Transcriptome sequencing and ITRAQ reveal the detoxification mechanism of Bacillus GJ1, a potential biocontrol agent for Huanglongbing

PLoS One. 2018 Aug 9;13(8):e0200427. doi: 10.1371/journal.pone.0200427. eCollection 2018.

Abstract

Huanglongbing (HLB) is the most serious disease affecting citrus production worldwide. No HLB-resistant citrus varieties exist. The HLB pathogen Candidatus Liberibacter asiaticus is nonculturable, increasing the difficulty of preventing and curing the disease. We successfully screened the biocontrol agent Bacillus GJ1 for the control of HLB in nursery-grown citrus plants. RNA sequencing (RNA-seq) of the transcriptome and isobaric tags for relative and absolute quantification of the proteome revealed differences in the detoxification responses of Bacillus GJ1-treated and -untreated Ca. L. asiaticus-infected citrus. Phylogenetic tree alignment showed that GJ1 was classified as B. amyloliquefaciens. The effect of eliminating the HLB pathogen was measured using real-time quantitative polymerase chain reaction (qPCR) and PCR. The results indicate that the rate of detoxification reached 50% after seven irrigations, of plants with an OD600nm≈1 Bacillus GJ1 suspension. Most importantly, photosynthesis-antenna proteins, photosynthesis, plant-pathogen interactions, and protein processing in the endoplasmic reticulum were significantly upregulated (padj < 0.05), as shown by the KEGG enrichment analysis of the transcriptomes; nine of the upregulated genes were validated by qPCR. Transcription factor analysis of the transcriptomes was performed, and 10 TFs were validated by qPCR. Cyanoamino acid metabolism, regulation of autophagy, isoflavonoid biosynthesis, starch and sucrose metabolism, protein export, porphyrin and chlorophyll metabolism, and carotenoid biosynthesis were investigated by KEGG enrichment analysis of the proteome, and significant differences were found in the expression of the genes involved in those pathways. Correlation analysis of the proteome and transcriptome showed common entries for the significantly different expression of proteins and the significantly different expression of genes in the GO and KEGG pathways, respectively. The above results reveal important information about the detoxification pathways.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacillus / physiology*
  • Bacterial Proteins / genetics*
  • Bacterial Proteins / metabolism*
  • Citrus / microbiology*
  • Host-Pathogen Interactions
  • Isotope Labeling
  • Mass Spectrometry
  • Plant Diseases / microbiology
  • Plant Diseases / prevention & control*
  • Plant Leaves
  • Proteome*
  • Transcriptome*

Substances

  • Bacterial Proteins
  • Proteome

Grants and funding

Funding for this research was provided by The "Nation Nature Science Funding" (grant numbers 31572099 and31272146). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.