Phototransduction and circadian entrainment are the key pathways in the signaling mechanism for the baculovirus induced tree-top disease in the lepidopteran larvae

Abstract

The tree-top disease is an altered behavioral state, displayed by baculovirus-infected lepidopteran larvae, and characterized by climbing to an elevated position before death. The detailed molecular mechanism underlying this phenomenal behavior change has not been reported yet. Our study focused on the transcriptomic changes in the host larvae due to baculovirus infection from pre-symptomatic to tree-top disease stage. Enrichment map visualization of the gene sets grouped based on the functional annotation similarity revealed 34 enriched pathways in signaling mechanism cluster during LdMNPV induced tree-top disease in third instar Lymantria dispar asiatica larvae. Directed light bioassay demonstrated the positively phototactic larvae during tree-top disease and the gene expression analysis showed altered rhythmicity of the host’s core circadian genes (per and tim) during the course of infection emphasizing the role of Circadian entrainment and Phototransduction pathways in the process, which also showed maximum interactions (>50% shared genes with 24 and 23 pathways respectively) among other signaling pathways in the enrichment map. Our study provided valuable insights into different pathways and genes, their coordinated response and molecular regulation during baculovirus infection and also improved our understanding regarding signaling mechanisms in LdMNPV induced tree-top disease.

Identification of Core Genes of Toll-like Receptor Pathway from Lymantria dispar and Induced Expression upon Immune Stimulant

“…TLR pathway core genes (TLRs, MyD88, IRAK1, IRAK4, JNK and AP-1) were identified from a previously constructed L. dispar transcriptome [15]. Open reading frames (ORFs) and deduced amino acid (aa) sequences were determined using NCBI ORF finder (https: //www.ncbi.nlm.nih.gov/orffinder/, accessed on 6 March 2021).…”

Diel and Circadian Patterns of Locomotor Activity in the Adults of Diamondback Moth (Plutella xylostella)

“…Female moths produce and release pheromones at specific times of the day, which is synchronized with the rhythm of male moths; those are sensitive to pheromones [8]. The phototransduction and circadian rhythm synchronization play a key role in the signal transduction mechanism of lepidopteran treetop disease caused by baculovirus [9].…”

The PI3K/AKT Pathway and PTEN Gene Are Involved in “Tree-Top Disease” of Lymantria dispar

“…Baculoviruses have been shown to induce a series of behavioral changes in infected larvae including prolonged instars and the behavior of climbing to an elevated location before death [ 4 , 5 , 6 ]. In the last decade, some of the primary genes responsible for NPV manipulation have been identified, providing insight into NPV-led influences on the host even when depending on just one gene [ 6 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 19 , 21 , 40 , 41 ]. However, the details of the interactions between the host and baculovirus have rarely been explored.…”

“…Comparing the differentially expressed genes (DEGs) of brains that were infected with BmNPV and healthy silkworms, it was shown that BmNPV-induced hyperactive behavior was correlated with synaptic transmissions, serotonin receptor signaling and circadian rhythm pathways [ 16 ]. It was reported that in LdMNPV-infected hyperactive larvae, the photosensitivity was increased and the rhythmicity-relevant genes, especially period ( per ) and timeless ( tim ), were impacted [ 17 ]. The process of the baculovirus manipulating the infected host to produce progeny is seemingly simple.…”