Physiological and transcriptomic insights into root response patterns of Glycyrrhiza uralensis under drought and salt stress

Drought and soil salinization restrict the yield and quality of Glycyrrhiza uralensis Fisch. In this study, PEG was applied to simulate drought treatment and sodium chloride was used to simulate salt stress, with conventional nutrient conditions serving as the control group. We measured seven physiological indicators related to the stress and conducted Illumina HiSeq transcriptome sequencing analysis of the roots. Both stress treatments reduced the relative water content and chlorophyll content of the leaves, while increasing the contents of proline, soluble sugar, MDA, as well as SOD and POD activities; and the damage characteristics caused by drought stress and salt stress were significantly different. A large number of differentially expressed genes were identified through transcriptome analysis, and 258 common differentially expressed genes screened from the database were regarded as core stress response genes. These genes were significantly enriched in the biosynthesis of phenylpropanoids and flavonoids, hormone and MAPK signal transduction pathways. The expression levels of multiple transcription factor families changed significantly, and GuWRKY33 was strongly induced in both stress conditions. The reliability of transcriptome data was verified by qR-TPCR experiments. This study presents the transcriptomic characteristics and provides a theoretical basis and genetic resources for exploring the molecular mechanism of its stress resistance and for cultivating stress-resistant varieties.