Titanium ions promote tomato growth and increase stress resistance.

Background: Titanium ions can significantly promote plant growth and increase crop yield, yet the underlying mechanism remains an enigma. This study investigated the effect of titanium ions on tomato (Solanum lycopersicum) by foliar spraying and root irrigation with titanium ion solution (8 mg/L) in both pot and field trials.

Results: Pot and field trials showed that exogenous titanium ions significantly stimulated plant growth and root system development, enhanced antioxidant capacity, alleviated Blossom end rot and saline-alkali stress. After 24 h foliar application, comparative RNA-Seq profiling of leaves identified 4,214 differentially expressed genes. GO and KEGG enrichment analyses revealed that titanium ions affected core pathways such as DNA replication, protein translation, phenylpropanoid biosynthesis, plant-pathogen interaction, and plant hormone signal transduction in tomato. Notably, virtually all the genes associated with DNA replication and ribosome translation were remarkably upregulated. Other important upregulated genes included the phytohormone related genes (e.g., auxin, ethylene and gibberellin) and stress-related transcription factor genes (e.g., MYB13, WRKY46, WRKY51, WRKY54, PLT2, ANT, and CRF2). The qRT-PCR validated the RNA-Seq results with high concordance.

Conclusions: This study partially elucidates the mechanisms by which titanium ions promote plant growth and enhance abiotic stress resilience, providing guidance for the application of titanium ion-based biostimulants in agricultural production.