Unravelling Mechanisms of Acquired Drought Tolerance by Priming in Tomato Using Integrative Multi-Omics Phenotypic...

The escalating frequency and intensity of recent droughts threaten global crop production and food security. Although drought priming is crucial for plant drought resilience, the mechanisms imparting drought stress memory remain poorly understood, especially in crops such as tomato. This study elucidates the mechanisms of drought stress memory in tomato by integrating phenotypic screening with transcriptomic and proteomic analyses. Initial screening of 30 genotypes identified varieties with contrasting basal drought tolerance as indicated by gas exchange and drought damage index. Subsequent priming experiments revealed that acquired drought tolerance is independent of basal resistance, with both sensitive and tolerant genotypes exhibiting enhanced adaptation. Priming improved photosynthetic capacity and water use efficiency via optimised stomatal regulation. Moreover, elevated reactive oxygen species (ROS), particularly H₂O₂, was a key signalling molecule that initiated the drought memory establishment. This acquired drought tolerance was stress-specific, enhancing tolerance of tomato plants to subsequent drought but not heat stress. Integrative multi-omics analysis identified 518 memory-associated transcripts and pinpointed key candidate genes, including HSP90 (heat shock protein 90), WRKY26 and WRKY31 (WRKY transcription factor 26/31), which were linked to central pathways such as MAPK (mitogen-activated protein kinase) signalling and phenylpropanoid biosynthesis. The VIGS (Virus-Induced Gene Silencing) assay further demonstrated that WRKY26 functions as a negative regulator of acquired drought tolerance. Our work established a mechanistic framework for drought stress memory, highlighting ROS signalling and memory-specific gene networks. These insights, along with the generated datasets, provide valuable resources for the strategic breeding of climate-resilient tomato varieties.