CasEcR and CasMIH Genes in the Blue Crab, Callinectes sapidus: A Temporal Evaluation and Melatonin Effects

The effect of thermal stress on the X-organ/sinus gland proteome of the estuarine blue crab Callinectes sapidus during the intermolt and premolt stages

Survival of brachyuran crabs is temperature-dependent and thermal stress promotes changes during molting. We aimed to decipher the impact of thermal stresses on the X-organ/sinus gland (XO/SG) complex, a temperature-sensitive neuroendocrine tissue involved in the molting regulation of Callinectes sapidus during the intermolt and premolt phases. We employed a proteogenomic approach using specimens subjected to control (24 °C), cold (19 °C), and heat (29 °C) temperatures. A total of 1463 protein groups with at least two unique peptides were identified and quantified. C. sapidus in the premolt stage exposed to the cold condition exhibited a proteome closely resembling that of the intermolt stage, as evidenced by measurements of circulating ecdysteroid levels. Compared to the intermolt at control temperature, the premolt stage exhibited increased energy metabolism, structural changes in the cuticle mediated by chitin metabolism and glycoproteins, biosynthesis of methyl farnesoate (MF), and elevated tissue levels of molt-inhibiting hormone (MIH) and crustacean hyperglycemic hormone (CHH), indicating lower secretion rates. Heat temperature (29 °C) seems to induce mitochondrial metabolism in the intermolt XO/SG, while cold temperature elicited a delayed molt cycle in the premolt phase, marked by reduced tissue levels of CHH, indicating increased secretion and Y-organ (YO) inhibition, and decreased MF production (reduced YO stimulation). SIGNIFICANCE STATEMENT: Temperature plays a pivotal role in regulating the metabolism, growth, molting, reproduction, and survival of crabs, such as the blue crab (Callinectes sapidus). Despite the blue crab's significance on both economic and ecological realms, there has been a notable lack of molecular information related to this species and therefore a gap in our knowledge of the blue crab's molecular makeup and genetic diversity. This research established a comprehensive proteome landscape to elucidate the molecular and functional changes in the XO/SG complex involved in the molting process of C. sapidus, and how thermal stresses significantly influence biotransformation processes. Utilizing a proteogenomics approach with multi-round homologous database analysis, we have generated a highly accurate protein repertoire with at least two unique peptide of XO/SG tissue proteome. This resource will be invaluable for future molecular analyses of this species. Our findings demonstrate that thermal stresses induced specific modifications in the XO/SG tissue, depending on the molt cycle phase. Temperature-mediated responses influences the biological processes, enhancing the functional morphogenesis and comprehensive metabolic adaptations on molting cycle supported by a relationship between the XO/SG tissue proteome and circulating ecdysteroid levels.

Temperature-driven changes in the neuroendocrine axis of the blue crab Callinectes sapidus during the molt cycle

Environmental cues such as temperature induce macroscopic changes in the molting cycle of crustaceans, however, the physiological mechanisms behind these changes remain unclearWe aimed to investigate the regulatory mechanisms in the intermolt and premolt stages of the Callinectes sapidus molt cycle in response to thermal stimuli. The concentration of ecdysteroids and lipids in the hemolymph, and the expression of heat shock proteins (HSPs) and molt key genes were assessed at 19 °C, 24 °C and 29 °C. The premolt animals exhibited a much larger response to the colder temperature than intermolt animals. Ecdysteroids decreased drastically in premolt animals, whereas the expression of their hepatopancreas receptor (CasEcR) increased, possibly compensating for the low hemolymphatic levels at 19 °C. This decrease might be due to increased HSPs and inhibited ecdysteroidogenesis in the Y-organ. In addition, the molting-inhibiting hormone expression in the X-organ/sinus gland (XO/SG) remained constant between temperatures and stages, suggesting it is constitutive in this species. Lipid concentration in the hemolymph, and the expression of CasEcR and CasHSP90 in the XO/SG were influenced by the molting stage, not temperature. On the other hand, the expression of HSPs in the hepatopancreas is the result of the interaction between the two factors evaluated in the study. Our results demonstrated that temperature is an effective modulator of responses related to the molting cycle at the endocrine level and that temperature below the control condition caused a greater effect on the evaluated responses compared to the thermostable condition, especially when the animal was in the premolt stage.

Effects of molting on the expression of ecdysteroid responsive genes in the crustacean molting gland (Y-organ)

Ecdysteroid molting hormones coordinate arthropod growth and development. Binding of 20-hydroxyecdysone (20E) to ecdysteroid receptor EcR/RXR activates a cascade of nuclear receptor transcription factors that mediate tissue responses to hormone. Insect ecdysteroid responsive and Forkhead box class O (FOXO) transcription factor gene sequences were used to extract orthologs from blackback land crab (Gecarcinus lateralis) Y-organ (YO) transcriptome: Gl-Ecdysone Receptor (EcR), Gl-Broad Complex (Br-C), Gl-E74, Gl-Hormone Receptor 3 (HR3), Gl-Hormone Receptor 4 (HR4), Gl-FOXO, and Gl-Fushi tarazu factor-1 (Ftz-f1). Quantitative polymerase chain reaction quantified mRNA levels in tissues from intermolt animals and in YO of animals induced to molt by multiple limb autotomy (MLA) or eyestalk ablation (ESA). Gl-EcR, Gl-Retinoid X Receptor (RXR), Gl-Br-C, Gl-HR3, Gl-HR4, Gl-E74, Gl-E75, Gl-Ftz-f1, and Gl-FOXO were expressed in all 10 tissues, with Gl-Br-C, Gl-E74, Gl-E75, and Gl-HR4 mRNA levels in the YO lower than those in most of the other tissues. In MLA animals, molting had no effect on Gl-Br-C, Gl-E74, and Gl-Ftz-f1 mRNA levels and little effect on Gl-EcR, Gl-E75, and Gl-HR4 mRNA levels. Gl-HR3 and Gl-FOXO mRNA levels were increased during premolt stages, while Gl-RXR mRNA level was highest during intermolt and premolt stages and lowest at postmolt stage. In ESA animals, YO mRNA levels were not correlated with hemolymph ecdysteroid titers. ESA had no effect on Gl-EcR, Gl-E74, Gl-HR3, Gl-HR4, Gl-Ftz-f1, and Gl-FOXO mRNA levels, while Gl-RXR, Gl-Br-C, and Gl-E75 mRNA levels were decreased at 3 days post-ESA. These data suggest that transcriptional up-regulation of Gl-FOXO and Gl-HR3 contributes to increased YO ecdysteroidogenesis during premolt. By contrast, transcriptional regulation of ecdysteroid responsive genes and ecdysteroidogenesis were uncoupled in the YO of ESA animals.

Melatonin injection and red light irradiation affect the antioxidant response and cell damage in disk abalone (Haliotis discus hannai) exposed to high water temperatures

The effects of red light-emitting diode (LED) light irradiation (630 nm, 0.5 W/m2) and melatonin (10-8 and 10-7 M) on oxidative stress and physiological responses in abalones exposed to high temperatures (28°C) were investigated. Changes in messenger RNA (mRNA) expressions of melatonin receptor (MT-R), heat shock protein 70 (HSP70), and antioxidant enzymes, as well as alterations in H2O2 levels in the hemolymph, were examined. The results revealed that high-temperature-stressed abalones treated with melatonin injections or exposed to red LED light showed a significant increase in MT-R mRNA expression, while HSP70 mRNA expression decreased. Notably, HSP70 mRNA expression levels in the red LED light-irradiated group were similar to those in the group injected with 10-8 M melatonin after 24 h exposure. Abalones treated with melatonin at 20°C or irradiated with red LED light exhibited decreased H2O2 levels and reduced antioxidant enzyme mRNA expression compared with those of the control group. However, the high-temperature environment induced oxidative stress in abalones, leading to increased antioxidant enzyme mRNA expression compared with that under 20°C conditions. Moreover, abalones exposed to high-temperature stress exhibited hepatopancreatic DNA damage, which was attenuated by melatonin treatment or red LED light irradiation. Hence, red LED light reduces oxidative stress, boosts antioxidant enzymes, and alleviates DNA damage in high-temperature-stressed abalones, akin to 10-8 M melatonin treatment. Therefore, considering the practical challenges of continuous melatonin administration to abalones, utilizing red LED light emerges as a practical, effective alternative to protect abalones from oxidative stress compared to 10-8 M melatonin treatment.