Root rot disease caused by Fusarium oxysporum is a devastating disease of Salvia miltiorrhiza and dramatically affected the production and quality of Sa. miltiorrhiza. Besides the agricultural and chemical control, biocontrol agents can be utilized as an additional solution. In the present study, an actinomycete that highly inhibited F. oxysporum was isolated from rhizosphere soil and identified as based on morphological and molecular characteristics. Greenhouse assay proved that the strain had significant biological control effect against Sa. miltiorrhiza root rot disease and growth-promoting properties on Sa. miltiorrhiza seedlings. To elucidate the biocontrol and plant growth-promoting properties of St-220, we employed an analysis combining genome mining and metabolites detection. Our analyses based on genome sequence and bioassays revealed that the inhibitory activity of St-220 against F. oxysporum was associated with the production of enzymes targeting fungal cell wall and metabolites with antifungal activities. Strain St-220 possesses phosphate solubilization activity, nitrogen fixation activity, siderophore and indole-3-acetic acid production activity in vitro, which may promote the growth of Sa. miltiorrhiza seedlings. These results suggest that St. albidoflavus St-220 is a promising biocontrol agent and also a biofertilizer that could be used in the production of Sa. miltiorrhiza.

Introduction: Puerariae thomsonii Benth is an important medicinal and edible plant, with its dried roots being widely used in traditional Chinese medicine. The secondary metabolites of P. thomsonii mainly contain flavonoid compounds that have beneficial effects on human health. Current researches on the secondary metabolites of P. thomsonii have primarily focused on the effects of external environmental factors, while studies investigating the impact of internal microorganisms on its secondary metabolites remain limited.Methods: In this study, P. thomsonii roots were collected from five different regions in Jiangxi province to investigate the diversity of endophytic bacteria and their correlation with five isoflavones (puerarin, daidzin, genistin, daidzein, and genistein). The differences between endophytes and the content of five isoflavones were analyzed using high-throughput sequencing and UPLC methods. In addition, differences in endophytic bacteria across the samples from different productions were analyzed using LEfSe analysis. The functional capabilities of these bacteria were analyzed through PICRUSt2 to explore potential microbial functional traits.Results: The findings indicated that the alpha diversity of endophytic bacteria in P. thomsonii differed among production areas and the unique bacterial genera could be found in different areas. Four secondary metabolites in P. thomsonii were found to have a positive correlation with the diversity, evenness, and richness of endophytic bacterial communities using Spearman’s correlation analysis. Genera such as unclassified_f_ Xanthomonadaceae, Bosea, and Methylobacterium–Methylorubrum were significant positively correlated with one or more of these secondary metabolites.Discussion: This research enriches the endophytic bacterial resources of P. thomsonii, provides a preliminary analysis of the correlation between plants and microorganisms, and offers a scientific basis for the future exploration and application of endophytic resources in P. thomsonii.

LuxR-type transcriptional regulators are essential for many physiological processes in bacteria, including pathogenesis. Acidovorax citrulli is a seedborne bacterial pathogen responsible for bacterial fruit blotch, which causes great losses in melon and watermelon worldwide. However, the LuxR-type transcriptional factors in A. citrulli have not been well studied, except for the previously reported LuxR-type regulatory protein, AcrR, involved in regulating virulence and motility. Here, we characterized a second LuxR-type regulator, AclR, in the group II strain Aac-5 of A. citrulli by mutagenesis, virulence and motility assays, and transcriptomic analysis. Deletion of aclR resulted in impaired twitching and swimming motility and flagellar formation and diminished virulence but increased biofilm formation. Transcriptomic analysis revealed that 1,379 genes were differentially expressed in the aclR mutant strain, including 29 genes involved in flagellar assembly and 3 involved in pili formation, suggesting a regulatory role for AclR in multiple important biological functions of A. citrulli. Together, our results not only indicate that AclR plays a global role in transcriptional regulation in A. citrulli influencing motility, biofilm formation, and virulence but also provide perspective regarding the regulatory network of biological functions in A. citrulli. [ ] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

Dendrobe (Dendrobium spp.) is a traditional medicinal and edible food, which is rich in nutrients and contains biologically active metabolites. The quality and price of dendrobe are related to its geographical origins, and high quality dendrobe is often imitated by low quality dendrobe in the market. In this work, near-infrared (NIR) spectroscopy sensor combined with porphyrin and chemometrics was used to distinguish 360 dendrobe samples from twelve different geographical origins. Partial least squares discriminant analysis (PLSDA) was used to study the sensing performance of traditional NIR and tera-(4-methoxyphenyl)-porphyrin (TMPP)-NIR on the identification of dendrobe origin. In the PLSDA model, the recognition rate of the training and prediction set of the TMPP-NIR could reach 100%, which was higher than the 91.85% and 91.34% of traditional NIR. And the accuracy, sensitivity, and specificity of the TMPP-NIR sensor are all 1.00. The mechanism of TMPP improving the specificity of NIR spectroscopy should be related to the π-π conjugated system and the methoxy groups of TMPP interact with the chemical components of dendrobe. This study reflected that NIR spectrum with TMPP sensor was an effective approach for identifying the geographic origin of dendrobe.