Metabolomic characterization of Pseudomonas protegenssecretions for identification of biopesticides against Bacterial Panicle Blight of rice

Abstract

Bacterial Panicle Blight (BPB) is a rice disease caused by Burkholderia glumae that has become a global concern in reducing rice yields. Currently, there are no effective chemical treatments or resistant cultivars to control BPB. We have observed that bacterial secreted fractions from the antagonistic microorganism Pseudomonas protegens PBL3 inhibits B. glumae infections in rice plants. However, the responsible antimicrobial molecules are unknown. Genome comparison between P. protegens PBL3 and the reference strain P. protegensCHA0, a well‐characterized microbial biological control agent, revealed the presence of 14 known biosynthetic gene clusters (BGCs) in P. protegensPBL3. From this genomic data, it is likely that P. protegensPBL3 secretes metabolites with activity against BPB that are not produced by P. protegensCHA0.Cultures of P. protegensPBL3 and the reference strain, P. protegensCHA0, were grown in M9 minimal media supplemented with 1% myo‐inositol. The metabolite secretome of P. protegens PBL3 and CHA0 were harvested in log phase and analyzed with a Waters Acquity H‐Class HPLC coupled to a Thermo Q‐Exactive HF‐X. In addition, active PBL3 fractions against B. glumaewere analyzed via LC‐MS to confirm the presence of bioactive compounds. The resulting data were searched against the Global Natural Products Social Molecular Networking (GNPS) spectral library. For potential antimicrobial peptide identification, data were searched against the Mascot database. To validate these results, known bioactive metabolites in P. protegensCHA0 were identified. By utilizing LC‐MS/MS based metabolomics, several compounds were uniquely identified in P. protegensPBL3 that could be used as biocontrol agents against BPB in rice.