Synergistic physiological and transcriptomic profiling deciphers an early coordinated defense network driving...

Aluminum (Al) toxicity severely restricts sorghum growth and yield in acidic soils, particularly during seedling establishment, a stage when root systems are most vulnerable. To decode the core physiological and molecular mechanisms of Al tolerance, we screened 101 sorghum accessions and identified a highly tolerant genotype JL603 and a sensitive counterpart HYZ. Their responses to Al stress were systematically compared using integrated physiological assays and time-series transcriptome profiling. Under Al stress, JL603 maintained greatly higher relative root growth and stable root vitality, with significantly less oxidative damage, compared to HYZ. Additionally, JL603 possessed rapidly induced and sustained antioxidant enzyme (SOD, POD) activities and more pronounced accumulation of osmoregulatory substances such as proline and soluble protein. Critically, JL603 activated SbMATE and SbSTAR1/2 within 3 h, reducing root Al adsorption and shoot translocation. Transcriptome analysis indicated that JL603 employed a "precision defense" transcriptional strategy, characterized by early coordinated induction of regulatory factors (e.g., WRKY, STOP1), synergistic activation of glutathione/sulfur metabolism pathways, and superior transcriptomic stability. In contrast, HYZ exhibited widespread transcriptional dysregulation and suppressed defense pathways. Co-expression network analysis identified key tolerance-associated modules involved in tRNA metabolism and DNA repair, processes JL603 safeguards via early activation. This study demonstrates that sorghum Al tolerance arises from a coordinated "early barrier formation - redox homeostasis maintenance - precision transcriptional control" mechanism, rather than a broad-spectrum stress response. These findings provide novel insights and valuable genetic targets for breeding Al-tolerant crops.