Fall armyworm changes its gut after viral infection

The fall armyworm (Spodoptera frugiperda) exhibits a rapid and dynamic molecular response in the midgut after ingestion of SfMNPV. Study identified structural, metabolic, and cellular changes within the first 24 hours. Results indicate remodeling of the intestinal barrier, activation of stress pathways, and a transition from apoptosis to tissue regeneration.

The research used transcriptomic sequencing at three time points: 1, 12, and 24 hours after oral inoculation of the virus. The analysis revealed a defined temporal pattern in the host response. The peak of gene expression occurred at 12 hours. There was a predominance of activated genes throughout the period.

The midgut suffered structural damage early on. Genes linked to the peritrophic matrix showed reduced expression within 1 hour. Subsequently, components of the basal lamina showed a decrease within 12 hours. This process indicates a loss of intestinal barrier integrity. Simultaneously, cytoskeletal genes increased expression between 12 and 24 hours. This pattern suggests cellular reorganization associated with viral infection.

Genes linked to stress

The study recorded a progressive increase in genes linked to endoplasmic reticulum stress. There was activation of autophagy pathways and the ubiquitin system between 12 and 24 hours. These mechanisms indicate an intensification of protein processing and degradation. The response suggests cellular adjustment in the face of viral protein accumulation.

In the initial phase, the insect activated detoxification mechanisms. ABC transporters and UDP-glycosyltransferase enzymes showed increased expression within 1 hour. This pattern indicates an attempt to eliminate toxic compounds. After 12 hours, a functional change occurred. Antioxidant enzymes, such as glutathione S-transferase and superoxide dismutase, began to predominate. This shift indicates increased oxidative stress during infection.

programmed death

The cellular response also involved programmed cell death. Genes linked to apoptosis increased expression within the first hour. This mechanism may limit viral dissemination. In later stages, activation of regeneration pathways occurred. Genes associated with the Wnt, mTOR, and Hippo pathways increased expression between 12 and 24 hours. This process indicates an attempt to repair the intestinal epithelium.

The number of differentially expressed genes reinforces the dynamic nature of the response. 499 genes were identified in 1 hour, 804 in 12 hours, and 750 in 24 hours. Most genes showed phase-specific behavior. Only a small fraction maintained constant expression over time.

Low viral load

The data also indicate a low viral load in the early stages. The amount of viral load remained below 0,002% of the total. This result confirms an early stage of infection. Even so, the host showed an intense molecular response.

The analysis points to a complex interaction between the virus and the host. SfMNPV induces structural and metabolic changes in the gut. The insect responds with defense and repair mechanisms. This balance defines the success of the infection.

Further information at doi.org/10.3390/insects17040401