein decreased. Interestingly, genes involved in de novo purine biosynthesis, a folate-dependent pathway, were upregulated, whereas cell cycle-related genes showed moderate transcriptional activation. These results demonstrate that dry seeds maintain transcriptional and metabolic activities influenced by storage conditions. This work provides new insights for preserving folate content and nutritional quality in legumes and opens relevant questions about seed metabolism during storage.