Divergent regulation of trehalose accumulation by exogenous proline in drought-stressed sorghum and maize

Abstract

This study investigated the effects of varying water availability and exogenous proline application on trehalose accumulation in two economically important crops, sorghum (Sorghum bicolor L.) and maize (Zea mays L.), which exhibit distinct drought tolerance strategies. The experiment was conducted under controlled conditions with four water availability levels (100%, 75%, 50% and 25%) and three proline concentrations (200, 400, and 600 mg/L). Leaf area and leaf curling were also measured to verify the successful establishment of drought stress prior to biochemical analyses. Trehalose content was determined at the V8 growth stage using a modified enzymatic assay. Results showed a reduction in leaf area with decreasing water availability and a concurrent rise in leaf curling, confirming effective induction of drought stress. Maize displayed stronger curling responses, whereas sorghum largely maintained leaf structural integrity. Regarding trehalose, sorghum naturally accumulated higher levels under severe drought stress without proline, indicating a robust innate stress response. In contrast, maize exhibited lower trehalose levels under the same conditions but showed a marked increase with proline application, suggesting a greater reliance on external osmoprotectants. Under moderate and mild stress, proline enhanced trehalose accumulation in both crops, though the response was more consistent in sorghum. Interestingly, under optimal water conditions, proline application increased trehalose levels in sorghum but had minimal effect on maize, highlighting differences in the metabolic utilization of proline. Overall, these findings underscore the importance of tailoring proline application strategies based on crop-specific stress responses and environmental conditions to optimize drought resilience. This study provides valuable insights into the complex interplay between water availability, proline, and trehalose metabolism, offering potential pathways for improving crop stress tolerance in drought-prone regions.