Symbiont Gene Expression Predicts Insect Host's Response to High Temperatures

Area of Science:

• Microbial Ecology
• Symbiosis Research
• Insect-Microbe Interactions

Background:

• Microbial symbionts are vital for host health, providing nutrition, defense, and detoxification.
• Environmental stressors, particularly thermal stress, can disrupt host-symbiont relationships, negatively impacting host performance.
• Previous studies show thermal stress affects symbionts, leading to host vulnerability, but the mechanisms driving variation in host outcomes remain unclear.

Purpose of the Study:

• To investigate the mechanisms underlying variable insect performance at elevated temperatures based on hosted symbiont species.
• To compare host and symbiont transcriptional responses to thermal stress in a bug-Caballeronia model system.
• To test if symbionts conferring better host outcomes under heat stress exhibit enhanced heat shock gene regulation.

Main Methods:

• Comparative metatranscriptomics was employed to analyze gene expression in both host insects and their symbionts.
• Two symbiont species with contrasting effects on host performance at high temperatures were utilized.
• Transcriptional responses of both host and symbiont were evaluated under varying temperature conditions.

Main Results:

• Host transcriptional patterns were primarily influenced by temperature, not by the specific symbiont species present.
• Distinct gene expression profiles were observed between symbionts across different temperatures.
• The heat-resistant symbiont upregulated heat shock genes and unexpectedly activated flagellar genes at 36°C, a departure from typical symbiotic gene expression.

Conclusions:

• Symbiont transcriptional regulation, rather than host transcription, is the primary driver of host benefits under varying temperatures.
• The findings highlight the critical role of symbiont responses in mediating host performance during environmental stress.
• This research deepens the understanding of context-dependent outcomes in symbiotic associations and their resilience to climate change.