[De novo sequencing and analysis of root transcriptome to reveal regulation of gene expression by moderate drought stress in Glycyrrhiza uralensis].

Moderate drought stress has been found to promote the accumulation of active ingredients in Glycyrrhiza uralensis root and hence improve the medicinal quality. In this study, the transcriptomes of 6-month-old moderate drought stressed and control G. uralensis root (the relative water content in soil was 40%-45% and 70%-75%, respectively) were sequenced using Illumina HiSeq 2000. A total of 80,490 490 and 82 588 278 clean reads, 94,828 and 305,100 unigenes with N50 sequence of 1,007 and 1,125 nt were obtained in drought treated and control transcriptome, respectively. Differentially expressed genes analysis revealed that the genes of some cell wall enzymes such as ß-xylosidase, legumain and GDP-L-fucose synthase were down-regulated indicating that moderate drought stress might inhibit the primary cell wall degradation and programmed cell death in root cells. The genes of some key enzymes involved in terpenoid and flavonoid biosynthesis were up-regulated by moderate drought stress might be the reason for the enhancement for the active ingredients accumulation in G. uralensis root. The promotion of the biosynthesis and signal transduction of auxin, ethylene and cytokinins by moderate drought stress might enhance the root formation and cell proliferation. The promotion of the biosynthesis and signal transduction of abscisic acid and jasmonic acid by moderate drought stress might enhance the drought stress tolerance in G. uralensis. The inhibition of the biosynthesis and signal transduction of gibberellin and brassinolide by moderate drought stress might retard the shoot growth in G. uralensis.