Cloning and distribution of a putative octopamine/tyramine receptor in the central nervous system of the freshwater prawn Macrobrachium rosenbergii

Transcriptome analysis of reproductive tract tissues of male river prawn Macrobrachium americanum

BACKGROUND

The river prawn, Macrobrachium americanum (M. americanum), is one of the largest prawns of the genus in Latin America and is an amphidromous species distributed along the Pacific coast of America. This prawn has commercial value due to its size and taste, making it a good option for aquaculture production. Its culture has been attempted in ponds and concrete tanks, but no successful technique can still support commercial production. Understanding the mechanisms that regulate reproduction at the molecular level is very important. This knowledge can provide tools for manipulating transcripts, which could increase the number or size of animals in the culture. Our understanding of the mechanism that regulates the reproduction of M. americanum at the molecular level is limited.

AIM

Perform and analyze the transcriptome assembly of the testes, vas deferens, and terminal ampulla of M. americanum. to provide new molecular information about its reproduction.

METHODS AND RESULTS

The cDNA library was constructed and sequenced for each tissue to identify novel transcripts. A combined transcriptome with the three tissues was assembled using Trinity software. Unigenes were annotated using BLASTx and BLAST2GO. The transcriptome assembly generated 1,059,447 unigenes, of which 7222 genes had significant hits (e-value < 1 × 10-5) when compared against the Swiss-Prot database. Around 75 genes were related to sex determination, testis development, spermatogenesis, spermiogenesis, fertilization, maturation of testicular cells, neuropeptides, hormones, hormone receptors, and/or embryogenesis.

CONCLUSIONS

These results provide new molecular information about M. americanum reproduction, representing a reference point for further genetic studies of this species.

Molecular characterization and functional roles for Vibrio alginolyticus resistance of an octopamine/tyramine receptor of the white shrimp, Litopenaeus vannamei

Octopamine and Tyramine are biogenic amines that have been demonstrated to play an important immunological role in white shrimp, Litopenaeus vannamei. G protein-coupled receptors, known as seven-transmembrane domain receptors, are a variety of neurotransmitter receptors which are sensitive to biogenic amines for initiating the cell signaling pathway. In present study, we cloned and characterized an octopamine/tyramine receptor (LvOA/TA-R) from the hemocytes of L. vannamei, with a 1194 b.p. open reading frame that encodes 398 amino acids. Several bioinformatics analyses indicated that LvOA/TA-R had seven conserved hydrophobic transmembrane domains. The phylogenetic analysis and multiple sequence alignment indicated that LvOA/TA-R was orthologous to the OA/TA receptor of tiger shrimp, P. monodon. LvOA/TA-R was expressed in hemocytes and nervous tissue including circumoesphageal connective tissue and the thoracic and abdominal ganglia. Significant increases in LvOA/TA-R occurred in hemocytes of L. vannamei under Vibrio alginolyticus infection within 30-60 min of infection. Here, we demonstrated that LvOA/TA-R expression is upregulated in response to Vibrio alginolyticus infection and appears to be functionally responsible for the observed immune response. These results suggest that LvOA/TA-R mediates regulation of immunity, which promotes the resistance of L. vannamei to V. alginolyticus.

The temporary modulation of tyramine on immune responses, carbohydrate metabolism, and catecholamines in Macrobrachium rosenbergii

Tyramine (TA), a biogenic monoamine, plays various important physiological roles including immunological regulation in invertebrates. In this study, the effects of TA on the regulation of immune resistance, carbohydrate metabolism and biogenic monoamine, as well as its signaling pathway in Macrobrachium rosenbergii were determined. Results showed that total haemocyte count, hyaline cells, semigranular cells, and phenoloxidase activity per 50 μL of haemolymph and per granulocyte (the sum of semigranular and granular cells) at 0.5 h as well as phagocytic activity and clearance efficiency to Lactococcus garvieae at 1 h of prawn injected with TA at 1 nmol prawn^-1 significantly increased, but the significantly decreased plasma lysozyme activity, phagocytic activity, clearance efficiency, and haemolymph glucose and dopamine were observed in prawn injected with TA at 10 nmol prawn^-1 for 0.5 h. Respiratory bursts and haemolymph lactate in two TA-injection treatments at 0.5 h and 0.5-1 h, respectively, were significantly higher than those of the saline control, and in addition, TA depressed dopamine release in a dose-dependent manner after 0.5 h of TA injection. All the examined parameters returned to control levels after prawn injected with TA for 2 h. The inhibited effect of TA (at 10 nmol prawn^-1 injection) on the phagocytic activity and clearance efficiency to pathogens was blocked by prazosin (an α1 adrenoceptors antagonist). For prawn received TA for 1 h then challenged with Lactococcus garvieae at 2 × 10⁵ colony-forming units prawn^-1, the survival ratio of TA 1 nmol prawn^-1-injected prawn significantly increased by 20%, compared to the saline-challenged control or TA 10 nmol prawn^-1-injected prawn after 144 h of challenge. These results suggested that the level of dopamine release suppression regulated by TA resulted in the immunoenhancing or immunosuppressive effects in prawn, and the signaling pathways of TA in mediating immune function were through octopamine (OA)/TA receptors.

Identification of putative amine receptor complement in the eyestalk of the crayfish, Procambarus clarkii

In decapod crustaceans, the amines dopamine, octopamine, serotonin, and histamine are known to serve as locally released and/or circulating neuromodulators. While many studies have focused on determining the modulatory actions of amines on decapod nervous systems, comparatively little is known about the identity of the receptors through which they exert their actions. Here, a crayfish, Procambarus clarkii, tissue-specific transcriptome was used to identify putative amine receptors in the eyestalk, a structure composed largely of the eyestalk ganglia, including the neuroendocrine X-organ-sinus gland system, and retina. Transcripts encoding 17 distinct putative amine receptors, three dopamine (one dopamine 1-like, one dopamine 2-like, and one dopamine/ecdysteroid-like), five octopamine (one alpha-like, three beta-like, and one octopamine/tyramine-like), three serotonin (two type-1-like and one type-7-like), and six histamine (five histamine-gated chloride channel A-like and one histamine-gated chloride channel B-like) were identified in the assembly. Comparison of the nucleotide sequence of the transcript encoding one predicted type-1-like serotonin receptor with that cloned previously from the P. clarkii nervous system shows the two sequences to be essentially identical, providing increased support for the validity of the transcripts used to deduce the proteins reported here. Reciprocal BLAST and structural/functional domain analyses support the protein family annotations ascribed to the putative P. clarkii receptors. These data represent the first large-scale description of amine receptors from P. clarkii, and as such provide a new resource for initiating gene-based studies of aminergic control of physiology/behavior at the level of receptors in this species.

The intracellular signaling pathway of octopamine upregulating immune resistance functions in Penaeus monodon

Octopamine (OA), a biogenic monoamine, is known to mediate several immune responses. This study analyzed the effects of OA on immunological regulation in the tiger shrimp Penaeus monodon. The immune parameters including total haemocyte count, differential haemocyte count, phenoloxidase activity, respiratory bursts, superoxide dismutase activity, and phagocytic activity and clearance efficiency in response to the pathogen, Photobacterium damselae, were determined when shrimp were individually injected with saline or OA at 100 or 1000 pmol shrimp^-1. In addition, the intracellular second messengers in haemocyte such as Ca²⁺ and adenosine 3',5'-cyclic monophosphate (cAMP) were examined in shrimp receiving saline or OA at 1 or 10 nmol shrimp^-1. Results showed that all of the immune parameters significantly increased at 2-4 h in OA-injected shrimp except hyaline cells in 100 pmol shrimp^-1-injected shrimp at 4 h, but phenoloxidase activity per granulocyte significantly decreased at 2-4 h. However, these had returned to saline control levels after receiving OA for 8 h except differential haemocyte count and phenoloxidase activity per granulocyte for 16 h. An injection of OA also significantly increased the survival rate of shrimp challenged with Pho. damselae. Shrimp receiving OA at 1 and 10 nmol shrimp^-1 significantly increased the intracellular Ca²⁺ concentration ([Ca²⁺]i) at 30-60 min and 30 min, and cAMP concentration [cAMP]i) at 5-15 min and 15 min, respectively. However, [Ca²⁺]i at 50-60 min, and [cAMP]i at 30-60 min returned to saline control when the shrimp received OA at 10 nmol shrimp^-1, and at 1 and 10 nmol shrimp^-1, respectively. These results suggest that OA administration by injection at ≤1000 pmol shrimp^-1 mediates transient upregulation of immunity together with the increased resistance of P. monodon to Pho. damselae, which are modulated through intracellular Ca²⁺ and cAMP second messenger pathways.

Tyramine's modulation of immune resistance functions in Litopenaeus vannamei and its signal pathway

Tyramine (TA), a neuroactive chemical, plays various important physiological roles in insects by activating distinct G-protein-coupled receptors (GPCRs). In this study, we investigated the effects of by pharmacological injection of TA on immune resistance regulation and its signal pathway in white shrimp Litopenaeus vannamei. Results showed significant increases in the total haemocyte count (THC), semigranular cells (SGCs), granular cells (GCs), phenoloxidase (PO) activity per 50 μL of haemolymph and respiratory bursts (RBs) at 0.5, 1, 2 and/or 4 h; hyaline cells (HCs) at 0.5 h, as well as phagocytic activity (PA) and clearance efficiency (CE) at 2, 4 and/or 8 h, but significantly decreased PO activity per granulocyte at 0.5-2 h for shrimp injected with TA at 100 and 1000 pmol shrimp^-1. Plasma lysozyme activities of TA-injected shrimp were significantly higher than those of the saline control at 1 h. All of the immune parameters had returned to control levels by 8 h after receiving TA except the clearance efficiency, which had returned to its control value by 16 h. The TA injection also significantly decreased the mortality of shrimp challenged with Vibrio alginolyticus. Furthermore, immune parameters of shrimp that received TA at 1000 pmol shrimp^-1 for 1 h were higher than those of shrimp that received the saline. The upregulating effect of TA was blocked by co-injection with phentolamine (Phe) in terms of the THC, HC, SGCs, PO activity, PA and CE; by co-injection with prazosin (Pra) in terms of the THC, HC, SGCs, PO activity, PA and CE; by co-injection with propranolol (Prop) in terms of the PA and CE; and by co-injection with metoprolol (Meto) in terms of the THC and SGCs. The most potent effect in immunocompetence of tested antagonists was Pra, and except for circulating haemocyte, it was Phe. These results suggest that ≤1000 pmol shrimp^-1 of a TA injection mediates transient upregulation of immunity, which in turn promotes the resistance of L. vannamei to V. alginolyticus, and the active effects are mediated via octopamine/tyramine (OA/TA) receptors.

Multiple Biogenic Amine Receptor Types Modulate Spider, Cupiennius salei, Mechanosensory Neurons

The biogenic amines octopamine (OA), tyramine (TA), dopamine (DA), serotonin (5-HT), and histamine (HA) affect diverse physiological and behavioral processes in invertebrates, but recent findings indicate that an additional adrenergic system exists in at least some invertebrates. Transcriptome analysis has made it possible to identify biogenic amine receptor genes in a wide variety of species whose genomes have not yet been sequenced. This approach provides new sequences for research into the evolutionary history of biogenic amine receptors and allows them to be studied in experimentally accessible animal models. The Central American Wandering spider, Cupiennius salei, is an experimental model for neurophysiological, developmental and behavioral research. We identified ten different biogenic amine receptors in C. salei transcriptomes. Phylogenetic analysis indicated that, in addition to the typical receptors for OA, TA, DA, and 5-HT in protostome invertebrates, spiders also have α1- and α2-adrenergic receptors, but lack TAR2 receptors and one invertebrate specific DA receptor type. In situ hybridization revealed four types of biogenic amine receptors expressed in C. salei mechanosensory neurons. We used intracellular electrophysiological experiments and pharmacological tools to determine how each receptor type contributes to modulation of these neurons. We show that arachnids have similar groups of biogenic amine receptors to other protostome invertebrates, but they lack two clades. We also clarify that arachnids and many other invertebrates have both α1- and α2-adrenergic, likely OA receptors. Our results indicate that in addition to an OAβ-receptor that regulates rapid and large changes in sensitivity via a G_s-protein activating a cAMP mediated pathway, the C. salei mechanosensory neurons have a constitutively active TAR1 and/or α2-adrenergic receptor type that adjusts the baseline sensitivity to a level appropriate for the behavioral state of the animal by a G_q-protein that mobilizes Ca²⁺.

Octopamine enhances the immune responses of freshwater giant prawn, Macrobrachium rosenbergii, via octopamine receptors

Octopamine (OA) is known to play an important role in regulating insect immune responses. In Macrobrachium rosenbergii (18.0 ± 1.7 g), OA at 25.0 and 250.0 pmol/prawn significantly increased THC, semigranular cells (SGCs) and PO activity in hemocytes per 50 μL hemolymph, hyaline cells, granular cells (GCs) and RBs in hemocytes per 10 μL hemolymph, and RBs per hemocyte, and however, significantly decreased PO activity per granulocyte (GC + SGC), which returned to control levels after 4 h of injection. The significantly increased phagocytic activity and clearance efficiency of prawn received OA for 8 h returned to control levels after 16 h of injection. In addition, the significantly increased glucose and decreased lactate were observed within 1 h of OA injection. In the susceptibility test, prawn received OA at 25.0 or 250.0 pmol/prawn for 2 h then challenged with Lactococcus garvieae at 10⁵ colony-forming units/prawn significantly increased the resistance of prawns by 23.3% and 30.0%, respectively, compared to the saline-challenged control after 144 h of challenge. In addition, the changes on immunocompetence induced by OA were observed to be blocked by adrenoceptors antagonists. These results suggest that OA administration at 250.0 pmol/prawn or less causes the mediate a transient up-regulation in immune and physiologic responses to promote the resistance of M. rosenbergii to L. garvieae, which are thought to be mediated by α- and β-adrenergic-like octopamine receptors.

Tyraminergic modulation of agonistic outcomes in crayfish

Octopamine, a biogenic amine, modulates various behaviors, ranging from locomotion and aggression to learning and memory in invertebrates. Several studies recently demonstrated that tyramine, the biological precursor of octopamine, also affects behaviors independent of octopamine. Here we investigated the involvement of tyramine in agonistic interaction of the male crayfish Procambarus clarkii. When male crayfish fight, larger animals (3-7% difference in body length) are more likely to win. By contrast, direct injection of tyramine or octopamine counteracted the physical advantage of larger animals. Tyramine or octopamine-injected naive large animals were mostly beaten by untreated smaller naive animals. This pharmacological effect was similar to the loser effect in which subordinate larger animals are frequently beaten by smaller animals. Furthermore, loser effects were partly eliminated by either injection of epinastine, an octopamine blocker, or yohimbine, a tyramine blocker, and significantly diminished by injection of a mixture of both blockers. We also observed that tyramine levels in the subesophageal ganglion were remarkably increased in subordinate crayfish after losing a fight. These results suggest that tyramine modulates aggressive levels of crayfish and contributes to the loser effect in parallel with octopamine.

Deep sequencing of transcriptomes from the nervous systems of two decapod crustaceans to characterize genes important for neural circuit function and modulation

BACKGROUND

Crustaceans have been studied extensively as model systems for nervous system function from single neuron properties to behavior. However, lack of molecular sequence information and tools have slowed the adoption of these physiological systems as molecular model systems. In this study, we sequenced and performed de novo assembly for the nervous system transcriptomes of two decapod crustaceans: the Jonah crab (Cancer borealis) and the American lobster (Homarus americanus).

RESULTS

Forty-two thousand, seven hundred sixty-six and sixty thousand, two hundred seventy-three contigs were assembled from C. borealis and H. americanus respectively, representing 9,489 and 11,061 unique coding sequences. From these transcripts, genes associated with neural function were identified and manually curated to produce a characterization of multiple gene families important for nervous system function. This included genes for 34 distinct ion channel types, 17 biogenic amine and 5 GABA receptors, 28 major transmitter receptor subtypes including glutamate and acetylcholine receptors, and 6 gap junction proteins - the Innexins.

CONCLUSION

With this resource, crustacean model systems are better poised for incorporation of modern genomic and molecular biology technologies to further enhance the interrogation of fundamentals of nervous system function.

In silico prediction of the G-protein coupled receptors expressed during the metamorphic molt of Sagmariasus verreauxi (Crustacea: Decapoda) by mining transcriptomic data: RNA-seq to repertoire

Against a backdrop of food insecurity, the farming of decapod crustaceans is a rapidly expanding and globally significant source of food protein. Sagmariasus verreauxi spiny lobster, the subject of this study, are decapods of underdeveloped aquaculture potential. Crustacean neuropeptide G-protein coupled receptors (GPCRs) mediate endocrine pathways that are integral to animal fecundity, growth and survival. The potential use of novel biotechnologies to enhance GPCR-mediated physiology may assist in improving the health and productivity of farmed decapod populations. This study catalogues the GPCRs expressed in the early developmental stages, as well as adult tissues, with a view to illuminating key neuropeptide receptors. De novo assembled contiguous sequences generated from transcriptomic reads of metamorphic and post metamorphic S. verreauxi were filtered for seven transmembrane domains, and used as a reference for iterative re-mapping. Subsequent putative GPCR open reading frames (ORFs) were BLAST annotated, categorised, and compared to published orthologues based on phylogenetic analysis. A total of 85 GPCRs were digitally predicted, that represented each of the four arthropod subfamilies. They generally displayed low-level and non-differential metamorphic expression with few exceptions that we examined using RT-PCR and qPCR. Two putative CHH-like neuropeptide receptors were annotated. Three dimensional structural modelling suggests that these receptors exhibit a conserved extracellular ligand binding pocket, providing support to the notion that these receptors co-evolved with their ligands across Decapoda. This perhaps narrows the search for means to increase productivity of farmed decapod populations.

Alterations in the levels and distribution of octopamine in the central nervous system and ovary of the Pacific white shrimp, Litopenaeus vannamei, and its possible role in ovarian development

Octopamine (OA) is a major neurotransmitter that has not been studied in the Pacific white shrimp, Litopenaeus vannamei. Therefore, we investigated changes in OA levels, its distribution in regions of the central nervous system (CNS) and ovary during the ovarian maturation cycle, as well as its possible role in regulating ovarian maturation. OA exhibited the highest concentration in the brain and thoracic ganglia at ovarian stage II, and then declined to the lowest concentration at ovarian stages III and IV. In the cerebral ganglia, OA-immunoreactivity (OA-ir) was present in neurons of clusters 6, 17, the anterior and posterior medial protocerebral, olfactory, antenna II, and tegumentary neuropils. In the circumesophageal, subesophageal, thoracic ganglia and abdominal ganglia, OA-ir was detected in several neuropils, neurons and fibers. The high level of intensity in OA immunostaining was observed in early developmental stage of oocyte by comparison with low level of OA-ir in late stages of oocyte development. Functionally, OA-injected female shrimps at doses of 2.5×10(-7) and 2.5×10(-6)mol/shrimp, showed significantly decreased gonado-somatic indices, oocyte diameters, and hemolymph vitellogenin levels, compared with control groups. This study showed changes of OA in the CNS and ovary reaching the highest level in early ovarian stages and declining in late stages, and it decreased hemolymph vitellogenin levels, suggesting significant involvement of OA in female reproduction in this species.

Characterization of a prawn OA/TA receptor in Xenopus oocytes suggests functional selectivity between octopamine and tyramine

Here we report the characterization of an octopamine/tyramine (OA/TA or TyrR1) receptor (OA/TA_Mac) cloned from the freshwater prawn, Macrobrachium rosenbergii, an animal used in the study of agonistic social behavior. The invertebrate OA/TA receptors are seven trans-membrane domain G-protein coupled receptors that are related to vertebrate adrenergic receptors. Behavioral studies in arthropods indicate that octopaminergic signaling systems modulate fight or flight behaviors with octopamine and/or tyramine functioning in a similar way to the adrenalins in vertebrate systems. Despite the importance of octopamine signaling in behavioral studies of decapod crustaceans there are no functional data available for any of their octopamine or tyramine receptors. We expressed OA/TA_Mac in Xenopus oocytes where agonist-evoked trans-membrane currents were used as readouts of receptor activity. The currents were most effectively evoked by tyramine but were also evoked by octopamine and dopamine. They were effectively blocked by yohimbine. The electrophysiological approach we used enabled the continuous observation of complex dynamics over time. Using voltage steps, we were able to simultaneously resolve two types of endogenous currents that are affected over different time scales. At higher concentrations we observe that octopamine and tyramine can produce different and opposing effects on both of these currents, presumably through the activity of the single expressed receptor type. The pharmacological profile and apparent functional-selectivity are consistent with properties first observed in the OA/TA receptor from the insect Drosophila melanogaster. As the first functional data reported for any crustacean OA/TA receptor, these results suggest that functional-selectivity between tyramine and octopamine is a feature of this receptor type that may be conserved among arthropods.

Physiological functions and pharmacological and toxicological effects of p-octopamine

p-Octopamine occurs naturally in plants, invertebrates and animals with diverse functions and effects. This review summarizes the chemistry, metabolism, receptor binding characteristics, known physiological functions, and pharmacological and toxicological effects of p-octopamine. Databases used included PubMed and Google Scholar Advanced. p-Octopamine binds to neuroreceptors in insects that are not present in humans, while exhibiting poor binding to α-1, α-2, β-1, and β-2 adrenergic receptors in mammalian systems. p-Octopamine modestly binds to β-3 adrenergic receptors and may therefore promote lipolysis and weight loss. p-Octopamine is produced in brain and nerve tissues of mammals and is present and can be measured in the blood of normal human subjects. p-Octopamine is considered to be a CNS stimulant in spite of the fact that it binds poorly to adrenergic receptors. Variations occur in blood levels in association with neurological and hepatic diseases. Its precise role in normal neurophysiology is unclear. No human studies have been reported that demonstrate adverse cardiovascular effects following oral administration. No human studies have examined the effects of p-octopamine on athletic performance or weight loss and weight management. A need exists for both animal and human safety and efficacy studies involving oral administration of p-octopamine.