Physiological, hormonal and molecular dynamics of root system architectural response to drought stress signaling in crops

Drought represents one of the most devastating environmental challenges, exerting deleterious effects on agricultural productivity worldwide. Plants are particularly susceptible to drought stress, undergoing a series of physiological, biochemical, and molecular disturbances. Roots are pivotal in modulating plant responses toward drought stress, influencing plant development. Under stress conditions, plant roots play a major role in altering the soil structure through various mechanisms such as anchorage, penetration, and the exudation of certain organic compounds into the rhizosphere. The current review provides a comprehensive summary of research on root-mediated plant responses to drought stress, emphasizing the importance of root hydraulic conductivity and other adaptive mechanisms regulating morphological attributes and root system architecture. The review also encompasses the role of root-soil dynamics in the rhizosphere in coping with drought stress. Additionally, it explores the role of phytohormones such as abscisic acid, auxin, cytokinin, and ethylene as well as of key transcription factors such as DREB, AREB, MYB, bZIP, and NAC, which regulate these phytohormones to modulate root system architecture to put up defense against drought stress. Further, the review examines how roots perceive and respond toward drought stress through signaling mechanisms, as well as how drought stress alters the metabolic status to maintain cellular homeostasis under water-deficit conditions. A deeper understanding of molecular and hormonal signaling crosstalk will contribute toward engineering crop varieties with enhanced plasticity traits as well as yield stability and sustainability in the changing climatic scenario.