Genome-Wide Identification and Expression Analysis of Sucrose Nonfermenting 1-Related Protein Kinase (SnRK) Genes in Salvia miltiorrhiza in Response to Hormone

The SnRK gene family is the chief component of plant stress resistance and metabolism through activating the phosphorylation of downstream proteins. S. miltiorrhiza is widely used for the treatment of cardiovascular diseases in Asian countries. However, information about the SnRK gene family of S. miltiorrhiza is not clear. The aim of this study is to comprehensively analyze the SnRK gene family of S. miltiorrhiza and its response to phytohormone. Here, 33 SmSnRK genes were identified and divided into three subfamilies (SmSnRK1, SmSnRK2 and SmSnRK3) according to phylogenetic analysis and domain. SmSnRK genes within same subgroup shared similar protein motif composition and were unevenly distributed on eight chromosomes of S. miltiorrhiza. Cis-acting element analysis showed that the promoter of SmSnRK genes was enriched with ABRE motifs. Expression pattern analysis revealed that SmSnRK genes were preferentially expressed in leaves and roots. Most SmSnRK genes were induced by ABA and MeJA treatment. Correlation analysis showed that SmSnRK3.15 and SmSnRK3.18 might positively regulate tanshinone biosynthesis; SmSnRK3.10 and SmSnRK3.12 might positively regulate salvianolic acid biosynthesis. RNAi-based silencing of SmSnRK2.6 down-regulated the biosynthesis of tanshinones and biosynthetic genes expression. An in vitro phosphorylation assay verified that SmSnRK2.2 interacted with and phosphorylated SmAREB1. These findings will provide a valuable basis for the functional characterization of SmSnRK genes and quality improvement of S. miltiorrhiza.

The SmERF1b-like regulates tanshinone biosynthesis in Salvia miltiorrhiza hairy root

The ethylene response factor family genes are involved in the regulation of secondary metabolism in Salvia miltiorrhiza, but the mechanism underlying this regulation remains elusive. In the present study, based on the cDNA library of S. miltiorrhiza, an AP2/ERF gene was cloned and named SmERF1b-like. This gene exhibited a significant response to exogenous ethylene supply, such that ethylene remarkably upregulated SmERF1b-like expression levels in the leaves of S. miltiorrhiza. Subcellular localization showed that SmERF1b-like is located in the nucleus. Furthermore, SmERF1b-like showed a binding affinity with a GCC-box motif in the promoter region of genes associated with tanshinone biosynthesis in S. miltiorrhiza. Overexpression of SmERF1b-like in hairy roots of S. miltiorrhiza substantially upregulated SmCPS1 and SmKSL1 expression levels, resulting in increased biosynthesis of tanshinone I and cryptotanshinone contents. This finding provides valuable theoretical support for the utilization of a plant genetic engineering strategy to enhance S. miltiorrhiza resources.

Traditional Chinese medicine residues promote the growth and quality of Salvia miltiorrhiza Bunge by improving soil health under continuous monoculture

Continuous monoculture of crops has resulted in reduced yields and quality, as well as soil deterioration. Although traditional Chinese medicine residues (TCMRs) are known to promote plant growth and soil health, few studies have investigated their effectiveness in continuous monoculture soils. Here, we studied the impact of chemical fertilizers (CF) and four TCMRs with antibacterial activities on the growth of S. miltiorrhiza (a widely used medicinal plant in China), accumulation of active ingredients in plants, and soil health under continuous monoculture conditions. Compared with no fertilizer (CK) and CF, fermented Sophora flavescens radix residue (SFRf) and fermented and unfermented Moutan cortex residue (MCRf and MCRu, respectively) resulted in a reduction of the disease index of root rot, while CF did not. The CF and four TCMR treatments increased the accumulation of nitrogen (N) (42.8-124.6% and 17.0-101.7%), phosphorous (P) (19.8-74.7% and 8.3-27.4%), and potassium (K) (104.1-212.0% and 9.3-51.8%) in shoots and roots compared to CK. The differences in nutrient accumulation between the CF and TCMR treatments were statistically insignificant, excepted for the N accumulation in the roots. All fertilization treatments increased plant biomass compared to CK, with increases of 25.57-89.86% and 2.62-35.28% in shoots and roots, respectively. The SFRf treatment exhibited the most significant enhancement in both shoot and root biomass. CF significantly reduced the accumulation of seven active ingredients in roots by 23.90-78.95% compared to CK, whereas each TCMR increased accumulation of certain active ingredients. The TCMR treatments effectively improved the health of deteriorated soil by enhancing soil physicochemical properties, restoring the balance of the microbial community, recruiting beneficial bacteria, and reducing the relative abundance of the pathogen Fusarium. The SFRf treatment exhibited superior performance in improving soil health than other treatments. Overall, the TCMRs outperformed CF in restoring soil health and promoting the yield and quality of S. miltiorrhiza. These findings offer guidance for improving the health of continuous cropping soil and recycling TCMRs.

Effects of cadmium on the synthesis of active ingredients in Salvia miltiorrhiza

Cadmium (Cd) could pose threats to human health by affecting Salvia miltiorrhiza (SM) safety. Cd enrichment trait and its effects on the active ingredient synthesis in SM remain unknown. Here we investigated the Cd concentration using ICP-MS-based method, physiologies (contents of malondialdehyde and proline, and activities of superoxide dismutase, peroxidase [POD], and catalase [CAT]), and LC-MS/MS-based metabolites of SM under 25, 50, and 100 mg kg^-1 Cd stress. The results revealed that Cd concentrations, as it rose in soil, increased in roots and leaves of SM with transfer factors and bioconcentration factors below 1 in Cd-treated groups; POD and CAT activities and proline content increased and then declined. Amino acids and organic acids (especially d-glutamine [d-Gln], l-aspartic acid [l-Asp], l-phenylalanine [l-Phe], l-tyrosine [l-Tyr], geranylgeranyl-PP [GGPP], and rosmarinic acid [RA]) contributed more in discriminating SM roots of different groups. GGPP was negatively related to l-Tyr and l-Phe, and RA was positively related to d-Gln and l-Asp in SM. These results revealed that SM belonged to a non-Cd-hyperaccumulator with most Cd accumulated in roots, Cd could enhance phenolic acid synthesis via regulating amino acid metabolism and might inhibit tanshinone synthesis by declining the GGPP content, and proline, POD, and CAT played vital roles in resisting Cd stress. These provided new ideas and theoretical basis for further study on medical plants' response to heavy metals.

The complete chloroplast genome sequence of Salvia miltiorrhiza, a medicinal plant for preventing and treating vascular dementia

S. miltiorrhiza is a perennial herb of the genus Salvia (Lamiaceae), which is an important medicinal plant for preventing and treating vascular dementia. The complete chloroplast genome sequence of Salvia miltiorrhiza was characterized from Illumina pair-end sequencing. The chloroplast genome of S. miltiorrhiza was 152,680 bp in length, containing a large single-copy region (LSC) of 84,104 bp, a small single-copy region (SSC) of 17,638 bp, and two inverted repeat (IR) regions of 25,469 bp. The overall GC content is 38.70%, while the correponding values of the LSC, SSC, and IR regions are 36.2%, 31.9%, and 43.2%, respectively. The genome contains 131 complete genes, including 86 protein-coding genes (62 protein-coding gene species), 37 tRNA genes (29 tRNA species) and 8 rRNA genes (4 rRNA species). The Neighbour-joining phylogenetic analysis showed that S. miltiorrhiza and Salvia przewalskii clustered together as sisters to other Salvia species.

Systematic Analysis of Kelch Repeat F-box (KFB) Protein Gene Family and Identification of Phenolic Acid Regulation Members in Salvia miltiorrhiza Bunge

S. miltiorrhiza is a well-known Chinese herb for the clinical treatment of cardiovascular and cerebrovascular diseases. Tanshinones and phenolic acids are the major secondary metabolites and significant pharmacological constituents of this plant. Kelch repeat F-box (KFB) proteins play important roles in plant secondary metabolism, but their regulation mechanism in S. miltiorrhiza has not been characterized. In this study, we systematically characterized the S. miltiorrhiza KFB gene family. In total, 31 SmKFB genes were isolated from S. miltiorrhiza. Phylogenetic analysis of those SmKFBs indicated that 31 SmKFBs can be divided into four groups. Thereinto, five SmKFBs (SmKFB1, 2, 3, 5, and 28) shared high homology with other plant KFBs which have been described to be regulators of secondary metabolism. The expression profile of SmKFBs under methyl jasmonate (MeJA) treatment deciphered that six SmKFBs (SmKFB1, 2, 5, 6, 11, and 15) were significantly downregulated, and two SmKFBs (SmKFB22 and 31) were significantly upregulated. Tissue-specific expression analysis found that four SmKFBs (SmKFB4, 11, 16, and 17) were expressed preferentially in aerial tissues, while two SmKFBs (SmKFB5, 25) were predominantly expressed in roots. Through a systematic analysis, we speculated that SmKFB1, 2, and 5 are potentially involved in phenolic acids biosynthesis.

The ethylene response factor SmERF8 regulates the expression of SmKSL1 and is involved in tanshinone biosynthesis in Saliva miltiorrhiza hairy roots

Saliva miltiorrhiza ethylene response factor (SmERF), predicted to be expressed genome-wide, is the potential regulator of tanshinone biosynthesis. However, few studies have investigated its transcriptional regulation pathways in tanshinone biosynthesis. Here, we report an ethylene response factor (SmERF8), which was screened by the SmKSL1 (a key gene in tanshinone biosynthesis) promoter from the S. miltiorrhiza cDNA library. The SmERF8, highly expressed in S. miltiorrhiza root head, is sensitive to Eth stress, and its protein was enriched in the nucleus. The SmERF8 recognizes the GCC-box in the SmKSL1 promoter. Overexpression and RNAi of SmERF8 in S. miltiorrhiza transgenic hairy roots showed that the tanshinone contents were significantly increased in the overexpression transgenic lines and decreased in RNAi lines. These results suggest that the SmERF8 may be a central activator that regulates the expression of SmKSL1 by binding the GCC-box and then promoting tanshinone biosynthesis. Thus, the SmERF8 may functionally accelerate tanshinone biosynthesis by the transcriptional regulation of its key gene.