Pengqi Quan

The glucose–methanol–choline (GMC) oxidoreductase superfamily constitutes a crucial group of enzymes involved in diverse physiological processes in insects. However, a systematic investigation of this gene family in the rice leaf roller, Cnaphalocrocis medinalis—a major migratory rice pest—remains lacking. This study identified 54 CmGMC genes in C. medinalis. Genomic analysis revealed its uneven chromosomal distribution, with a conserved 12-gene tandem cluster on chromosome 23. Phylogenetic analysis classified the CmGMC genes into distinct clades, clarifying their evolutionary relationships with GMC homologs in other species. Furthermore, spatiotemporal expression profiling revealed expression of 36 CmGMC genes across all developmental stages and tissues examined, indicating the high transcriptional activity of GMC oxidoreductase genes in C. medinalis. To investigate their role in insecticide response, we examined changes in CmGMC expression following spinetoram treatment. At 48 h post treatment, 20 and 8 genes were significantly upregulated and downregulated, respectively, indicating that specific GMC oxidoreductases may play crucial roles in the molecular response of C. medinalis to spinetoram. This study provides a foundation for understanding the biological functions of GMC oxidoreductases in C. medinalis and reveals their response to the insecticide spinetoram.

Sogatella furcifera (Horváth) is a major migratory rice pest, yet accurate source attribution for this insect remains a persistent challenge. To assess the accuracy of trajectory modeling in determining the source areas of S. furcifera, we examined an early-season migration event into HN in May 2024. Backward trajectories were simulated from 15 sites in HN, and insecticide toxicity assays were conducted to determine LC₅₀ values for pymetrozine and nitenpyram in 26 field populations collected from HN and GX. Trajectory analyses indicated that northwestern HN populations were traced primarily to western GX and northern Vietnam, central HN populations to central/southern GX, western GD, and northern Vietnam, and southeastern HN populations to northeastern/southeastern GX and western GD. Critically, toxicity tests confirmed the trajectory predictions. In particular, no statistically significant differences in LC₅₀ values were detected between HN populations and their identified source areas for either insecticide, while significant differences occurred in comparisons with non-source regions for both insecticides. These findings demonstrate that combining trajectory modeling with toxicity testing effectively identifies S. furcifera source areas during early migration. This study confirms the utility of trajectory analyses and provides an actionable strategy for monitoring and early warning systems targeting migratory pests.

Global warming is posing a threat to animals. As a large group of widely distributed poikilothermal animals, insects are liable to heat stress. How insects deal with heat stress is worth highlighting. Acclimation may improve the heat tolerance of insects, but the underlying mechanism remains vague. In this study, the high temperature of 39 °C was used to select the third instar larvae of the rice leaf folder Cnaphalocrocis medinalis, an important insect pest of rice, for successive generations to establish the heat-acclimated strain (HA39). The molecular mechanism of heat acclimation was explored using this strain. The HA39 larvae showed stronger tolerance to 43 °C than the unacclimated strain (HA27) persistently reared at 27 °C. The HA39 larvae upregulated a glucose dehydrogenase gene, CmGMC10, to decrease the reactive oxygen species (ROS) level and increase the survival rate under heat stress. The HA39 larvae maintained a higher activity of antioxidases than the HA27 when confronted with an exogenous oxidant. Heat acclimation decreased the H₂O₂ level in larvae under heat stress which was associated with the upregulation of CmGMC10. The rice leaf folder larvae may acclimate to global warming via upregulating CmGMC10 to increase the activity of antioxidases and alleviate the oxidative damage of heat stress.