Network analysis of metabolomics, transcriptome and hormones reveals propionic acid-mediated novel survival strategy against drought in wheat.

Propionic acid (PA), a low-molecular-weight organic acid, is crucial to plant life metabolism. However, the regulatory mechanism of PA-mediated drought resistance in wheat remains largely unknown. Herein, we reported on a regulatory network of PA-mediated drought resistance in wheat using integrated transcriptome and metabolomics analysis and verified genes associated with drought resistance. Compared to the water-treated group, the application of PA alleviated the damage of drought by increasing plant water content, antioxidant enzyme activities and decreasing the malondialdehyde level (MDA). Transcriptome and metabolomics analysis revealed that PA triggered upregulation of key genes and metabolites, including TaBCAT, TaALDH6A1, TaALDH7A1, TaCHI, TaFLS, chrysin, and galangin, which were involved in valine, leucine and isoleucine degradation or flavonoid biosynthesis, respectively. In addition, the expression of genes encoding auxin-related transcription factors (TFs) strikingly increased, such as auxin/indoleacetic acid (AUX/IAA) and auxin response factor (ARF). Moreover, PA activated abscisic acid (ABA) and indole-3-acetic acid (IAA) signalling pathways. Taken together, our findings suggest that PA promotes energy metabolism and antioxidant activities to confer wheat drought resistance by introducing comprehensive and systemic effects of valine, leucine and isoleucine degradation flavonoid biosynthesis. Furthermore, activated AUX/IAA and ARF TFs might serve vital roles in drought resistance via modulating IAA signalling. This study provides novel insights into PA-mediated crop resistance and the improvement of the agroecological environment.