Transcriptome Analyses from Mutant Salvia miltiorrhiza Reveals Important Roles for SmGASA4 during Plant Development

Salvia miltiorrhiza (S. miltiorrhiza) is an important Chinese herb that is derived from the perennial plant of Lamiaceae, which has been used to treat neurasthenic insomnia and cardiovascular disease. We produced a mutant S. miltiorrhiza (MT), from breeding experiments, that possessed a large taproot, reduced lateral roots, and defective flowering. We performed transcriptome profiling of wild type (WT) and MT S. miltiorrhiza using second-generation Illumina sequencing to identify differentially expressed genes (DEGs) that could account for these phenotypical differences. Of the DEGs identified, we investigated the role of SmGASA4, the expression of which was down-regulated in MT plants. SmGASA4 was introduced into Arobidopsis and S. militiorrhiza under the control of a CaMV35S promoter to verify its influence on abiotic stress and S. miltiorrhiza secondary metabolism biosynthesis. SmGASA4 was found to promote flower and root development in Arobidopsis. SmGASA4 was also found to be positively regulated by Gibberellin (GA) and significantly enhanced plant resistance to salt, drought, and paclobutrazol (PBZ) stress. SmGASA4 also led to the up-regulation of the genes involved in salvianolic acid biosynthesis, but inhibited the expression of the genes involved in tanshinone biosynthesis. Taken together, our results reveal SmGASA4 as a promising candidate gene to promote S. miltiorrhiza development.