Detoxification Responses of Tuta absoluta (Meyrick) to Serratia marcescens (Bizio) Strain Tapa21 Infection Revealed by Transcriptomics

Tuta absoluta (Meyrick) is a globally invasive lepidopteran pest that has developed resistance to multiple classes of chemical insecticides, posing major challenges for the sustainable production of Solanaceae crops. In this study, we investigated the physiological and molecular responses of T. absoluta larvae to infection by the entomopathogenic bacterium Serratia marcescens (Bizio) strain Tapa21, which was isolated from naturally infected larvae and characterized through phenotypic, molecular, and phylogenetic analyses. Laboratory bioassays demonstrated dose- and time-dependent mortality of T. absoluta larvae, with mortality reaching nearly 80% at the highest Tapa21 concentration at 120 h post-infection (hpi), with a median lethal concentration (LC50) of Optical Density (OD)600 = 0.52 and a median lethal time (LT50) of 5.2 d. RNA-Seq was performed, revealing 493 differentially expressed genes (DEGs), including 304 up-regulated and 189 down-regulated transcripts. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses indicated activation of detoxification-related enzymes, lysosome- and immune-associated pathways, and metabolic reprogramming, suggesting coordinated defense responses. A subset of genes, randomly selected across expression levels, was validated by RT-qPCR, corroborating the transcriptomic results. These results delineate the molecular mechanisms by which T. absoluta reshapes its physiological state during bacterial challenge and provide insight into how entomopathogenic strain Tapa21 disrupts host homeostasis. Such a mechanistic understanding could potentially contribute to sustainable and integrated pest management (IPM) strategies.