Induction of diapause by clock proteins period and timeless via changes in PTTH and ecdysteroid titer in the sugar beet moth, Scrobipalpa ocellatella (Lepidoptera: Gelechiidae)

Abstract

The sugar beet moth, Scrobipalpa ocellatella (Boyd), one of the most severe sugar beet pests, causes quantitative and qualitative yield losses late in the autumn. Previously, it was shown that low temperature and short-day photoperiod together cause diapause induction in pupae. Here, the interaction of the critical elements of the diapause induction, including the period (PER), timeless (TIM), prothoracicotropic hormone (PTTH), and ecdysteroid titer, were investigated. Immunohistochemistry results showed that the number of period immunoreactivity (PER-ir) and TIM-ir cells in nondiapause pupae (NDP) was lower than in the brain of the diapause pupae (DP). Moreover, the number of PER-ir and TIM-ir cells in the protocerebrum and optic lobe (OL) of NDP was lower than DP. Moreover, lower PTTH content in the brain and hemolymph of DP was confirmed by competitive enzyme-linked immunosorbent assay. Enzyme immunoassay showed a lower 20-hydroxyecdysone (20E) titer in the hemolymph of the DP compared with the NDP. Within a short-day condition, PER and TIM titers increased in the brain leading to decreasing PTTH titers in the brain and hemolymph that caused decreasing 20E titer in the hemolymph, leading to the induction of diapause. This study suggests that PER and TIM could be one of the brain factors that play an essential role in regulating diapause in S. ocellatella.

Mutation of the clock gene timeless disturbs diapause induction and adult emergence rhythm in Helicoverpa armigera

“…23,25 In the sugar beet moth, Scrobipalpa ocellatella, TIM and PER immunoreactivity cells in the brain of nondiapause pupae are less abundant than in that of diapause pupae. 29 This study suggests that Tim is likely an important molecule for inducing diapause in lepidopteran pests, but there is no reverse genetic evidences proving this.…”

Sublethal effects of fenoxycarb on female reproduction in Helicoverpa armigera (Lepidoptera: Noctuidae)

“…To determine the concentration of ecdysteroid in ovaries, the enzyme immune assay method (Cayman Chemicals, Inc., Ann Arbor, Michigan, United States of America) was used (Ahmadi et al 2021; Hackney et al 2012).…”

Effects of neuropeptide F2 on female reproduction in the cotton bollworm, Helicoverpa armigera (Lepidoptera: Noctuidae)

“…The enzyme immunoassay (EIA) method was used to determine the concentration of ecdysteroid in ovaries and haemolymph (Ahmadi et al, 2021). To this end, newly emerged adult females were injected with NPF2 dsRNA on days 1 and 3.…”

“…The product of this enzymatic reaction has a distinct yellow colour, is determined spectrophotometrically and is proportional to the amount of 20E tracer bound to the well, which is inversely proportional to the amount of free 20E present in the well during incubation. So, eventually, the absorbance with a microplate reader spectrometer (BioTek, USA) was read at 412 nm (Ahmadi et al, 2021; Hackney et al, 2012).…”

“…Then, on the seventh day, haemolymph and ovary samples were isolated to determine the concentration of ecdysteroid levels using EIA (Cayman Chemicals, Inc., USA). The assay is based on competition between 20-hydroxyecdysone and a 20-hydroxyecdysone-acetylcholinesterase ally, the absorbance with a microplate reader spectrometer (BioTek, USA) was read at 412 nm (Ahmadi et al, 2021;Hackney et al, 2012).…”