Comparative physiological, transcriptome, and qRT‐PCR analysis provide insights into osmotic adjustment in the licorice species Glycyrrhiza inflata under salt stress

Licorice (Glycyrrhiza spp.) is a versatile industrial and fodder crop with important medicinal, economic, and forage values. However, little is known about their salt tolerance mechanisms. Here, to investigate the osmotic adjustment mechanism of Glycyrrhiza inflata, a licorice species with excellent adaptation to the severe saline habitat, we compared the growth, the contributions of major osmolytes to osmotic potential, and the expression of genes associated with the accumulation of major osmolytes under salt stress between G. inflata and Glycyrrhiza uralensis, another licorice species mainly grown in mild salinized regions. The results showed that G. inflata displayed stronger salt tolerance than G. uralensis. Compared with G. uralensis, G. inflata accumulated higher contents of proline, betaine, and soluble sugars, as well as Na+ and NO3− in roots, and meanwhile, accumulated higher concentrations of K+ and Cl− in leaves for osmotic adjustment under salt stress. Analysis combining transcriptome and quantitative reverse transcription polymerase chain reaction indicated that compared with that in G. uralensis, the expression of key genes responsible for the biosynthesis of above organic osmolytes, the uptake of NO3−, and the xylem unloading and vacuolar compartmentation of Na+ and NO3− were upregulated in roots of G. inflata under salt stress; meanwhile, higher expression levels of key genes function in xylem loading of K+ and Cl− in roots and vacuolar K+ and Cl− compartmentation in leaves were observed in G. inflata under salt stress. The identified key genes associated with the strong osmotic adjustment capacity of G. inflata could facilitate the genetic improvement of stress tolerance in crops. Core Ideas Glycyrrhiza inflata possesses a stronger salt tolerance than Glycyrrhiza uralensis. G. inflata accumulates higher contents of proline, betaine, and soluble sugar for osmotic adjustment in roots. G. inflata accumulates higher contents of Na+, NO3− in roots, and K+, Cl− in leaves for osmotic adjustment. G. inflata shows induced expression pattern of key genes related to above solute accumulation under salt stress.