Baculoviruses manipulate host climbing behaviour to ensure that the hosts die at elevated positions on host plants to facilitate virus proliferation and transmission, which is a process referred to as tree‐top disease. However, the detailed molecular mechanism underlying tree‐top disease has not been elucidated. Using RNA sequencing analysis, researchers recently showed that two hormone signals, juvenile hormone (JH) and 20‐hydroxyecdysone (20E), are key components involved in HaSNPV‐induced tree‐top disease in Helicoverpa armigera larvae.

RNAi‐mediated knockdown and exogenous hormone treatment assays demonstrated that 20E inhibits virus‐induced tree‐top disease, while JH mediates tree‐top disease behaviour. Knockdown of BrZ2, a downstream signal of JH and 20E, promoted HaSNPV‐induced tree‐top disease. They also found that two miRNAs target BrZ2 and are involved in the cross‐talk regulation between 20E and JH manipulating HaSNPV replication, time to death and HaSNPV‐induced tree‐top disease.



BrZ2 is targeted by miR‐8 and miR‐429 in Helicoverpa armigera larvae. (a) Predicted target sites of miR‐8 and miR‐429 in the 3′UTR of the H. armigera BrZ2 gene. (b) Relative luciferase activity following cotransfection of miR‐8 or miR‐429 agomir with a luciferase reporter gene linked to the 3′UTR of BrZ2 gene. (c) Relative expression of BrZ2, miR‐8 and miR‐429 in H. armigera larvae at 72 hr postinfection with one of two concentrations of HaSNPV or mock inoculated with PBS. (d, e) Relative expression of BrZ2 after injection of the agomir or antagomir, respectively, of miR‐8 and miR‐429 in H. armigera larvae. Bars represent the mean ± SE of three biological replicates. Bars with different letters are significantly different, p < .05. *.01 < p < .05; **p < .01

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S. Zhang  S. An, K. Hoover, Z. Li, X. Li, X. Liu, Z. Shen, H. Fang, V. I. D. Ros, Q. Zhang, X. Liu (2018) Host miRNAs are involved in hormonal regulation of HaSNPVtriggered climbing behaviour in Helicoverpa armigera Molecular Ecology doi: 10.1111/mec.14457 [abstract]

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