From molecular dialogue to ecological resilience: The holobiont as a model for plant adaptation to drought

The concept of the plant holobiont, encompassing the host plant and its associated microbes, represents a significant shift in our understanding of plant adaptation to drought conditions. This review brings together current understanding of the molecular interactions between plants and their associated microbiomes that play a role in developing resilience to water scarcity. We explore the deep evolutionary roots of plant-microbe relationships, showing that drought tolerance is not just an intrinsic trait of plants but a co-evolved feature of the holobiont. At the rhizosphere interface, intricate signalling networks, like the "cry-for-help" strategy, orchestrate the assembly of the microbiome during times of stress. Beneficial microbes employ five distinct strategies for self-protection: forming biofilms with extracellular polymeric substances, producing osmoprotectants, utilizing antioxidants, modifying phytohormones (notably via ACC deaminase), and releasing signalling molecules. These components function collaboratively at various tiers, ranging from offering direct physical defence to preparing the entire system for optimal performance. The genetic structure of the host plays a significant role in the recruitment of the microbiome in a way that can be inherited, thereby supporting strategies for breeding that leverage the microbiome. Ecological factors, including legacy effects, land-use context, and meta-holobiont networks, significantly contribute to resilience. To implement these concepts effectively, we must employ a combination of synthetic consortia, biostimulants, and responsible soil management. The holobiont framework reinterprets drought adaptation as a collective, co-evolved trait, offering a ground-breaking foundation for sustainable crop resilience amid increasing climatic dryness.

Dr. Amir Abdullah Khan is a plant scientist specializing in plant stress physiology, plant–microbe interactions, and environmental stress resilience. He holds a PhD in Plant Science from Nankai University, China, and has conducted postdoctoral research at Jiangsu University. Currently He is serving as a postdoctoral fellow at Anhui Normal University, Wuhu, Anhui China. His research focuses on plant growth-promoting bacteria, salinity and drought tolerance, rhizosphere processes, and emerging contaminants including microplastics. He has published extensively in plant and environmental sciences and has experience in physiological, biochemical, microbiological, and molecular approaches to understanding plant stress responses and developing sustainable strategies for climate-resilient agriculture.