Special Genotypes of ABA Key Functional Genes NCEDs Members in the Glycyrrhizic Acid Synthesis Regulatory Network Promote Glycyrrhizic Acid Synthesis in Licorice

Abstract BackgroundThe glycyrrhizic acid biosynthesis pathway does not exist in isolation, but is connected with the biosynthesis pathways of other secondary metabolites in licorice and finally forms a network. Our previous study found that exogenous spraying of appropriate concentration of abscisic acid (ABA) could increase the content of glycyrrhizic acid (GA) in licorice. However, the mechanism of action remains unknown. We aim to understand the molecular mechanism of ABA promoting the synthesis of GA in licorice and find the molecular marker for the high content of GA germplasm material.MethodsWe analyzed the expression of the key gene of β-AS for GA synthesis after applying ABA, the key functional genes NCED1 , NCED3 and NCED4 in the process of ABA synthesis were overexpression, and analyzed the relationship between the SNP polymorphism of the NCED1 , NCED3 , NCED4 and the content of the GA and ABA in 13 different provenances of licorice with the grey correlation analysis. ResultsThe appropriate concentration of ABA treatment could increase the content of the GA through improving the expression of β-AS . There were significant differences in the content of ABA and GA among the 13 provenances, and the 3 members of the NCEDs family of different provenances had abundant SNP variation sites. Grey correlation and overexpression of NCEDs function both showed that the effect of promoting the synthesis of ABA and GA: NCED1 437 bp G type > NCED3 966 bp G type > NCED4 845 bp A type. All of the above indicated that NCEDs gene variation was the reason for the diversity of GA and ABA content. When selecting high GA germplasm, more priority should be given to NCED1 gene 437 bp G type, NCED3 gene 966 bp G type and NCED4 gene 845 bp A type. ConclusionThis study provides a basis for the selection of excellent GA content germplasm of licorice, and provide some reference for producing a high quality cultivated licorice.