Integrated bioinformatic and physiological analyses reveal the pivotal role of hydrogen sulfide in enhancing low-temperature tolerance in alfalfa.

Hydrogen sulfide (H2 S) is an important gaseous signal molecule that regulates plant growth and stress resistance. However, research on the H2 S synthase (HSase) genes is still limited in the model legume plant Medicago truncatula Gaertn. In the present study, a total of 40 HSase family members were first identified and analyzed in the M. truncatula genome, and these genes distributed across eight chromosomes and were clustered into five groups (I-V) based on their conserved gene structures and protein motifs. Expression analysis revealed that the MtHSase genes were expressed in all the tested abiotic stresses, albeit with expression level differences. This study also showed that H2 S improves low temperature tolerance of alfalfa seedlings by regulating the antioxidant defense system and enhancing photosynthetic capacity. Thus, the study provides new insights into how the H2 S signal regulates tolerance to low-temperature stress and provides the basis for further gene function and detection.