Metabolic Responses to Salinity Identify a Role for Mitochondrial 2-Oxoglutarate Dehydrogenase in Wheat Tissue Tolerance

Wheat is a staple crop crucial for global food security, but its production is significantly affected by salt stress. Exploring natural genetic diversity in wheat can identify ways to improve salt tolerance. We subjected five wheat genotypes: Mocho de Espiga Branca (enhanced tissue tolerance), Fretes (tissue tolerance), Wyalkatchem and Westonia (salt exclusion) and Westonia Nax1 (enhanced salt exclusion), to 150 mM NaCl for 8 days. We measured changes in biomass, photosynthesis, chlorophyll content, Na+/K+ ratios and protein abundance. Mocho maintained growth despite high tissue Na+, showing physiological tolerance supported by differential regulation of mitochondrial proteins, central carbon metabolism, the GABA shunt and compatible solutes. Mitochondrial complexome profiling revealed salt-induced instability of 2-oxoglutarate dehydrogenase complex (OGDC) and a hydroxyglutarate synthase orthologue (HglS). In vitro assays confirmed subtle but significant OGDC activity and stability differences in Mocho, which also retained higher TCA cycle enzyme levels in vivo. Whole-plant treatment with the OGDC inhibitor succinyl phosphonate reproduced salt-like reductions in chlorophyll and biomass, particularly in Mocho. These findings highlight distinct strategies of tissue tolerance and salt exclusion in wheat, emphasising OGDC's role in Mocho's salt tolerance and pointing to metabolic pathways that could improve tissue tolerance traits and support sustainable agriculture.