Conclusion
Plants adapt to unfavorable environmental conditions by dynamic development at physiological, biochemical, and morphological levels. These complex responses involve several signaling, metabolites, transcription factors, and hormones. Our results strengthen the concept of stress interaction, pointing out as the combined heat and drought stress is not merely the combination of the single stresses but rather the result of a multi-level interaction that involves specialized metabolites and a complex remodelling of phytohormones. Intriguingly, the metabolomics signatures were shaped in a coordinated manner with root and rhizosphere bacterial microbiota, suggesting the complete plant holobiont should be considered when studying the responses of plants to abiotic stresses. In fact, a complex series of stress sensors and stress signaling processes is likely orchestrating the responses at plant and microbiota levels to mediate plant microbiota assembly and promote a harmonized modulation of stress mitigation processes.