OsLdh3 interacts with OsGAPC3 and OsLos2 to maintain the glycolytic continuum for tolerance to multiple abiotic stresses in rice

Lactate dehydrogenases are oxidoreductases present in almost all living organisms. They catalyze the interconversion of pyruvate and L-lactate with simultaneous oxidation of NADH and reduction of NAD+. Since their function remains largely unexplored in rice, in this study we deciphered the role of the rice lactate dehydrogenase, OsLdh3. OsLdh3 showed optimum enzyme activity at pH 6.6 for the forward reaction (pyruvate to L-lactate) and pH 9 for the reverse reaction (L-lactate to pyruvate). Protein-protein interaction studies revealed that OsLdh3 interacts with the glycolytic enzymes glyceraldehyde 3-phosphate dehydrogenaseC3 (OsGAPC3) and Enolase2 (OsLos2), suggesting its role in regulating glycolytic flux. Further, overexpression of OsLdh3 in rice showed enhanced abiotic stress tolerance by exhibiting elevated NAD+ levels and OsGAPC3 activity, thereby facilitating an improved glycolytic continuum and higher pyruvate accumulation. Consequently, these lines also showed increased mitochondrial respiration and ATP synthesis, and reduced reactive oxygen species (ROS) accumulation. Further, enhanced photosynthetic efficiency and reduced yield penalty of the stress-imposed OsLdh3 overexpression lines underscore its importance in crop productivity under adverse climatic conditions. Thus, our findings show that OsLdh3 enhances stress tolerance in rice by regulating redox homeostasis and respiration, reducing ROS levels, and maintaining energy balance. This makes OsLdh3 a promising candidate gene for developing climate-resilient rice cultivars with reduced yield gap.