Serotonin Receptor B May Lock the Gate of PTTH Release/Synthesis in the Chinese Silk Moth, Antheraea pernyi; A Diapause Initiation/Maintenance Mechanism?

Abstract

The release of prothoracicotropic hormone, PTTH, or its blockade is the major endocrine switch regulating the developmental channel either to metamorphosis or to pupal diapause in the Chinese silk moth, Antheraea pernyi. We have cloned cDNAs encoding two types of serotonin receptors (5HTRA and B). 5HTRA-, and 5HTRB-like immunohistochemical reactivities (-ir) were colocalized with PTTH-ir in two pairs of neurosecretory cells at the dorsolateral region of the protocerebrum (DL). Therefore, the causal involvement of these receptors was suspected in PTTH release/synthesis. The level of mRNA5HTRB responded to 10 cycles of long-day activation, falling to 40% of the original level before activation, while that of 5HTRA was not affected by long-day activation. Under LD 16:8 and 12:12, the injection of dsRNA5HTRB resulted in early diapause termination, whereas that of dsRNA5HTRA did not affect the rate of diapause termination. The injection of dsRNA5HTRB induced PTTH accumulation, indicating that 5HTRB binding suppresses PTTH synthesis also. This conclusion was supported pharmacologically; the injection of luzindole, a melatonin receptor antagonist, plus 5th inhibited photoperiodic activation under LD 16:8, while that of 5,7-DHT, induced emergence in a dose dependent fashion under LD 12:12. The results suggest that 5HTRB may lock the PTTH release/synthesis, maintaining diapause. This could also work as diapause induction mechanism.

Apoptosis and necrosis during the circadian cycle in the centipede midgut

“…c Bar=1.2 μm. d Bar=0.9 μm behavior, physiology, and metabolism are located in the nervous system, peripheral clocks have also been described in the digestive and/or reproductive system (Tomioka et al 2012;Wang et al 2013;Park et al 2013).…”

Identification of the prothoracicotropic hormone (Ptth) coding gene and localization of its site of expression in the pea aphid Acyrthosiphon pisum

“…PTTH thus plays a key role in the control of moulting and metamorphosis and, consequently, in the transition from juvenile to adult stages. Moreover, both PTTH release or blockade have been reported to act as a switch to terminate or initiate larval and pupal diapauses (Zhang & Denlinger, ; Bloch et al ., ; Mizoguchi et al ., ; Wang et al ., ; De Loof et al ., ). Diapause is very often a response triggered by day length (photoperiod) variation (Saunders, ; Nelson et al ., ; Koštál, ; Hand et al ., ).…”

“…Diapause is very often a response triggered by day length (photoperiod) variation (Saunders, 2002;Nelson et al, 2009;Ko st al, 2011;Hand et al, 2016). Although the cues that stimulate NSCs to secrete PTTH are known in some insect species (Richter et al, 2000;Mohamed et al, 2014;Wang et al, 2013Wang et al, , 2015, it is not known what factors at the molecular level control the decision to activate or to stop PTTH synthesis and/or release (Vafopoulou & Steel, 1996;Steel & Vafopoulou, 2006;Vafopoulou et al, 2007). Similar to what is known in vertebrates (Dardente et al, 2010), a role for the circadian clock in insect photoperiodic responses has been proposed by several groups (Ikeno et al, 2010;Pegoraro et al, 2014;Denlinger & Armbruster, 2016;Omura et al, 2016;Reppert et al, 2016).…”

Genomic basis of circannual rhythm in the european corn borer moth

“…As population genomic analysis will 76 identify mutations within individual genes underlying changes in measured traits, as well as loci controlling 77 unmeasured traits subject to correlated selection in nature (such as temperature tolerance), we view the 78 approaches as parts of a complementary, two-pronged forward-genetics strategy to characterize the genetics 79 of natural variation in circannual rhythm. 80…”