Metabolic responses reveal insight into interspecific variation in heat tolerance of three co-existing pest aphid species

Global warming leads to an increase in extreme heat events, posing significant challenges for insects. Sitobion avenae, Metopolophium dirhodum, and Rhopalosiphum padi are important co-existing aphid species known to cause damage to cereal crops worldwide. The three species differ in thermal tolerance, with R. padi being much more heat tolerant than the other two species. However, it remains unclear whether interspecific variation in heat tolerance is due to differences in metabolic responses to heat stress. Here, we compared their metabolic signatures during and after recovery from the same injury level of heat stress (at 34°C for half and full durations to cause 50% mortality in each species), as well as the identical duration of heat stress. Using quantitative GC-MS, we found that after the same injury level of heat exposure, the three species showed similar changes in most metabolites. However, the heat-tolerant species, R. padi, had higher levels of polyols and amino acids, and uniquely accumulated glycerol. In addition, after the same duration of heat exposure, R. padi maintained a relatively stable metabolic profile, while the less tolerant species showed marked alterations with shift from aerobic to anaerobic metabolism. We suggest that polyols and amino acids play a pivotal role in protecting R. padi from heat damage, conferring its superior thermal tolerance. Overall, this comparative metabolomics study provides insight into the relationship between metabolic responses and heat tolerance of co-existing species, which helps to understand the underlying mechanism of heat tolerance.