Transcriptomic analysis of oriental tea tortrix infected with male-killing virus

Male-killing is a reproductive manipulation in which males die at specific developmental stages. Although most known cases are caused by maternally inherited bacteria, recent studies have shown that symbiotic viruses can also induce male-specific lethality. In the tea tortrix moth Homona magnanima, Osugoroshi virus 1‒3 (OGVs; family Partitiviridae) cause male-killing during the larval stage, with infected males exhibiting molting arrest prior to death. Previous work demonstrated OGV-induced male-killing differs mechanistically from that of bacterial symbionts such as Wolbachia and Spiroplasma; however, the underlying molecular basis remains unclear. This study aimed to elucidate the transcriptional and endocrine changes associated with OGV-induced male mortality.

We performed comparative RNA sequencing of second-instar larvae from normal sex ratio and OGV-infected lines of H. magnanima, focusing on males at the molting stage (the second larval instar, day 2; hereafter L2D2) and the molting-arrested stage (day 6; L2D6). Differential expression and KEGG enrichment analyses revealed male-specific upregulation of Toll/Imd and epidermal growth factor receptor signaling pathways and downregulation of metabolism-related genes. Analysis of liquid chromatography-tandem mass spectrometry detected persistent 20-hydroxyecdysone (20E) in molting-arrested infected males, whereas 20E was not detected after normal molting in uninfected males. However, expression of the ecdysone-inactivating enzyme ecdysone oxidase was not reduced during the molting stage in infected males.

OGV infection induces male-specific transcriptional reprogramming and endocrine disruption in H. magnanima. These results suggest that delayed or incomplete 20E clearance is associated with molting arrest, while unchanged ecdysone oxidase expression indicates that additional regulatory mechanisms are involved. These findings provide new molecular insight into virus-induced male-killing.