Abstract
The increasing frequency of concurrent heat waves and drought events under climate change poses a major challenge to crop productivity and climate resilience. However, the molecular basis of crop adaptation to combined heat–drought stress (CHDS) remains insufficiently understood because responses to combined stresses cannot be adequately explained by the linear superposition of individual heat or drought responses. This review addresses the central question of how plants integrate multiple environmental signals to achieve adaptive regulation under CHDS. By synthesizing recent advances in stress perception, signal transduction, transcriptional reprogramming, hormonal crosstalk, metabolic adjustment, and post-transcriptional/post-translational regulation, we highlight that CHDS induces a dynamic reorganization of regulatory networks characterized by non-additive responses, context-dependent signaling priorities, and trade-offs between growth maintenance and stress defense. We further propose a systems-level framework in which Ca²⁺ and reactive oxygen species signaling act as early information-processing modules, transcription factor networks and hormone interactions function as regulatory integration layers, and multi-omics-driven network modeling facilitates the identification of potential regulatory hubs. Current limitations, including insufficient field validation, genotype- and developmental stage–dependent variability, and incomplete integration of root–rhizosphere interactions, are critically evaluated. Finally, emerging strategies involving dynamic modeling, multi-omics-guided target discovery, gene editing, synthetic biology, and microbiome-based regulation are discussed to advance the rational improvement of combined stress tolerance. This review establishes a network-based conceptual framework for understanding crop adaptation to concurrent heat and drought stresses and provides theoretical foundations for developing predictive and design-oriented approaches toward climate-resilient agriculture.
