Drought-induced root architectural responses in lettuce (Lactuca sativa L.): Genotype-specific mechanisms revealed by...

As global climate change intensifies, drought has emerged as one of the most severe abiotic stresses, significantly constraining plant growth and jeopardizing global agricultural productivity. Understanding the responses of the plant root system architecture (RSA) to soil water deficit at both the physiological and molecular levels is critical for enhancing drought resistance. In this study, comparative physiological and time-course transcriptomic analyses were performed on two different lettuce genotypes: LSL (drought-tolerant) and SML (drought-sensitive). The results showed that drought stress induced significant oxidative damage and lipid peroxidation in lettuce, while increasing antioxidant enzyme activities and osmolyte accumulation. Root system architecture (RSA) was markedly impaired, with greater severity in the drought-sensitive genotype (SML). Transcriptomic analysis identified numerous differentially expressed genes (DEGs), with 2177 and 1363 key candidate DEGs detected in the tolerant (LSL) and sensitive (SML) genotypes, respectively. Weighted gene coexpression network analysis revealed distinct regulatory mechanisms: plant hormone signal transduction and MAPK signaling pathways were enriched in LSL, while DNA replication and repair pathways were enriched in SML. Key hub genes associated with RSA traits were identified, including auxin-responsive genes in LSL and cell cycle genes in SML. These findings provide valuable insights into the genotype-specific mechanisms of drought adaptation and offer target genes for breeding drought-resistant lettuce cultivars.