Enhanced Photosynthesis and Water-Use Efficiency in Transgenic Sugarcane Expressing Arabidopsis <em>DREB1A</em> Under Drought Stress

Drought stress imposes a critical limitation on sugarcane productivity, thereby necessitating the development of stress-resilient cultivars for sustainable agriculture. The present study aimed to enhance drought tolerance in sugarcane by introducing the Arabidopsis DREB1A gene under the control of the stress-inducible rd29A promoter. Transgenic sugarcane lines were generated via particle bombardment-mediated transformation and subsequently evaluated through molecular, physiological, and agronomic assessments under controlled and drought-stressed conditions. Molecular analysis confirmed stable transgene integration, with transgenic lines exhibiting up to a 10-fold increase in DREB1A expression relative to wild-type plants. Physiological assessments demonstrated that, under drought stress at 60% field capacity (FC), transgenic lines maintained photosynthetic rates (PN) that were 224-270% higher, stomatal conductance (gs) increased by 84-167%, and relative water content (RWC) was enhanced by 25-31% compared to non-transgenic controls. Moreover, the leaves of transgenic sugarcane displayed improved osmotic regulation and water-use efficiency. Agronomic evaluations further revealed significant improvements in plant growth and productivity. Under drought stress (60% FC), transgenic lines exhibited 76-109% greater cane height, with cane diameter 71-86% larger. Shoot biomass increased by 39-87%, and root biomass was enhanced by 65-103%. Additionally, the Brix percentage, indicative of sucrose accumulation, increased by 36-55% in the transgenic plants at 60% FC. These findings establish a robust correlation between DREB1A expression, enhanced physiological resilience, and improved agronomic performance under drought conditions. The capacity of DREB1A-expressing transgenic sugarcane to sustain higher photosynthetic activity, superior water-use efficiency, and increased biomass accumulation underscores its potential as a genetic strategy for developing drought-resilient sugarcane varieties. This study offers novel insights into the molecular mechanisms underlying drought tolerance and provides a promising approach for ensuring sustainable sugarcane cultivation in water-scarce regions.