Exogenous application of acetoin promotes tomato seedling growth and alters the transcriptome profile

Microbially derived volatile organic compounds can influence plant growth and bolster systemic resistance; however, the respective transcriptional changes are unclear. This study focused on acetoin, a specific volatile organic compound, to assess its impact on the growth of tomato seedlings across various concentrations. In a hydroponic experiment, optimal growth was observed at a concentration of 0.5 g L⁻¹ acetoin, which also facilitated an increase in photosynthetic activity in the seedlings. At 6 hours, a total of 796, 62, and 114 differentially expressed genes (DEGs) were identified in the leaves, stems, and roots, respectively. After 24 hours, the numbers increased significantly to 517, 450, and 3,981, respectively, comprising predominantly upregulated DEGs. The DEGs were annotated using the Kyoto Encyclopedia of Genes and Genomes database, revealing significant enrichment in pathways related to plant hormone signal transduction and plant-pathogen interactions. The pronounced upregulation of genes associated with stress responses and auxin biosynthesis likely contributed to enhanced plant growth and stress resilience. Physiological assessments indicated that acetoin treatment significantly increased the levels of indole-3-acetic acid, abscisic acid, jasmonic acid, glycosylated salicylic acid, and trans-zeatin in tomato leaves, ultimately facilitating seedling growth. These results suggest potential molecular targets for the breeding of stress-resistant crops and highlight the promising application of acetoin as a microbial fertilizer.