–by J.P. Michaud, Professor in Entomology–Agriculture Research Center, Hays, KS
Collaborative research in China was featured in this summer’s edition of American Entomologist, and is relevant to control of headworms in Kansas sorghum.
https://academic.oup.com/ae/article-abstract/68/2/4/6605209?redirectedFrom=fulltext
This work was done on ‘Old World bollworm’, H. armigera, but its biology is very similar to that of corn earworm, H. zea.
The mechanisms by which the virus manipulates host behavior described therein are likely the same as those used by the HzeNPV that is the organism in the Heligen product we are using to control corn earworm in sorghum.
Instead of trying to pupate in the soil, infected larvae climb to the tops of plants where they die, assisting in the dispersal of the virus.
Here is the full abstract:
Abstract
Baculoviruses can induce climbing behavior in their caterpillar hosts to ensure they die at elevated positions to enhance virus transmission, providing an excellent model to study parasitic manipulation of host behavior. Here, we demonstrate that climbing behavior occurs mostly during daylight hours, and that the height at death of Helicoverpa armigera single nucleopolyhedrovirus (HearNPV)-infected larvae increases with the height of the light source. Phototaxic and electroretinogram (ERG) responses were enhanced after HearNPV-infection in host larvae, and ablation of stemmata in infected larvae prevented both phototaxis and climbing behavior. Through transcriptome and quantitative PCR, we confirmed that two opsin genes (a blue light-sensitive gene, HaBL, and a long wave-sensitive gene, HaLW) as well as the TRPL (transient receptor potential-like channel protein) gene, all integral to the host’s visual perception pathway, were significantly up-regulated after HearNPV infection. Knockout of HaBL, HaLW, or TRPL genes using the CRISPR/Cas9 system resulted in significantly reduced ERG responses, phototaxis, and climbing behavior in HearNPV-infected larvae. These results reveal that HearNPV alters the expression of specific genes to hijack host visual perception at fundamental levels – photoreception and phototransduction – in order to induce climbing behavior in host larvae.