Drought represents one of the main threats to global food security. As a response, plants have adapted their metabolism to cope with stress factors like water scarcity. Among these adaptations, polyamine (PA) metabolism plays a crucial role in regulating plant growth, development, and resilience to stress. Under stress factors, plants adjust their endogenous levels of PAs through de novo synthesis and catabolism. In Arabidopsis thaliana, a model plant species, five polyamine oxidase enzymes (AtPAO1 to 5) have been identified, which participate actively in the catabolism of superior PAs like spermidine, spermine, and thermospermine.

This research focused on the impact of water deficit (WD), defined as 20 to 30% substrate moisture, on five single Atpao mutant lines over three weeks. By using plant phenotyping approaches (non-invasive sensors), we assessed the effects of drought on various aspects of growth and photosynthetic performance for each mutant line.

Our findings revealed that WD significantly reduced water status (<RWC), biomass, rosette size, and photosynthesis across all mutant lines compared to the wild-type. Furthermore, stressed plants significantly increased foliar temperature, which adversely affected leaf transpiration rates. Interestingly, the study uncovered a variable response among the mutant lines in terms of photosynthesis capacity and leaf energy dissipation when subjected to stress, highlighting the significant contribution of PA catabolism to plant drought tolerance. Future studies addressing the biochemical and molecular profile will further elucidate the mechanism involved and the specific role of each AtPAO gene in plant adaptation to water scarcity.