Wheat is one of the major staples worldwide, yet it is significantly affected by salt stress. Exploring the natural genetic diversity in wheat is the key to improving salinity tolerance. Five wheat genotypes, differing in salt tolerance, were subjected to 150 mM NaCl stress for 8 days. Changes in biomass, photosynthesis, chlorophyll content and Na+/K+ content were measured.

Despite the higher tissue salt levels, wheat genotype Mocho showed greater physiological tolerance to salinity. Shotgun proteomics and metabolomics of the leaf samples confirmed the differential regulation of proteins located in mitochondria and metabolites generated in mitochondria in the 5 genotypes under salt stress. Subsequent mitochondrial complexome profiling identified 2-oxoglutarate dehydrogenase (OGDC) and a plant hydroxyglutarate synthase orthologue (HglS) as enzymes in complexes that significantly lose structural stability and dissociate into subunits under salt stress.

In vitro activity assays and proteome profiling showed Mocho's ability to retain higher OGDC activity and higher OGDC subunit abundance under salt stress. In planta and leaf disc assays using the OGDC inhibitor succinyl phosphonate (SP), salt-like symptoms of decreased chlorophyll content and plant biomass were observed.

These effects were significantly more apparent in the tissue-tolerant Mocho landrace than in other excluder varieties, indicating an enhanced role of OGDC in its metabolism. Intriguingly, OGDC exhibited the capacity to oxidize both 2-oxoglutarate (OG) and 2-oxo adipate (OA), which is also the substrate of HglS in the lysine degradation pathway.

Mocho's OGDC demonstrated a heightened catalytic rate using OA under salt stress compared to salt-excluding varieties, showcasing its robust ability to sustain both the TCA cycle and lysine degradation functions. This altered substrate preference of OGDC in Mocho underscores its importance in the metabolic landscape of the variety, suggesting a putative role in salt tissue tolerance.

The enhanced performance of OGDC in tissue-tolerant Mocho under salt stress would be a promising prospect for developing salt-tolerant wheat varieties, enhancing global wheat production.