Microbial Communities in Different Developmental Stages of the Oriental Fruit Fly, Bactrocera dorsalis, Are Associated with Differentially Expressed Peptidoglycan Recognition Protein-Encoding Genes

Abstract

The insect microbiota can change dramatically to enable adaptation of the host in different developmental stages and environments; however, little is known about how the host maintains its microbiota to achieve such adaptations. In this study, 16S rRNA sequencing revealed that the microorganisms in larvae and adults of the Oriental fruit fly, Bactrocera dorsalis, are primarily Gram-negative bacteria but that the major components in pupae are Gram-positive bacteria. Using suppression subtractive hybridization (SSH) and transcriptome analysis, we screened two specifically expressed genes encoding peptidoglycan recognition proteins (PGRP-LB and PGRP-SB1) and analyzed their relationship to B. dorsalis microbial communities. Knockdown of the PGRP-LB gene in larvae and adults led to increased ratios of Gram-positive bacteria; knockdown of the PGRP-SB1 gene in pupae led to increased ratios of Gram-negative bacteria. Our results suggest that maintenance of the microbiota in different developmental stages of B. dorsalis may be associated with the PGRP-LB and PGRP-SB1 genes.IMPORTANCE Microorganisms are ubiquitous in insects and have widespread impacts on multiple aspects of insect biology. However, the microorganisms present in insects can change dramatically in different developmental stages, and it is critical to maintain the appropriate microorganisms in specific host developmental stages. Therefore, analysis of the factors associated with the microbiota in specific development stages of the host is needed. In this study, we applied suppression subtractive hybridization (SSH) combined with transcriptome analysis to investigate whether the microbiota in development stages of the Oriental fruit fly, Bactrocera dorsalis, is associated with expression of PGRP genes. We found that two different PGRP genes were specifically expressed during development and that these genes may be associated with changes in microbial communities in different developmental stages of B. dorsalis.

Keywords: Bactrocera dorsalis; association; developmental stages; immune-related genes; microbiota.

FIG 1

Comparison of the microbiotal structure in different developmental stages of B. dorsalis. (a) Percentages of bacterial phyla in different samples. Only phyla with a relative abundance greater than 2% are shown. (b) Percentages of Gram-positive and Gram-negative bacterial phyla in different samples. (c) LEfSe analysis based on OTU abundance in different development stages. (d) PCoA plot based on the microbiotal structure in different developmental stages. L, larva; P, pupa; A, adult.

FIG 2

Relative expression of PGRP-LB and PGRP-SB1 genes. (a) Relative expression of PGRP-LB and PGRP-SB1 genes during different developmental stages. (b) Effects of RNAi interference of PGRP-LB and PGRP-SB1. The statistical comparison was based on one-way analysis of variance (different letters indicate significant difference) or the independent-sample t test (*, P < 0.05; **, P < 0.01). M, male; F, female; CK, control.

FIG 3

Comparison of the microbiotal structure between RNAi and control larva samples. (a) Percentage of bacterial phyla in the RNAi and control groups. Only phyla with a relative abundance greater than 2% are shown. (b) Percentages of Gram-positive and Gram-negative bacteria in RNAi and control larvae. (c) LEfSe analysis based on OTU abundance in RNAi and control larvae. (d) PCoA plot based on the microbiotal structure in different treatments.

FIG 4

Comparison of the microbiotal structure between RNAi and control adult samples. (a) Percentages of bacterial phyla in the RNAi treatment and control groups. Only phyla with a relative abundance greater than 2% are shown. (b) Percentage of Gram-positive and Gram-negative bacteria in RNAi and control adults. (c) LEfSe analysis based on OTU abundance in RNAi and control adults. (d) PCoA plot based on the microbiotal structure in different treatments.

FIG 5

Comparison of the microbiotal structure between RNAi and control pupa samples. (a) Percentages of bacterial phyla in the RNAi treatment and control groups. Only taxonomic units with a relative abundance greater than 2% are shown. (b) Percentages of Gram-positive and Gram-negative bacteria between RNAi and control pupae. (c) LEfSe analysis based on OTU abundance in RNAi and control pupae. (d) PCoA plot based on the microbiotal structure in different treatments.