Location: Pest Management and Biocontrol ResearchTitle: RNAi-mediated knockdown of the Halloween gene spookiest (CYP307B1) impedes adult eclosion in the western tarnished plant bug, Lygus hesperus
|Van Ekert, Evelien|
|WANG, MEIXIAN - Zhejiang University|
|MIAO, YUN-GEN - Zhejiang University|
Submitted to: Insect Molecular Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/26/2016
Publication Date: 5/18/2016
Publication URL: http://handle.nal.usda.gov/10113/63135
Citation: Van Ekert, E., Wang, M., Miao, Y., Brent, C.S., Hull, J.J. 2016. RNAi-mediated knockdown of the Halloween gene spookiest (CYP307B1) impedes adult eclosion in the western tarnished plant bug, Lygus hesperus. Insect Molecular Biology. 25(5):550-565.
Interpretive Summary: A group of chemical messengers, the ecdysteroid hormones, play a critical role in coordinating insect growth, development, and reproduction. The actions of these hormones depends on the amounts produced, and the timing of production. A suite of chemical reactions, which are partly understood in some model insects, controls the amounts and timing of ecdysteroid production. These processes are completely unknown in many important pest insects, including the western tarnished plant bug (Lygus). ARS scientists at Maricopa, AZ showed a gene (called 'spookiest') was a key regulator of ecdysteroid hormone in Lygus. When the activity of 'spookiest' was blocked, immature Lygus did not complete development to adults, or they died during the transition to adulthood. Also, blocking 'spookiest' prevented normal egg development in adult female Lygus. When 'spookiest' was disrupted but artificial hormone was applied, normal development resumed. This is the first demonstration of the occurrence and activity of the 'spookiest' gene in Lygus. The results pave the way for development of novel, genetic-based control tactics for this important crop pest.
Technical Abstract: Ecdysteroids play a critical role in coordinating insect growth, development, and reproduction. A suite of cytochrome P450 monooxygenases coded by what are collectively termed Halloween genes mediate ecdysteroid biosynthesis. In this study, we describe cloning and RNAi-mediated knockdown of the CYP307B1 Halloween gene (spookiest) in the western tarnished plant bug, Lygus hesperus. Transcripts for L. hesperus spookiest (LhSpot) were amplified from all life stages and correlated well with timing of the ecdysteroid pulse. In adults, LhSpot was amplified from heads of both genders as well as female reproductive tissues. Heterologous expression of a LhSpot fluorescent chimera in cultured insect cells co-localized with a fluorescent marker of the endoplasmic reticulum/secretory pathway. RNAi-mediated knockdown of LhSpot in fifth instars reduced expression of ecdysone-responsive genes E74 and E75, and prevented adult development. This developmental defect was rescued following application of exogenous 20-hydroxyecdysone but not exogenous 7-dehydrocholesterol. The unequivocal RNAi effects on Lygus development and the phenotypic rescue by 20-hydroxyecdysone are causal proof of the involvement of LhSpot in ecdysteroid biosynthesis and related developmental processes, and may provide an avenue for development of new control measures against L. hesperus.