Multi-omics profiling reveals antagonistic strategies of endophytic Streptomyces sp. MEPP0209 against Lasiodiplodia theobromae causing Dendrobium officinale stem rot.
TL;DR
Metabolomics analysis and in vitro antagonistic assays indicated that the candidate antagonistic substances, 5,6-dimethylbenzimidazole and pyrrole-2-carboxylic acid, can effectively inhibit the growth of L. theobromae.
Abstract
Stem rot disease frequently occurs during the artificial cultivation of Dendrobium officinale Kimura et Migo, which has adverse effects on its yield and quality. Endophytic bacteria present in plants represented potential sources of biocontrol agents. This study isolated 43 distinct microbial strains from wild Dendrobium moniliforme (L.) Sw., among which strain MEPP0209 exhibited significant inhibition of Lasiodiplodia theobromae hyphal growth. Based on the 16S rDNA sequences, the strain was identified as Streptomyces sp. MEPP0209. The cell-free supernatant (CFS) of MEPP0209 significantly inhibited L. theobromae growth, and effectively reduced the disease index of stem rot in D. officinale tissue-cultured seedlings. Transcriptome analysis showed that differentially expressed genes (DEGs) related to cell division and cell cycle were significantly downregulated in L. theobromae hyphae after MEPP0209 CFS treatment, such as MCM2/3/4/5/6/7, NDT80, POLA1, and MBP1, while DEGs related to energy metabolism and oxidative stress were significantly upregulated. Metabolomics analysis and in vitro antagonistic assays indicated that the candidate antagonistic substances, 5,6-dimethylbenzimidazole and pyrrole-2-carboxylic acid, can effectively inhibit the growth of L. theobromae. And qRT-PCR results obtained from the pathogen treated with these two metabolites further indicated the downregulation of genes implicated in cell division and cell cycle. Overall, our findings suggested that the inhibition of fungal growth by MEPP0209 may be associated with the downregulation of genes related to cell division and proliferation in L. theobromae. The metabolites produced by MEPP0209, including 5,6-dimethylbenzimidazole and pyrrole-2-carboxylic acid, likely contributed to this inhibitory effect. This study provides a theoretical basis for future investigations into the role of MEPP0209 in biological control of D. officinale stem rot.