Synchronization and interaction of proline, ascorbate and oxidative stress pathways under abiotic stress combination in tomato plants
Adverse environmental conditions, such as salinity, heat waves, or water scarcity have a devastating impact on plant productivity. In nature, multiple abiotic stresses occur simultaneously and plants evolved unique responses to cope against combination stress that are not induced under a single stress condition. Here we coupled genome-wide transcriptional profiling and untargeted metabolomics with physiological and biochemical analyses to characterize the effect of salinity and heat applied jointly in the metabolism of tomato plants. Our results demonstrate that combination of salinity and heat causes unique reprogramming of tomato metabolic pathways, including changes in the expression of 1,388 genes and accumulation of 568 molecular features. Pathway enrichment analysis of transcript and metabolite data indicated that the proline and ascorbate pathways act synchronously to maintain cellular redox homeostasis, which was supported by measurements of enzymatic activity and oxidative stress markers. We also identified key transcription factors from the basic Leucine Zipper Domain (bZIP), Zinc Finger Cysteine-2/Histidine-2 (C2H2) and Trihelix families that are likely regulators of the identified up-regulated genes under salinity and heat combination.  Our results expand the current understanding of how plants acclimate to environmental stresses in combination and unveiled the synergism between key cellular metabolic pathways for effective reactive oxygen species detoxification. Our study opens the door to elucidating the different signaling mechanisms for stress tolerance. Overall design: Genome-wide transcriptional profiling to characterize the effect of salinity and heat applied jointly in the metabolism of tomato plants.