Effects of temperature and melatonin on day–night expression patterns of arginine vasotocin and isotocin mRNA in the diencephalon of a temperate wrasse Halichoeres tenuispinis

Most wrasses are protogynous species that swim to feed, reproduce during the daytime, and bury themselves under the sandy bottom at night. In temperate and subtropical wrasses, low temperature influences emergence from the sandy bottom in the morning, and induces a hibernation-like state in winter. We cloned and characterized the prohormone complementary DNAs (cDNAs) of arginine vasotocin (AVT) and isotocin (IT) in a temperate wrasse (Halichoeres tenuispinis) and examined the effects of day/night and temperature on their expression in the diencephalon, because these neurohypophysial peptides are related to the sex behavior of wrasses. The full-length cDNAs of pro-AVT and pro-IT were 938 base pairs (154 amino acids) and 759 base pairs (156 amino acids) in length, respectively. Both pro-peptides contained a signal sequence followed by the respective hormones and neurophysin connected by a Gly-Lys-Arg bridge. Reverse-transcription polymerase chain reaction (RT-PCR) revealed that pro-AVT mRNA expression was specifically observed in the diencephalon, whereas pro-IT mRNA expression was seen in the whole brain. Quantitative RT-PCR revealed that the mRNA abundance of pro-AVT and pro-IT was higher at midday (zeitgeber time 6; ZT6) than at midnight (ZT18) under 12 h light and 12 h darkness (LD 12:12) conditions, but not under constant light. Intraperitoneal injection of melatonin decreased the mRNA abundance of pro-AVT, but not of pro-IT. When fish were reared under LD 12:12 conditions at 25, 20, and 15 degrees C, day high and night low mRNA expressions of pro-AVT and pro-IT were maintained. A field survey revealed seasonal variation in the number of swimming fish at observatory sites; many fish emerged from the sandy bottom in summer, but not in winter, suggesting a hibernation-like state under the sandy bottom under low temperature conditions. We conclude that the day-night fluctuation of pro-AVT and pro-IT mRNA abundance in the brain is not affected by temperature and repeated under the sandy bottom in winter

Environmental Control of Annual Reproductive Cycle and Spawning Rhythmicity of Spinefoots

Proceedins of 8th Kuroshio University League Network Formation Toward the Sustainable Society in Kuroshio Region Through Cross-Boader Educatio

Tide-related changes in mRNA abundance of aromatases and estrogen receptors in the ovary and brain of the threespot wrasse Halichoeres trimaculatus

Author Posting. © The Author(s), 2018. This is the author's version of the work. It is posted here under a nonexclusive, irrevocable, paid-up, worldwide license granted to WHOI. It is made available for personal use, not for redistribution. The definitive version was published in Ocean Science Journal 53 (2018): 239-249, doi:10.1007/s12601-018-0016-0.The threespot wrasse (Halichoeres trimaculatus; Family Labridae) is a common coral reef species of the Indo-Pacific Ocean. Given that this species spawns daily at high tide (HT), we hypothesized that endocrine changes in relation to gonadal development are synchronized with the tidal cycle. To test this, we examined the transcript abundance of two cytochrome P450 aromatases (cyp19a and cyp19b) and two estrogen receptors (er and er) in the ovary and brain of this species in response to tidal change. When fish were collected around four tidal points [low tide (LT), flood tide (FT), high tide (HT), and ebb tide (ET)], gonadosomatic index and oocyte diameter increased around HT and FT, respectively. Ovulatory follicles were observed in ovaries around HT. Real-time quantitative polymerase-chain reaction revealed that mRNA abundance of cyp19a and er, but not er, in the ovary increased around ET and HT, respectively. On the other hand, mRNA levels of cyp19b in the forebrain were significantly higher around FT. Increases of er and er mRNA abundance around FT were observed in all areas of the brain and the midbrain, respectively. The changes in mRNA abundance of key genes involved in reproduction at specific tidal cycles, along with the development of the vitellogenic oocytes in the ovary, support our hypothesis that synchronization of endocrine changes to the tidal periodicity plays a role in the gonadal development of this species. We hypothesize that conversion of testosterone to E2 in the brain may be associated with the spawning behavior given that the wrasse exhibits group spawning with a territory-holding male around HT.This study was supported partially by the 21st Century COE program “The Comprehensive Analyses on Biodiversity in Coral Reef and Island Ecosystems in Asian and Pacific Regions” from the Ministry of Education, Culture, Sports, Science and Technology, Japan, JSPS KAKENHI Grant number 16H05796, and the Natural Sciences and Engineering Research Council (NSERC, Canada) Discovery Grant program

Lunar Phase-Dependent Expression of Cryptochrome and a Photoperiodic Mechanism for Lunar Phase-Recognition in a Reef Fish, Goldlined Spinefoot

Lunar cycle-associated physiology has been found in a wide variety of organisms. Recent study has revealed that mRNA levels of Cryptochrome (Cry), one of the circadian clock genes, were significantly higher on a full moon night than on a new moon night in coral, implying the involvement of a photoreception system in the lunar-synchronized spawning. To better establish the generalities surrounding such a mechanism and explore the underlying molecular mechanism, we focused on the relationship between lunar phase, Cry gene expression, and the spawning behavior in a lunar-synchronized spawner, the goldlined spinefoot (Siganus guttatus), and we identified two kinds of Cry genes in this animal. Their mRNA levels showed lunar cycle-dependent expression in the medial part of the brain (mesencephalon and diencephalon) peaking at the first quarter moon. Since this lunar phase coincided with the reproductive phase of the goldlined spinefoot, Cry gene expression was considered a state variable in the lunar phase recognition system. Based on the expression profiles of SgCrys together with the moonlight's pattern of timing and duration during its nightly lunar cycle, we have further speculated on a model of lunar phase recognition for reproductive control in the goldlined spinefoot, which integrates both moonlight and circadian signals in a manner similar to photoperiodic response

Circadian rhythm of melatonin secretion and growth-related gene expression in the tiger puffer Takifugu rubripes

Abstract Somatostatin (SS) and growth hormone-releasing hormone (GHRH) are primary factors regulating growth hormone (GH) secretion in the pituitary. To date, it remains unknown how this rhythm is controlled endogenously, although there must be coordination of circadian manners. Melatonin was the main regulator in biological rhythms, and its secretion has fluctuation by photic information. But relationship between melatonin and growth-related genes (ghrh and ss) is unclear. We investigated circadian rhythms of melatonin secretion, ghrh and ss expressions, and correlation between melatonin with growth-related genes in tiger puffer Takifugu rubripes. The melatonin secretion showed nocturnal rhythms under light and dark (LD) conditions. In constant light (LL) condition, melatonin secretion has similar patterns with LD conditions. ss1 mRNA was high during scotophase under LD conditions. But ss1 rhythms disappeared in LL conditions. Ghrh appeared opposite expression compared with melatonin levels or ss1 expression under LD and LL. In the results of the melatonin injection, ghrh and ss1 showed no significant expression compared with control groups. These results suggested that melatonin and growth-related genes have daily or circadian rhythms in the tiger puffer. Further, we need to know mechanisms of each ss and ghrh gene regulation

Anti-Obesity Effects of Polymethoxyflavone-Rich Fraction from Jinkyool (Citrus sunki Hort. ex Tanaka) Leaf on Obese Mice Induced by High-Fat Diet

Polymethoxyflavones (PMFs) are flavonoids exclusively found in certain citrus fruits and have been reported to be beneficial to human health. Most studies have been conducted with PMFs isolated from citrus peels, while there is no study on PMFs isolated from leaves. In this study, we prepared a PMF-rich fraction (PRF) from the leaves of Citrus sunki Hort ex. Tanaka (Jinkyool) and investigated whether the PRF could improve metabolic decline in obese mice induced by a high-fat diet (HFD) for 5 weeks. The HFD-induced obese mice were assigned into HFD, OR (HFD + orlistat at 15.6 mg/kg of body weight/day), and PRF (HFD + 50, 100, and 200 mg/kg of body weight/day) groups. Orlistat and PRF were orally administered for 5 weeks. At the end of the experiment, the serum biochemical parameters, histology, and gene expression profiles in the tissues of each group were analyzed. The body weight gain of the obese mice was significantly reduced after orlistat and PRF administration for 5 weeks. PRF effectively improved HFD-induced insulin resistance and dyslipidemia. Histological analysis in the liver demonstrated that PRF decreased adipocyte size and potentially improved the liver function, as it inhibited the incidence of fatty liver. PRF activated AMP-activated protein kinase (AMPK), acetyl-CoA carboxylase (ACC), and hormone-sensitive lipase (HSL) in HFD-induced obese mice. Moreover, liver transcriptome analysis revealed that PRF administration enriched genes mainly related to fatty-acid metabolism and immune responses. Overall, these results suggest that the PRF exerted an anti-obesity effect via the modulation of lipid metabolism