Abstract
BACKGROUND: Caffeic acid, one of the important phenolic compounds in plants, plays a significant role in enhancing the defense mechanisms and adaptation of plants to environmental stresses, including drought. This study aimed to investigate the effect of drought stress on the expression of genes involved in the biosynthesis of caffeic acid, photosynthetic mechanisms, and antioxidant enzyme activity in three cultivars of beans. The experiment was conducted in a split-plot design within a randomized complete block design, with three irrigation levels (50, 75, and 100% of water requirement) as the main factor and three bean cultivars (red, white, and pinto) as the sub-factor, with three replications. RESULTS: The results showed that drought stress increased the expression of caffeic acid biosynthesis genes and enhanced antioxidant enzyme activities (CAT, SOD, POD) in all bean cultivars. These responses were particularly stronger in pinto and red beans. For instance, caffeic acid content increased by more than 60% under severe drought in pinto bean tissues, contributing to improved antioxidant capacity. While drought stress reduced seed yield in all cultivars, the decline was less pronounced in pinto bean (about 14%), indicating its higher drought tolerance compared to the white bean, which showed a larger yield reduction. CONCLUSIONS: These results suggest that the increased expression of genes involved in caffeic acid biosynthesis and the enhancement of antioxidant activity are key mechanisms in plant adaptation to drought. Identifying and utilizing these mechanisms can provide effective strategies for genetic improvement and the production of drought-resistant cultivars. Moreover, the findings can contribute to optimizing irrigation management and improving production sustainability in arid and semi-arid regions.