Molecular and physiological characterizations of roots under drought stress in rice: A comprehensive review

Drought stress poses a major challenge to rice (Oryza sativa L.) production, significantly threatening global food security, especially in the context of climate change. Root architecture plays a key role in drought resistance, as rice plants require substantial water throughout their growth. The genetic diversity of rice root systems exhibits various growth patterns and adaptive traits that enable plants to endure water-deficient conditions. Harnessing this diversity to improve drought resilience demands a thorough understanding of critical root traits and adaptive mechanisms. This review explores rice roots' anatomical, physiological, and biochemical responses to drought, emphasizing important traits such as root architecture, xylem vessel modifications, root cortical aerenchyma (RCA), and water transport mechanisms. The role of biochemical regulators, including phytohormones, sugars, lipids, and reactive oxygen species (ROS), in root adaptation to drought is also explored. Additionally, the genetic and molecular pathways influencing root development under drought stress are discussed, with a focus on key genes and transcription factors (TFs) such as NAC, bZIP, AP2/ERF, and others that contribute to enhanced drought tolerance. Understanding these complex interactions is crucial for breeding drought-tolerant rice varieties, ultimately improving crop productivity under challenging environmental conditions.