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 NO 3 − 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 NO 3 − , and the xylem unloading and vacuolar compartmentation of Na + and NO 3 − 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. Abbreviations: AKT, inwardly rectifying K + channel; AMS, amylase; BADH, betaine aldehyde dehydrogenase; CCX, cation/Ca 2+ exchanger; CHX, cation/H + exchanger; CLC, Cl − channel; CMO, choline monooxygenase; GDH, glutamate dehydrogenase; GOGAT, glutamate synthase; HKT, high-affinity K + transporter; KT/HAK/KUP, K + transporter; MD, mannitol dehydrogenase; NHX, tonoplast Na + /H + antiporter; NRT, NO 3 − transporter; P5CS, Δ1 -pyrroline-5-carboxylate synthetase; PEAMT, phosphoethanolamine N-methyltransferase; qRT-PCR, quantitative reverse transcription polymerase chain reaction; SKOR, stelar K + outwardly rectifying channel; SLAH, slow type anion channel; SPS, sucrose-phosphate synthase; SS, starch synthase.
