Genome-wide analysis of the LAR gene family and the role of OvLAR71 in proanthocyanidin biosynthesis in Onobrychis viciifolia

Sainfoin ( Onobrychis viciifolia Scop.) is a valuable perennial forage legume abundant in proanthocyanidins (PAs). As important secondary metabolites in plants, PAs not only contribute to plant stress tolerance and defense processes, but also significantly improve forage quality. Leucoanthocyanidin reductase ( LAR ) is a key enzyme in the biosynthesis and accumulation of PAs. However, systematic research on the LAR gene family in sainfoin remains limited. Therefore, we conducted a genome-wide identification and systematic characterization of the LAR gene family in the legume forage species sainfoin. A total of 83 OvLAR genes were identified in the sainfoin genome, which were unevenly distributed across 28 chromosomes. Phylogenetic analysis classified the 83 OvLAR proteins into five evolutionary clades. Furthermore, segmental duplication served as the major driving force underlying the expansion of the OvLAR gene family. Cis-acting element profiling indicated that OvLAR gene expression is potentially regulated by both endogenous cues and environmental signals, suggesting that these genes are involved in complex regulatory networks that coordinate secondary metabolism and adaptive development. Consistently, qRT-PCR results revealed tissue-specific expression patterns among OvLAR genes, as well as differential transcriptional responses to multiple abiotic stresses. Functional assays further demonstrated that overexpression of OvLAR71 in tobacco and sainfoin significantly promoted PA biosynthesis and accumulation in leaves and flowers, accompanied by distinct changes in floral pigmentation. Collectively, this work provides the first comprehensive insight into the LAR gene family in sainfoin, offers critical insights into their roles in PA biosynthesis, and establishes a theoretical foundation for the genetic improvement of forage quality.