Metabolomic insights into tolerance mechanisms of the desert shrub Haloxylon salicornicum during drought and recovery

Abstract

Desert plants exhibit remarkable adaptive mechanisms that enable them to survive extreme aridity through efficient water management and metabolic plasticity. This study investigated the metabolomic basis of drought tolerance in the xero-halophyte Haloxylon salicornicum, focusing on organ-specific metabolic responses and post-drought recovery processes. Using untargeted metabolomics approach, the metabolic profiles of seedlings subjected to 15 days of water withholding followed by 15 days of rewatering were analyzed. Drought exposure induced the accumulation of 25 metabolites in shoots and 24 in roots, among which three compounds, glutathione, leucine, and N-acetylputrescine were consistently and significantly upregulated in both organs. These shared metabolites represent potential markers of drought response in H. salicornicum. Shoots specifically accumulated metabolites such xylulose, xylitol, and galacturonate, which are implicated in cuticle biosynthesis and cell wall remodeling, as well as amino acids (aspartate and asparagine) and tricarboxylic acids supporting energy supply and C-N balance under drought. In contrast, roots specifically exhibited elevated levels of osmolytes (e.g., β-alanine and γ-aminobutyrate), the polyamine putrescine, glycerol and UDP-glucuronate, which is associated with cell wall reinforcement. Following rehydration, seedlings did not fully return to the pre-stress metabolic state and significantly maintained elevated levels of stress-related metabolites. These findings provide valuable insights into the metabolic networks underlying drought adaptation and recovery in H. salicornicum, underscoring its potential as a model system for elucidating the mechanisms that enable desert plants to withstand extreme drought conditions.