Transcriptional and biochemical responses of wheat seedlings to trimethylamine N-oxide under drought stress

Abstract Drought stress is a major environmental constraint that severely limits wheat productivity worldwide. This study investigated the effects of trimethylamine N-oxide (TMAO), a novel osmolyte, on the transcriptional and physiological responses of wheat seedlings subjected to drought stress. This work provides evidence for endogenous TMAO accumulation in wheat seedlings subjected to drought stress in the absence of exogenous application. Transcriptional analyses revealed that the expression of key stress-responsive genes, including DREB , DHN , PAL , and APX , was upregulated in response to drought stress and TMAO applications. Metabolite profiling revealed that benzoic acid and salicylic acid accumulated under drought stress, with TMAO treatment modulating their levels in a stress intensity–dependent manner. Consistently, proline content was elevated under drought stress and further increased by TMAO treatment, whereas drought-induced lipid peroxidation, as indicated by malondialdehyde (MDA) levels, was significantly reduced by the osmolyte. Notably, both moderate and severe drought stress elicited distinct transcriptional, phenolic, and antioxidant responses, reflecting stress intensity–dependent regulation. Collectively, these findings suggest that TMAO mitigates drought-induced damage by contributing to protein stability and cellular homeostasis, thereby modulating molecular and biochemical pathways associated with stress tolerance.