Succinic acid synthesis regulated by succinyl-coenzyme A ligase (SUCLA) plays an important role in root response to alkaline salt stress in Leymus chinensis

Alkaline salts have more severe adverse effects on plant growth and development than neutral salts do. However, the adaptive mechanisms of plants to alkaline salt stress remain poorly understood, especially at the molecular level. The Songnen Plain in northeast China is composed of typical 'soda' saline-alkali soil, with NaHCO₃ and Na₂CO₃ as the predominant alkaline salts (pH ≥ 9.2). Leymus chinensis can grow on this saline-alkali land, showing strong adaptability. We investigated the role of succinic acid and genes regulating its synthesis in the response to alkaline salt stress in L. chinensis roots. Compared to the neutral salt (NaCl) and high pH treatments, the alkaline salt (NaHCO₃ and Na₂CO₃) treatment specifically caused changes in 11 organic acids, of which the increase in succinic acid was the greatest. The exogenous addition of succinic acid alleviates the damage of alkaline salt to L. chinensis roots. Further, two genes encoding succinyl-coenzyme A ligase (SUCLA) subunits that regulate succinic acid synthesis, LcSUCLAα and LcSUCLAβ, were identified; these genes interact and were localized within mitochondria. Overexpression of LcSUCLAα and LcSUCLAβ caused an increase in succinic acid and enhanced tolerance of NaHCO₃ in transgenic rice seedlings. These results suggest that LcSUCLAα and LcSUCLAβ may be involved in the response to alkaline salt stress through the regulation of succinic acid synthesis.