Redox and osmotic homeostasis: Central drivers of drought resilience in grapevine rootstocks.

A comparative study of two grapevine rootstocks with contrasting drought stress responses revealed that the drought-resilient RUG harbors an efficient antioxidant defense system, characterized by increased activities of superoxide dismutase (SOD), glutathione peroxidase (GPX), and catalase (CAT), along with elevated proline (Pro) levels compared to the drought-sensitive MGT. This robust scavenging machinery enables RUG to maintain redox balance, effectively mitigating oxidative stress and preserving cellular integrity during drought. Anatomical evaluations showed severe xylem disruptions in MGT, including extensive tylosis, leading to leaf necrosis and impaired water transport. Conversely, RUG maintained a structurally intact and functional xylem, crucial for sustaining hydraulic conductivity and water supply during drought. The pronounced rise in Pro underscores its critical role in drought resilience, working synergistically with other cellular components to facilitate osmotic adjustment while detoxifying reactive oxygen species (ROS) and minimizing oxidative damage. Transcriptome profiling suggested that RUG displays sequential gene expression during drought driven by distinct molecular processes for photosynthesis, osmotic adjustment, and structural remodeling, a dynamic notably absent in MGT. These findings emphasize the complex interplay of osmotic and oxidative homeostasis in RUG, illustrating the adaptive mechanisms that contribute to its drought resilience, potentially guiding future rootstock selection and breeding strategies.