Symbiotic bracovirus of a parasite modulate host ecdysis process

Area of Science:

• Insect biology
• Molecular parasitology
• Endocrinology

Background:

• Parasitoids manipulate host development for their own survival.
• The precise molecular mechanisms of this host manipulation are not fully understood.
• Insect ecdysis, or molting, is a critical developmental process regulated by hormones.

Purpose of the Study:

• To investigate how the endoparasitoid Cotesia vestalis disrupts the larval-larval ecdysis of its host, Plutella xylostella.
• To identify the molecular players involved in this host-parasitoid interaction.
• To elucidate the signaling pathways targeted by the parasitoid.

Main Methods:

• Quantification of 20-hydroxyecdysone (20E) levels in host larvae.
• Measurement of ecdysone synthesis gene expression.
• Analysis of a specific Cotesia vestalis bracovirus (CvBV) gene, CvBV_28-5.
• Gene knockdown experiments for CvBV_28-5.
• Investigation of protein-protein interactions using Raf, a MAPK pathway component.

Main Results:

• Parasitization by C. vestalis led to the disappearance of the 20E peak and downregulation of ecdysone synthesis genes.
• The CvBV gene CvBV_28-5 was highly expressed before the host's 20E peak, suppressing this developmental signal.
• Knockdown of CvBV_28-5 altered the expression of 20E response transcription factors and ecdysis-related genes.
• CvBV_28-5 directly bound to Raf, a key regulator in the MAPK pathway controlling ecdysone synthesis.

Conclusions:

• Parasitoids can precisely modulate host ecdysis by targeting the MAPK-20E signaling pathway.
• The CvBV gene CvBV_28-5 plays a critical role in suppressing host ecdysone synthesis during a specific developmental window.
• This study provides novel insights into the molecular mechanisms of parasitoid manipulation of host development.