“…Our observations showed that light from above is essential for tree-top disease and this is in accordance with previous findings [20,38]. Our efforts to further dissect the effect and preference of different wavelengths of light during the process unveiled the higher preference of infected larvae toward the blue light coming from above.…”
Section: Discussionsupporting
confidence: 92%
“…Similarly, adult lepidopteran insects were also found to be attracted toward blue or shorter wavelengths of light, and that might assist them with orientation cues especially for finding suitable oviposition sites which is not the case for their larvae [44,52]. Therefore, the infected larva’s high preference for the blue light might have indicated their search for a place before death, rather than the search for leaves in the canopy for food because the infected ones consume less food and have reduced growth rate and development [38].…”
Lepidopteran larvae upon infection by baculovirus show positive photo-tactic movement during tree-top disease. In light of many insects exploiting specific spectral information for the different behavioral decision, each spectral wavelength of light is an individual parsimonious candidate for such behavior stimulation. Here, we investigated the responses of third instar Helicoverpa armigera larvae infected by Helicoverpa armigera nucleopolyhedrovirus (HearNPV) to white (broad-spectrum), blue (450–490 nm), UVA (320–400 nm), and UVB (290–320 nm) lights for the tree-top disease. Our findings suggest that tree-top phenomenon is induced only when the light is applied from above. Blue, white and UVA lights from above induced tree-top disease, causing infected larvae to die in an elevated position compared to those larvae living in the complete dark. In contrast, UVB from above did not induce tree-top disease. Blue light exerted the maximum photo-tactic response, significantly (p < 0.01) higher than white light. The magnitude of the response decreased with decreasing wavelength to UVA, and no response at UVB. Our results suggested that the spectral wavelength of the light has a significant effect on the induction of the tree-top disease in H. armigera third instar larvae infected with HearNPV.
“…Our observations showed that light from above is essential for tree-top disease and this is in accordance with previous findings [20,38]. Our efforts to further dissect the effect and preference of different wavelengths of light during the process unveiled the higher preference of infected larvae toward the blue light coming from above.…”
Section: Discussionsupporting
confidence: 92%
“…Similarly, adult lepidopteran insects were also found to be attracted toward blue or shorter wavelengths of light, and that might assist them with orientation cues especially for finding suitable oviposition sites which is not the case for their larvae [44,52]. Therefore, the infected larva’s high preference for the blue light might have indicated their search for a place before death, rather than the search for leaves in the canopy for food because the infected ones consume less food and have reduced growth rate and development [38].…”
Lepidopteran larvae upon infection by baculovirus show positive photo-tactic movement during tree-top disease. In light of many insects exploiting specific spectral information for the different behavioral decision, each spectral wavelength of light is an individual parsimonious candidate for such behavior stimulation. Here, we investigated the responses of third instar Helicoverpa armigera larvae infected by Helicoverpa armigera nucleopolyhedrovirus (HearNPV) to white (broad-spectrum), blue (450–490 nm), UVA (320–400 nm), and UVB (290–320 nm) lights for the tree-top disease. Our findings suggest that tree-top phenomenon is induced only when the light is applied from above. Blue, white and UVA lights from above induced tree-top disease, causing infected larvae to die in an elevated position compared to those larvae living in the complete dark. In contrast, UVB from above did not induce tree-top disease. Blue light exerted the maximum photo-tactic response, significantly (p < 0.01) higher than white light. The magnitude of the response decreased with decreasing wavelength to UVA, and no response at UVB. Our results suggested that the spectral wavelength of the light has a significant effect on the induction of the tree-top disease in H. armigera third instar larvae infected with HearNPV.
“…1b,c ). A similar observation had been reported for the induction of tree-top disease in Spodoptera exigua third instar larvae infected by SeMNPV 18 , 20 . Figure 1 Larval climbing behavior during the course of time, ( a ) relationship between vertical position of the L .…”
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.
“…De-a lungul timpului, virusul respectiv a fost cunoscut sub denumirea de Borrelinavirus efficiens Holmes (Krieg 1961, Glowacka 1989, dar denumirea actuală este Lymantria monacha nucleopolyhedrovirus (NPV) și face parte din familia Baculoviridae, genul Alphabaculovirus (Thézé et al 2018). Între timp, s-a constatat că baculovirusurile afectează comportamentul larvelor și în cazul altor specii de lepidoptere (Goulson 1997, Harrison & Hoover 2012, van Houte et al, 2015, inducându-le un răspuns fototactic pozitiv care le face să urce în locuri expuse, cu lumină puternică.…”
In 2017, the media in England and other countries reacted frantically to the news that the caterpillars of Lasiocampa quercus in West Pennine Moors, in Lancashire, were struck by the "zombie virus". A similar phenomenon was observed in August 2018, in Calimani Mountains, Romania on about 30 ha area. The larvae of the alpina form of the subspecies L. quercus quercus were found in the crown of small Norway spuce (Picea abies) trees or on bushes of dwarf mountain pine (Pinus mugo) and-to a lesser extent-of juniper (Juniperus sp.). Some of them were alive, but anemic, and the others were dead, hanging upside down. Most dead larvae were still whole, but with a soft body, while only the torn skin remained of some of them. The symptoms presented by the larvae suggest that they died from an infection with Lasiocapa quercus NPV. Before dying, the larvae consumed needles of Norway spruce and dwarf mountain pine, after the depletion of their usual food resources in that place, namely the leaves of Vaccinium spp. The rainy weather of the previous two months (June and July) could have contributed to the spread of the disease among the larvae. This is the first case of mass proliferation of the L. quercus species observed and reported in Romania and also the first case of an epizootic caused by the baculovirus specific to this species in our country.
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