Coordination of host and endosymbiont gene expression governs endosymbiont growth and elimination in the cereal weevilSitophilusspp

Abstract

Insects living in nutritionally poor environments often establish long-term relationships with intracellular bacteria that supplement their diets and improve their adaptive and invasive powers. Even though these symbiotic associations have been extensively studied on physiological, ecological and evolutionary levels, few studies have focused on the molecular dialogue between host and endosymbionts to identify genes and pathways involved in endosymbiosis control and dynamics. We simultaneously analyzed host and endosymbiont gene expression during the life cycle of the cereal weevilSitophilus oryzae, from larval stages to adults, with a particular emphasis on emerging adults where the endosymbiontSodalis pierantoniusexperiences a contrasted growth-climax-elimination dynamics. We unraveled a constant arms race in which different biological functions are intertwined and coregulated across both partners. These include immunity, metabolism, metal control, apoptosis, and bacterial stress response. Particularly, genes from the Hippo regulatory pathway are specifically induced by endosymbiont growth, while the regulation of metal ions constitutes the basis of the arms race between the two partners at the onset of the bacterial load climax. The study of these tightly regulated functions, which are at the center of symbiotic regulations, provides evidence on how hosts and bacteria finely tune their gene expression and respond to different physiological challenges constrained by insect development in a nutritionally limited ecological niche.

Transcriptomic-based selection of reference genes for quantitative real-time PCR in an insect endosymbiotic model

“…RNAseq datasets were processed in our previous publication (Ferrarini et al, 2023), and raw reads are available at BioProject PRJNA918957. Briefly, quality check was performed with FastQC v0.11.8 (Andrews, 2010), and raw reads were quality trimmed using trim_galore from Cutadapt v0.6.7 (Martin, 2011), then mapped to the S. oryzae's genome (GCA_002938485.2 Soryzae_2.0) using STAR v2.7.3a (Dobin et al, 2013).…”

“…Then, uniquely mapping reads were counted with featureCounts v2.0.1 (Liao et al, 2014), and mapping quality was assessed by multiqc v1.13 (Ewels et al, 2016). Differential expression analysis was conducted with SarTOOLS, taking advantage of a global linear model from Deseq2 (Love et al, 2014, 2), and log2 fold changes and adjusted p-values were obtained for sequential pairwise comparisons, i.e., L4 vs. D1, D1 vs. D3 etc., 10.3389/fevo.2023.1152183 and can be found in the Supplementary material of our previous report (Ferrarini et al, 2023). Most graphic outputs are either performed in R, using ggplot2 (Wickham, 2009) or with GraphPad Prism software.…”

“…L4: larval stage 4; P: pupae; D1: 1-day-old adults; D3: 3-day-old adults; D5: 5-day-old adults; D7: 7-day-old adults; D9: 9-day-old adults. Data represent normalized counts at each developmental stage (Ferrarini et al, 2023). Error bars represent standard deviation.…”

“…Analyzing transcriptomic regulations across weevil's development is required to fully understand S. oryzae and S. pierantonius relationship, and to uncover key pathways profitable for integrative pest management strategies. We have recently conducted a thorough analysis of the gut (and associated bacteriomes) transcriptome of S. oryzae across its development from larval stages up to bacterial clearance in adults (Figure 1; Ferrarini et al, 2023). In this work, we took advantage of the recent transcriptomic profile of S. oryzae during development (Ferrarini et al, 2023) to select a set of reliable reference genes for qRT-PCR analyses, with high stability and conservation among insects.…”

“…We have recently conducted a thorough analysis of the gut (and associated bacteriomes) transcriptome of S. oryzae across its development from larval stages up to bacterial clearance in adults (Figure 1; Ferrarini et al, 2023). In this work, we took advantage of the recent transcriptomic profile of S. oryzae during development (Ferrarini et al, 2023) to select a set of reliable reference genes for qRT-PCR analyses, with high stability and conservation among insects. The identified transcripts will be of use for the comparison of transcript abundance across multiple developmental stages in S. oryzae, gene silencing conditions, and comparisons with artificially obtained aposymbiotic weevils.…”