Dose-dependent aluminum stress responses in Lotus corniculatus: integrated morphological, physiological and transcriptomic analysis with WGCNA
Aluminum (Al) toxicity is a major constraint to crop and forage production on acid soils, which occupy a substantialfraction of the world's arable land. This study characterizes the dose-dependent response of the forage legume Lotuscorniculatus (birdsfoot trefoil, cv. Qiangui No.1) to aluminum stress and identifies candidate gene resources forbreeding Al-tolerant cultivars. Plants were grown hydroponically under five Al3+ concentrations (0, 2.0, 4.0, 6.0, and10.0 mmol/L; pH 4.3) for 15 days. Root and leaf morphological traits and physiological indices (antioxidant enzymeactivities, proline, and H2O2 contents) were measured, and root tissues were analyzed by RNA sequencing combined withdifferential expression analysis, transcription factor profiling, and weighted gene co-expression network analysis(WGCNA). The dataset captures a three-phase adaptive strategy: a low-dose hormetic response at 4.0 mmol/L (rootsurface area increased 94.1% versus control), a major defense-switching threshold at 6.0 mmol/L (7,274 differentiallyexpressed genes, 99.96% up-regulated, with large-scale activation of 115 transcription factors including 19 C2H2zinc-finger factors and a STOP1-like regulator), and a high-dose damage-buffering phase at 10.0 mmol/L marked byenhanced flavonoid and phenylpropanoid secondary metabolism. WGCNA resolved three core co-expression modulesassociated with antioxidant defense and growth maintenance, DNA repair and oxidative damage response, and morphologyenhanced flavonoid and phenylpropanoid secondary metabolism. WGCNA resolved three core co-expression modulesassociated with antioxidant defense and growth maintenance, DNA repair and oxidative damage response, and morphologymaintenance and energy metabolism, from which candidate hub genes and regulatory transcription factors (bZIP, C2H2,NAC, MYB) were prioritized. These data provide a foundational transcriptomic resource for understanding aluminumtolerance in forage legumes and deliver candidate genes for functional validation and marker-assisted selection inbirdsfoot trefoil and related legumes on acid soils.