Cloning, characterization, and developmental expression of a putative farnesoic acid O-methyl transferase in the female edible crab Cancer pagurus

Sesquiterpenoid pathway in the mandibular organ of Penaeus monodon: Cloning, expression, characterization of PmJHAMT and its alteration response to eyestalk ablation

Methyl farnesoate (MF), a crustacean equivalent of juvenile hormone (JH) of insects, is known to be produced from the mandibular organ (MO). This study reports transcriptome analysis of Penaeus monodon MO and identifies putative genes encoding enzymes in the sesquiterpenoid pathway. A total of 44,490,420 clean reads were obtained and utilized for subsequent analysis. De novo assembly created 31,201 transcripts and 31,167 unigenes. To archive the functional annotation, all unigenes were annotated with KOG, KEGG, and GO. Putative genes encoding enzymes and regulatory proteins involved in the sesquiterpenoid pathway were obtained from the MO transcriptome data based on the conserved domains and sequence homology. They included S-adenosylmethionine synthetase, farnesyl pyrophosphate synthase, short chain dependent dehydrogenase/reductase (SDR), NAD(P) + -dependent aldehyde dehydrogenase, S-adenosylmethionine-dependent methyltransferases or juvenile hormone acid-O-methyl transferase (JHAMT), farnesoic acid O-methyl transferase (FAMeT), juvenile hormone binding protein, cytochrome C/P-450 family 15 (CRYP15A1)/methylfarnesoate epoxidase (MFE), juvenile hormone epoxide hydrolase (JHEH), and juvenile hormone esterase (JHE). We first identified and characterized JHAMT orthologs inP. monodon(PmJHAMT). The complete cDNA sequence ofPmJHAMTconsisted of 1,221 nt encoded 271 amino acids with a conserved S-adenosyl methionine (SAM) binding domain. Phylogenetic analysis clusteredPmJHAMTinto the group JHAMT with the same clade of the crabPortunus trituberculausJHAMT. Moreover, the predicted three-dimensional structure of PmJHAMT showed remarkable similarity with the recent crystal structure ofthe Bombyx moriJHAMT homodimer. RT-PCR analysis revealed that PmJHAMT was exclusively expressed in MO and initially expressed at stage 3 postlarvae. In situ hybridization with a specific probe to PmJHAMT validated the specific expression of this gene in MO cells. Finally, we evaluated the regulation of MO by eyestalk inhibitory peptides. Diminishing MO inhibitory hormone through unilateral eyestalk ablation resulted in a significantly higher expression ofPmJHAMTin MO by quantitative PCR. This result indicated that the eyestalk inhibitory hormone inhibited MF synthesis byPmJHAMTgene suppression in the MO. This finding provides insight into the crustacean sesquiterpenoid pathway and improves our understanding of crustacean endocrinology.

Identification and Evolution Analysis of the Complete Methyl Farnesoate Biosynthesis and Related Pathway Genes in the Mud Crab, Scylla paramamosain

The sesquiterpenoid hormone methyl farnesoate (MF) plays a vital role during crustacean development, which is mainly evidenced by its varied titers during different developmental stages. However, the biosynthesis pathways of MF remain obscure to some extent. In this study, we identified the complete MF biosynthesis and related pathway genes in Scylla paramamosain, including three involved in acetyl-CoA metabolism, eight in the mevalonate pathway, five in the sesquiterpenoids synthesis pathway, and five in the methionine cycle pathway. Bioinformatics, genomic structure, and phylogenetic analysis indicated that the JH biosynthesis genes might have experienced evolution after species differentiation. The mRNA tissue distribution analysis revealed that almost all genes involving in or relating to MF syntheses were highly expressed in the mandibular organ (MO), among which juvenile hormone acid methyltransferase was exclusively expressed in the MO, suggesting that most of these genes might mainly function in MF biosynthesis and that the methionine cycle pathway genes might play a crucial regulatory role during MF synthesis. In addition, the phylogenetic and tissue distribution analysis of the cytochrome P450 CYP15-like gene suggested that the epoxidized JHs might exist in crustaceans, but are mainly synthesized in hepatopancreas rather than the MO. Finally, we also found that betaine-homocysteine S-methyltransferase genes were lost in insects while methionine synthase was probably lost in most insects except Folsomia candida, indicating a regulatory discrepancy in the methionine cycle between crustaceans and insects. This study might increase our understanding of synthetic metabolism tailored for sesquiterpenoid hormones in S. paramamosain and other closely related species.

Cloning, expression analysis and RNAi of farnesoic acid O-methylransferase gene from Neocaridina denticulata sinensis

Methyl farnesoate (MF) is an essential endocrine hormone in crustaceans, which can promote the occurrence of crustaceans molting, control morphogenesis, affect gonad development, and regulate the stress stimulation to the external environment. The farnesoic acid O-methyltransferase (FAMeT) is a key rate-limiting enzyme in MF synthesis, catalyzing the conversion of farnesoic acid (FA) into MF. Neocaridina denticulata sinensis [Decapoda] is a suitable animal model for studying crustaceans because it can reproduce many times under artificial control and has a short reproductive cycle. According to its transcriptomic and genomic information, the full-length cDNA sequence of FAMeT from N. denticulata sinensis (NdFAMeT) was cloned and the characterization of its deduced amino acid sequence was also analyzed. The relative expression of NdFAMeT in different tissues was determined. The NdFAMeT protein was recombinantly expressed in E. coli and its enzyme activity was determined. After gene knockdown by RNAi technology, the protein activity of shrimp was decreased and the individual phenotype was also observed.

Juvenile hormone synthesis and signaling disruption triggering male offspring induction and population decline in cladocerans (water flea): Review and adverse outcome pathway development

Juvenile hormone (JH) are a family of multifunctional hormones regulating larval development, molting, metamorphosis, reproduction, and phenotypic plasticity in arthropods. Based on its importance in arthropod life histories, many insect growth regulators (IGRs) mimicking JH have been designed to control harmful insects in agriculture and aquaculture. These JH analogs (JHAs) may also pose hazards to nontarget species by causing unexpected endocrine-disrupting (ED) effects such as molting and metamorphosis defects, larval lethality, and disruption of the sexual identity. This critical review summarizes the current knowledge of the JH-mediated effects in the freshwater cladoceran crustaceans such as Daphnia species on JHA-triggered endocrine disruptive outputs to establish a systematic understanding of JHA effects. Based on the current knowledge, adverse outcome pathways (AOPs) addressing the JHA-mediated ED effects in cladoceran leading to male offspring production and subsequent population decline were developed. The weight of evidence (WoE) of AOPs was assessed according to established guidelines. The review and AOP development aim to present the current scientific understanding of the JH pathway and provide a robust reference for the development of tiered testing strategies and new risk assessment approaches for JHAs in future ecotoxicological research and regulatory processes.

Molecular evidence for farnesoic acid O-methyltransferase (FAMeT) involved in the biosynthesis of vitellogenin in the Chinese mitten crab Eriocheir sinensis

Sesquiterpenoid methyl farnesoate (MF), a crustacean equivalent of insect juvenile hormone (JH III), has essential functions in regulating physiological processes in crustaceans, including reproduction and vitellogenesis. Farnesoic acid O-methyltransferase (FAMeT) is a key rate-limiting enzyme catalyzing the conversion of farnesoic acid (FA) to JH/MF in insects and crustaceans. In this study, a full-length cDNA of EsFAMeT from Eriocheir sinensis was isolated and characterized. The deduced EsFAMeT amino acid sequence indicated there were two conserved Methyltransf-FA domains characteristic of FAMeT family proteins. With use of sequence alignment analysis procedures, there was an indication that FAMeT proteins are highly conserved among crustaceans and FAMeT is more closely related to crustacean FAMeT than to insect FAMeT. Results from quantitative real-time PCR analysis revealed there was ubiquitous EsFAMeT in all tissues examined, with greater abundances of mRNA transcripts in the ovary. The transcription of EsFAMeT indicated there were stage-specific patterns in the hepatopancreas and ovary during ovarian development, with the greatest abundance during ovarian development Stages II and III, respectively. To investigate functions of EsFAMeT in vitellogenin biosynthesis in E. sinensis, RNA interference-mediated gene knockdown was used in vitro and in vivo. Injection of EsFAMeT dsRNA resulted in a marked decrease in EsVg (encoding vitellogenin) transcripts in the ovary and hepatopancreas both in vitro and in vivo. Results from the present study indicated EsFAMeT is involved in vitellogenin biosynthesis in the ovary and hepatopancreas of E. sinensis, providing a new resource to study modulatory effects of the FAMeT family of enzymes in crustacean reproduction.

Characterization and expression profile of farnesoic acid O-methyltransferase gene from Indian white shrimp, Penaeus indicus

Methyl farnesoate (MF), a sesquiterpenoid synthesized in the mandibular organ, regulates many physiological processes in crustaceans including growth and reproduction. In the present study, farnesoic acid O-methyltransferase (FAMeT), the key enzyme responsible for final step conversion of farnesoic acid (FA) to methyl farnesoate (MF), was cloned and characterized from the nervous tissues of Penaeus indicus. Multiple sequence alignment, prediction of conserved domain regions, phosphorylation sites identification and phylogenetic analysis indicated that putative FAMeT fragment from P. indicus (PiFAMeT), shares a high degree of sequence identity to FAMeT proteins isolated from other crustaceans species. Quantitative real-time PCR analysis revealed ubiquitous expression of PiFAMeT in all the tissues examined, with comparative higher mRNA levels in nervous tissue and ovary. Additionally, the levels of PiFAMeT also showed gradual increase of expression correlating with the advancement in ovarian maturation. Further to support their role in promoting ovarian development, serotonin treatment (5HT, 50 μg/g body weight) was given to eyestalk intact and unilaterally eyestalk ablated females which resulted in significant increase in PiFAMeT transcript levels at day 7 and day 14. The relatively higher levels of PiFAMeT, reflecting higher levels of MF, suggest a role during secondary vitellogenesis thereby regulating ovarian development in P. indicus. Further research is required to understand the synergistic interaction of MF pathways with serotonergic and other regulatory pathways in regulating ovarian maturation in penaeid shrimps.

Transcriptional and Translational Relationship in Environmental Stress: RNAseq and ITRAQ Proteomic Analysis Between Sexually Reproducing and Parthenogenetic Females in Moina micrura

Moina micrura is a kind of small-bodied water flea within the family Moinidae. Similar to Daphnia, M. micrura could also switch its reproduction mode from parthenogenetic female (PF) to sexual female (SF) to adapt to the external environment. To uncover the mechanisms of reproductive switching in M. micrura, we used both RNA-Seq and iTRAQ analyses to investigate the differentially expressed genes (DEGs) and their protein products between SF and PF in M. micrura. A total of 1665 DEGs (702 up-regulated, 963 down-regulated) and 600 differentially expressed proteins (DEPs) (102 up-regulated, 498 down-regulated) were detected in SF. Correlation analyses indicated that 31 genes were expressed significantly differentially at both transcriptomic and proteomic levels, including 15 up-regulated genes and 16 down-regulated genes in SF. Meanwhile, our data also showed that 528 DEPs have discordant expression at transcript level, implying post-transcriptional (including translational) regulation. These top up-regulated genes and their protein products in SF were mainly grouped into the globin-related family, vitellogenin-related family, cuticle-related family, Hsp-related family and methyltransferases-related family, which were all involved in the reproductive switching in Daphnia. In contrast, a cluster of orthologous groups revealed that up-regulated genes and their protein products in PF were strongly associated with the metabolic process, which may be responsible for rapid population proliferation in M. micrura.

Transcriptomic information from Pacific white shrimp (Litopenaeus vannamei) ovary and eyestalk, and expression patterns for genes putatively involved in the reproductive process

The increased use of massive sequencing technologies has enabled the identification of several genes known to be involved in different mechanisms associated with reproduction that so far have only been studied in vertebrates and other model invertebrate species. In order to further investigate the genes involved in Litopenaeus vannamei reproduction, cDNA and SSH libraries derived from female eyestalk and gonad were produced, allowing the identification of expressed sequences tags (ESTs) that potentially have a role in the regulation of gonadal maturation. In the present study, different transcripts involved in reproduction were identified and a number of them were characterized as full-length. These transcripts were evaluated in males and females in order to establish their tissue expression profiles during developmental stages (juvenile, subadult and adult), and in the case of females, their possible association with gonad maturation was assessed through expression analysis of vitellogenin. The results indicated that the expression of vitellogenin receptor (vtgr) and minichromosome maintenance (mcm) family members in the female gonad suggest an important role during previtellogenesis. Additionally, the expression profiles of genes such as famet, igfbp and gpcr in brain tissues suggest an interaction between the insulin/insulin-like growth factor signaling pathway (IIS) and methyl farnesoate (MF) biosynthesis for control of reproduction. Furthermore, the specific expression pattern of farnesoic acid O-methyltransferase suggests that final synthesis of MF is carried out in different target tissues, where it is regulated by esterase enzymes under a tissue-specific hormonal control. Finally, the presence of a vertebrate type steroid receptor in hepatopancreas and intestine besides being highly expressed in female gonads, suggest a role of that receptor during sexual maturation.

Hemolymph Levels of Methyl Farnesoate During Ovarian Development of the Swimming Crab Portunus trituberculatus, and Its Relation to Transcript Levels of HMG-CoA Reductase and Farnesoic Acid O-Methyltransferase

Methyl farnesoate (MF) is a sesquiterpene compound and the crustacean homolog of insect juvenile hormones. MF has multiple physiological functions involving the regulation of molting, reproduction, metamorphogenesis, behavior, and osmoregulation. In this study, the hemolymph levels of MF during ovarian development of Portunus trituberculatus were measured by gas chromatography-mass spectrometry (GC-MS). The results showed that the hemolymph level of MF in P. trituberculatus was low during stages I and II, increased considerably in stage III, and remained high in stage IV. Correlation of MF level with ovarian maturation indicates the putative stimulatory role of MF in this physiological process. As 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGR) and farnesoic acid O-methyltransferase (FAMeT) are two essential enzymes in MF biosynthesis, their transcript levels during ovarian development were detected by quantitative real-time PCR (qPCR). Transcript levels of HMGR and FAMeT exhibited variation trends similar to that of the level of MF in hemolymph. This might indicate that high expression of HMGR and FAMeT could result in an increase in the production of MF, which ultimately affects ovarian development.

Cloning and expressing a highly functional and substrate specific farnesoic acid o-methyltransferase from the Asian citrus psyllid (Diaphorina citri Kuwayama)

The Asian citrus psyllid, Diaphorina citri, transmits a phloem-limited bacterium, Candidatus 'Liberibacter' asiaticus that causes citrus greening disease. Because juvenile hormone (JH) plays an important role in adult and nymphal development, we studied the final steps in JH biosynthesis in D. citri. A putative JH acid methyltransferase ortholog gene (jmtD) and its cognate cDNA were identified by searching D. citri genome database. Expression analysis shows expression in all life stages. In adults, it is expressed in the head-thorax, (containing the corpora allata), and the abdomen (containing ovaries and male accessory glands). A 3D protein model identified the catalytic groove with catalytically active amino acids and the S-adenosyl methionine (SAM)-binding loop. The cDNA was expressed in Escherichia coli cells and the purified enzyme showed high preference for farnesoic acid (FA) and homoFA (kcat of 0.752 × 10(-3) and 0.217 × 10(-3) s(-1), respectively) as compared to JH acid I (JHA I) (cis/trans/cis; 2Z, 6E, 10cis), JHA III (2E, 6E, 10cis), and JHA I (trans/cis/cis; 2E, 2Z, 10cis) (kcat of 0.081 × 10(-3), 0.013 × 10(-3), and 0.003 × 10(-3) s(-1), respectively). This suggests that this ortholog is a DcFA-o-methyl transferase gene (fmtD), not a jmtD, and that JH biosynthesis in D. citri proceeds from FA to JH III through methyl farnesoate (MF). DcFA-o-MT does not require Ca(2+), Mg(2+) or Zn(2+), however, Zn(2+) (1 mM) completely inhibits the enzyme probably by binding H115 at the active groove. This represents the first purified FA-o-MT from Hemiptera with preferred biological activity for FA and not JHA.

The proteomic response of cheliped myofibril tissue in the eurythermal porcelain crab Petrolisthes cinctipes to heat shock following acclimation to daily temperature fluctuations

The porcelain crab Petrolisthes cinctipes lives under rocks and in mussel beds in the mid-intertidal zone where it experiences immersion during high tide and saturating humid conditions in air during low tide, which can increase habitat temperature by up to 20°C. To identify the biochemical changes affected by increasing temperature fluctuations and subsequent heat shock, we acclimated P. cinctipes for 30 days to one of three temperature regimes: (1) constant 10°C, (2) daily temperature fluctuations between 10 and 20°C (5 h up-ramp to 20°C, 1 h down-ramp to 10°C) and (3) 10–30°C (up-ramp to 30°C). After acclimation, animals were exposed to either 10°C or a 30°C heat shock to analyze the proteomic changes in claw muscle tissue. Following acclimation to 10–30°C (measured at 10°C), enolase and ATP synthase increased in abundance. Following heat shock, isoforms of arginine kinase and glycolytic enzymes such as aldolase, triose phosphate isomerase and glyceraldehyde 3-phosphate dehydrogenase increased across all acclimation regimes. Full-length isoforms of hemocyanin increased abundance following acclimation to 10–30°C, but hemocyanin fragments increased after heat shock following constant 10°C and fluctuating 10–20°C, possibly playing a role as antimicrobial peptides. Following constant 10°C and fluctuating 10–20°C, paramyosin and myosin heavy chain type-B increased in abundance, respectively, whereas myosin light and heavy chain decreased with heat shock. Actin-binding proteins, which stabilize actin filaments (filamin and tropomyosin), increased during heat shock following 10–30°C; however, actin severing and depolymerization proteins (gelsolin and cofilin) increased during heat shock following 10–20°C, possibly promoting muscle fiber restructuring. RAF kinase inhibitor protein and prostaglandin reductase increased during heat shock following constant 10°C and fluctuating 10–20°C, possibly inhibiting an immune response during heat shock. The results suggest that ATP supply, muscle fiber restructuring and immune responses are all affected by temperature fluctuations and subsequent acute heat shock in muscle tissue. Furthermore, although heat shock after acclimation to constant 10°C and fluctuating 10–30°C showed the greatest effects on the proteome, moderately fluctuating temperatures (10–20°C) broadened the temperature range over which claw muscle was able to respond to an acute heat shock with limited changes in the muscle proteome.

A farnesoic acid O-methyltransferase (FAMeT) from Exopalaemon carinicauda is responsive to Vibrio anguillarum and WSSV challenge

Methyl farnesoate (MF), an analogue of the insect juvenile hormone III, is believed to play important roles in the regulation of the growth and reproductive development in crustaceans. Farnesoic acid O-methyltransferase (FAMeT) is the key enzyme in the juvenile hormone biosynthetic pathway, involved in the conversion of farnesoic acid (FA) to MF in the final step of MF synthesis. In this study, a FAMeT cDNA (named EcFAMeT) was cloned from the hemocytes of ridgetail white prawn Exopalaemon carinicauda by rapid amplification of cDNA ends (RACE) methods. The full-length cDNA of EcFAMeT was 1,620 bp, including contains a 5'-untranslated region (UTR) of 75 bp, 3'-UTR of 714 bp with a poly (A) tail, an open reading frame (ORF) of 831 bp, encoding a 276-amino-acid polypeptide with the predicted molecular weight of 31.57 kDa and estimated isoelectric point of 4.67. BLAST analysis revealed that amino acids of EcFAMeT shared high identity (75-90 %) with that of other crustaceans. Two conserved signatures domains of Methyltransf-FA superfamily were also identified in EcFAMeT. Real time quantitative RT-PCR analysis indicated that EcFAMeT could be detected in all the tested tissues and strongly expressed in hepatopancreas and ovary of E. carinicauda. After Vibrio anguillarum and WSSV challenge, EcFAMeT transcripts both in hemocytes and hepatopancreas increased significantly in the first 3 h, respectively. The results indicated that EcFAMeT might be associated with the immune defenses to V. anguillarum and WSSV in E. carinicauda.

Identification of relevant cancer related-genes in the flat oyster Ostrea edulis affected by disseminated neoplasia

Disseminated neoplasia (DN), an oyster disease resembling leukaemia, has been reported in a number of species of marine bivalve molluscs. The disease is characterised by a proliferation of abnormal circulating cells of unknown origin resulting in the invasion of tissues and organs, frequently with a fatal end of the affected individuals. To obtain a more comprehensive view of bivalve cancer processes, suppressive subtracted hybridisation (SSH) and quantitative RT-PCR (q-PCR) approaches were combined to investigate changes in the transcriptome of Ostrea edulis haemolymph cells associated to DN. Two SSH libraries were constructed and 587 expressed sequence tags (ESTs) were sequenced, obtaining 329 ESTs which showed expression changes in neoplastic process. Transcription expression analyses (q-PCR) were done for a total of 24 genes that could be relevant in neoplastic process, including genes with role in the regulation of cell cycle, apoptosis or chromosomal defects. Most of those genes had not been reported in association with cancer in non-vertebrate organisms. The over-expression and under-expression of some of those genes in DN-affected oysters was in agreement with observations in vertebrate cancer. The results herein reported contribute to cancer understanding in bivalve molluscs.

Identification, cloning and expression analysis of Catechol-O-methyltransferase (COMT) gene from shrimp, Penaeus monodon and its relevance to salinity stress

O-methyltransferase (OMT), a protein present ubiquitously in wide range of organisms plays significant role in methylation of small macro molecules for various functional and regulatory purposes. In crustaceans, OMT has functional role in growth, reproduction, ovarian development and molting. In the present study, suppression subtractive hybridization (SSH) performed using gill tissues of low (3ppt) and high (55ppt) salinity stressed shrimp Penaeus monodon resulted in identification of differentially expressed genes involved in signal transduction pathways, metabolism, defense proteins, DNA repair and synthesis, apoptosis, cell cycle regulation along with unknown and hypothetical proteins. Catechol-O-methyltransferase (COMT) a type of OMT was identified by SSH as one of the differentially expressed genes of shrimp P. monodon subjected to low and high salinity stress. The full length cDNA of COMT was cloned from the gills of P. monodon which consisted an open reading frame of 666 bp, encoding 221 amino acids. The ORF revealed one each of N-glycosylation and O-glycosylation sites and nine phosphorylation sites. The deduced amino acid sequence of COMT exhibited high sequence identity (92%) with COMT class of protein from Fenneropenaeus chinensis. Real time PCR analysis of the shrimp samples exposed to low salinity conditions at 3ppt revealed significant increase in expression of COMT transcripts in the guts at 24 h, 48 h, 1 week and 2 weeks, gills at 24 h and in the muscle tissues at 48 h, with maximum expression of the COMT levels by 5 fold in guts (1 week), 1 fold in gills (24 h) and 1.5 fold in muscle (48 h) respectively. The increased expression level of COMT at different time intervals in different tissues suggests a possible role of this gene in salinity stress tolerance in shrimps under low salinity conditions.

Transcriptomics of a giant freshwater prawn (Macrobrachium rosenbergii): de novo assembly, annotation and marker discovery

BACKGROUND

Giant freshwater prawn (Macrobrachium rosenbergii or GFP), is the most economically important freshwater crustacean species. However, as little is known about its genome, 454 pyrosequencing of cDNA was undertaken to characterise its transcriptome and identify genes important for growth.

METHODOLOGY AND PRINCIPAL FINDINGS

A collection of 787,731 sequence reads (244.37 Mb) obtained from 454 pyrosequencing analysis of cDNA prepared from muscle, ovary and testis tissues taken from 18 adult prawns was assembled into 123,534 expressed sequence tags (ESTs). Of these, 46% of the 8,411 contigs and 19% of 115,123 singletons possessed high similarity to sequences in the GenBank non-redundant database, with most significant (E value < 1e(-5)) contig (80%) and singleton (84%) matches occurring with crustacean and insect sequences. KEGG analysis of the contig open reading frames identified putative members of several biological pathways potentially important for growth. The top InterProScan domains detected included RNA recognition motifs, serine/threonine-protein kinase-like domains, actin-like families, and zinc finger domains. Transcripts derived from genes such as actin, myosin heavy and light chain, tropomyosin and troponin with fundamental roles in muscle development and construction were abundant. Amongst the contigs, 834 single nucleotide polymorphisms, 1198 indels and 658 simple sequence repeats motifs were also identified.

CONCLUSIONS

The M. rosenbergii transcriptome data reported here should provide an invaluable resource for improving our understanding of this species' genome structure and biology. The data will also instruct future functional studies to manipulate or select for genes influencing growth that should find practical applications in aquaculture breeding programs.

Final steps in juvenile hormone biosynthesis in the desert locust, Schistocerca gregaria

Two genes coding for enzymes previously reported to be involved in the final steps of juvenile hormone (JH) biosynthesis in different insect species, were characterised in the desert locust, Schistocerca gregaria. Juvenile hormone acid O-methyltransferase (JHAMT) was previously described to catalyse the conversion of farnesoic acid (FA) and JH acid to their methyl esters, methyl farnesoate (MF) and JH respectively. A second gene, CYP15A1 was reported to encode a cytochrome P450 enzyme responsible for the epoxidation of MF to JH. Additionally, a third gene, FAMeT (originally reported to encode a farnesoic acid methyltransferase) was included in this study. Using q-RT-PCR, all three genes (JHAMT, CYP15A1 and FAMeT) were found to be primarily expressed in the CA of the desert locust, the main biosynthetic tissue of JH. An RNA interference approach was used to verify the orthologous function of these genes in S. gregaria. Knockdown of the three genes in adult animals followed by the radiochemical assay (RCA) for JH biosynthesis and release showed that SgJHAMT and SgCYP15A1 are responsible for synthesis of MF and JH respectively. Our experiments did not show any involvement of SgFAMeT in JH biosynthesis in the desert locust. Effective and selective inhibitors of SgJHAMT and SgCYP15A1 would likely represent selective biorational locust control agents.

Reproductive regulators in decapod crustaceans: an overview

Control of reproductive development in crustaceans requires neuropeptides, ecdysone and methyl farnesoate (MF). A major source of neuropeptides is the X-organ-sinus gland (XO-SG) complex located in the eyestalk ganglia of crustaceans. The other regulatory factors (either peptides or neuromodulators) are produced in the brain and thoracic ganglia (TG). Two other regulatory non-peptide compounds, the steroid ecdysone and the sesquiterpene MF, are produced by the Y-organs and the mandibular organs, respectively. In the current review, I have tried to recapitulate recent studies on the role of gonadal regulatory factors in regulating crustacean reproduction.

The putative-farnesoic acid O-methyl transferase (FAMeT) gene of Ceratitis capitata: characterization and pre-imaginal life expression

Farnesoic acid O-methyl transferase (FAMeT) is the enzyme involved in the penultimate step of insect juvenile hormone (JH) biosynthesis and is thus a key regulator in insect development and reproduction. We report the characterization of the putative-FAMeT in the medfly or Mediterranean fruit fly, Ceratitis capitata. This gene was identified by suppressive subtractive hybridization and completely sequenced by the screening of a medfly cDNA library. The obtained sequence was analyzed for conserved protein domain identification and its expression profile was evaluated by quantitative Real-Time PCR in medfly pre-imaginal life. The tissue expression of the isolated gene was verified by in situ hybridization on third instar larvae sections. The characterization of the isolated gene pointed out several typical features of methyl transferase genes. The pre-imaginal putative-FAMeT expression levels were consistent with JH titer change in Diptera. As recognized in some crustaceans, this gene seems to be widely expressed in the medfly as well. Ceratitis capitata is one of the most relevant agricultural pests against which insecticides and the sterile insect technique (SIT) are extensively used in spite of the well-known limitations of these approaches. Although results are not conclusive for the physiological role of the isolated gene, they suggest the characterization of a new gene in the Mediterranean fruit fly potentially involved in JH biosynthesis and may, therefore, have implications for pest control.

Farnesoic acid O-methyl transferase (FAMeT) isoforms: conserved traits and gene expression patterns related to caste differentiation in the stingless bee, Melipona scutellaris

Farnesoic acid O-methyl transferase (FAMeT) is the enzyme that catalyzes the formation of methyl farnesoate (MF) from farnesoic acid (FA) in the biosynthetic pathway of juvenile hormone (JH). This work reports the cloning, sequencing, and expression of FAMeT gene from the stingless bee Melipona scutellaris (MsFAMeT). The MsFAMeT in silico analysis showed that greatest sequence similarity is found in Apis mellifera and other insects, while relatively less similarity is shown in crustaceans. Evidence of alternative splicing of a 27 nucleotide (nt) microexon explains the presence of the detected isoforms, 1 and 2. The expression analysis of the two isoforms showed a marked difference when castes were compared, suggesting that they could be involved differently in the JH metabolism in M. scutellaris, providing new insights for the comprehension of female plasticity.

A putative farnesoic acid O-methyltransferase (FAMeT) orthologue in Drosophila melanogaster (CG10527): relationship to juvenile hormone biosynthesis?

Juvenile hormones (JHs) are key regulators of both metamorphosis and adult reproductive processes. Farnesoic acid O-methyltransferase (FAMeT) is thought to be an important enzyme in the JH biosynthetic pathway, catalyzing methylation of farnesoic acid (FA) to methyl farnesoate (MF). Previous evidence in other insects suggested that FAMeT is rate limiting and regulated by a neuropeptide family, the allatostatins. A full-length cDNA encoding a 296 amino acid putative FAMeT has been isolated. A recombinant (r)FAMeT was cloned, expressed and a specific antiserum generated. rFAMeT was assayed for enzymatic activity using a radiochemical assay. In this assay, no activity was detected either with rFAMeT alone or when added to a corpus allatum CA extract. Immunohistochemical analysis was used to confirm the presence of FAMeT in the CA of Drosophila melanogaster ring gland. Analysis of MF, JHIII and JHB3 release in wild type and mutant stocks in the presence and absence of Drome AST (PISCF-type) suggest that Drosophila FAMeT has little if any effect on sesquiterpenoid biosynthesis. Drome AST appears to have a select effect on JH bisepoxide biosynthesis and not MF or JHIII. Additional analysis of MF, JHIII and JHB3 release in strains with a deficiency or decrease of FAMeT compared to wild type shows no significant decrease in MF, JHIII or JH bisepoxide synthesis. Deficiency strains that reduce the level of FAMeT showed reduced longevity relative to wildtype but this result may be due to other genetic influences.

Characterization of the putative farnesoic acid O-methyltransferase (LvFAMeT) cDNA from white shrimp, Litopenaeus vannamei: Evidence for its role in molting

Methyl farnesoate (MF) is the crustacean homolog of the insect juvenile hormone and is believed to regulate growth and reproduction in crustaceans. Farnesoic acid O-methyltransferase (FAMeT) catalyzes the conversion of farnesoic acid (FA) to MF. Here we report the cloning and characterization of two forms of FAMeTs (i.e. LvFAMeT-S and LvFAMeT-L) from the shrimp Litopenaeus vannamei. LvFAMeT transcript has a wide tissue distribution pattern in L. vannamei and is also expressed in nauplius, zoea, mysis, post-larval stages and adults. Unlike FAMeTs reported in other decapods, transcripts of two different sizes were detected in L. vannamei. We postulate that the wide distribution of LvFAMeT expression may be related to its role in growth and regulation of molting. To study the functions of LvFAMeT in molting, the RNA interference (RNAi) technique was used. Injection of double stranded RNA (dsRNA) for LvFAMeT knocked down the expression of LvFAMeT in shrimp for at least 3 days and the shrimp did not advance to the final stage of molt cycle. Furthermore, the expression of the molt-related genes encoding cathepsin-L and the hemocyanin gene was disturbed. Subsequently, 100% mortality of the shrimp was observed in the LvFAMeT dsRNA-injected shrimp. In contrast, control shrimp completed their molt and proceeded to the next molt cycle. We postulate that, as an important enzyme for the conversion of FA to MF, RNAi injection knocked down the expression of LvFAMeT which could potentially result in a decrease in the production of MF and subsequently, could affect the molting process. The newly identified LvFAMeT may be involved in the control of molting in shrimp. The results of this study demonstrate the potential use of the RNA interference technique to study other putative genes identified in crustaceans.

Isolation and expression analysis of multiple isoforms of putative farnesoic acid O-methyltransferase in several crustacean species

Farnesoic acid O-methyltransferase (FaMeT) is the enzyme responsible for the conversion of farnesoic acid (FA) to methyl farnesoate (MF) in the final step of MF synthesis. Multiple isoforms of putative FaMeT were isolated from six crustacean species belonging to the families Portunidae, Penaeidae, Scyllaridae and Parastacidae. The portunid crabs Portunus pelagicus and Scylla serrata code for three forms: short, intermediate and long. Two isoforms (short and long) were isolated from the penaeid prawns Penaeus monodon and Fenneropenaeus merguiensis. Two isoforms were also identified in the scyllarid Thenus orientalis and parastacid Cherax quadricarinatus. Putative FaMeT sequences were also amplified from the genomic DNA of P. pelagicus and compared to the putative FaMeT transcripts expressed. Each putative FaMeT cDNA isoform was represented in the genomic DNA, indicative of a multi-gene family. Various tissues from P. pelagicus were individually screened for putative FaMeT expression using PCR and fragment analysis. Each tissue type expressed all three isoforms of putative FaMeT irrespective of sex or moult stage. Protein domain analysis revealed the presence of a deduced casein kinase II phosphorylation site present only in the long isoform of putative FaMeT.

Cloning and expression analysis of an o-methyltransferase (OMT) gene from Chinese shrimp, Fenneropenaeus chinensis

O-methyltransferase (OMT) is ubiquitously present in diverse organisms and plays an important regulatory role in plant and animal growth, development, reproduction and defence and has also been implicated in human emotion and disease. A putative o-methyltransferase (OMT) gene has been cloned from the haemocytes of bacteria-infected Chinese shrimp (Fenneropenaeus chinensis) by suppression subtractive hybridisation (SSH) coupled with the SMART cDNA method. The isolated 944 bp full-length cDNA contains a single 666bp open reading frame (ORF) encoding a putative OMT protein of 221 amino acids. The predicted protein has a molecular weight of 24,572.06 Da and a pI of 5.27 as well as ten phosphorylation sites. Northern blot and in situ hybridisation analyses demonstrated that the OMT transcripts were constitutively expressed in tissue of shrimp challenged by bacterial infection and in unchallenged shrimp tissue. Constitutive OMT transcript was found in areas such as haemocytes, heart, hepatopancreas, stomach, gill, intestine and ovary. However, the OMT transcripts were upregulated in hepatopancreas and stomach in challenged shrimp.

The mevalonate pathway and the synthesis of juvenile hormone in insects

The mevalonate pathway in insects has two important peculiarities, the absence of the sterol branch and the synthesis of juvenile hormone (JH), that may have influenced the mechanisms of regulation. The data available on these mechanisms indicate that cholesterol does not play a regulatory role and that JH modulates transcript levels of a number of genes of the mevalonate pathway or can influence the translatability and/or stability of the transcripts themselves. These data suggest that the mevalonate pathway in insects can best be interpreted in terms of coordinated regulation, in which regulators act in parallel to a number of enzymes, as occurs in the cholesterol-driven pathway in vertebrates.