The mechanism of C-20 hydroxylation of alpha-ecdysone in the desert locust, Schistocerca gregaria.
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ABSTRACT:
SUBMITTER: Johnson P
PROVIDER: S-EPMC1183799 | biostudies-other | 1977 Dec
REPOSITORIES: biostudies-other
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Project description:The enzyme catalysing the hydroxylation of ecdysone to 20-hydroxyecdysone, ecdysone 20-mono-oxygenase (EC 1.14.99.22), was investigated in the Malpighian tubules of fifth-instar locusts, Schistocerca gregaria. Enzyme activity was optimal at 35 degrees C and pH 6.8-8.0. Under these conditions the mono-oxygenase exhibited an apparent Km for ecdysone of 7.1 X 10(-7) M, a maximal specific activity of 1.1 nmol/h per mg of protein and was competitively inhibited by 20-hydroxyecdysone with an apparent Ki of 6.3 X 10(-7) M. Enzyme activity was decreased in the presence of Ca2+, Mg2+, EDTA and non-ionic detergents. The Malpighian tubule ecdysone 20-mono-oxygenase was localized primarily in the subcellular fraction sedimenting at 7500 g and, on the basis of marker enzyme profiles, was assigned mainly to the mitochondria. NADPH was required for activity, although addition of NADH together with NADPH had a synergistic effect. NADP+-dependent isocitrate dehydrogenase (EC 1.1.1.42) and an energy-dependent NAD(P) transhydrogenase (EC 1.6.1.1.) appeared to be the major sources of reducing equivalents, with the contribution from the 'malic enzyme' (EC 1.1.1.40) being less important. The monooxygenase was characterized as a cytochrome P-450-containing mixed-function oxidase from the inhibition patterns with metyrapone, CO and cyanide; CO inhibition was reversible with monochromatic light at 450 nm. However, the ecdysone 20-mono-oxygenase shows much lower sensitivity to CO inhibition and to photodissociation of the CO-inhibited complex than do vertebrate cytochrome P-450-dependent hydroxylation systems. The concentration of cytochrome P-450 in the Malpighian tubule mitochondria was 30 pmol/mg of protein. The properties of the mono-oxygenase are discussed in relation to hydroxylation enzymes from other sources.
| S-EPMC1144370 | biostudies-other
Project description:Ecdysteroid hormones influence the development and reproduction of arthropods by binding a heterodimeric complex of nuclear receptors, the ecdysone receptor (EcR) and the retinoid-X-receptor/ultraspiracle (RXR/USP). Here, we report on the in vivo role(s) of the ecdysone receptor complex, SchgrEcR/SchgrRXR, in the female reproductive physiology of a major phytophagous pest insect, i.e. the desert locust, Schistocerca gregaria. Tissue and temporal distribution profiles were analysed during the first gonadotrophic cycle of adult female locusts. RNA interference was used as a reverse genetics tool to investigate the in vivo role of the ecdysone receptor complex in ovarian maturation, oogenesis, fertility and fecundity. We discovered that silencing the ecdysone receptor complex in S. gregaria resulted in impaired ovulation and oviposition, indicative for a crucial role of this complex in chorion formation. We also found evidence for a feedback of SchgrEcR/SchgrRXR on juvenile hormone biosynthesis by the corpora allata. Furthermore, we observed a tissue-dependent effect of the SchgrEcR/SchgrRXR knockdown on the transcript levels of the insulin receptor and neuroparsin 3 and 4. The insulin receptor transcript levels were upregulated in the brain, but not the fat body and gonads. Neuroparsins 3 and 4 transcript levels were down regulated in the brain and fat body, but not in the gonads.
| S-EPMC6327042 | biostudies-literature
Project description:DNA methylation is a widely conserved epigenetic modification that is established and maintained by the cooperative activity of DNA methyltransferases. While the complement of DNA methyltransferase genes can vary substantially between animal species, whole-genome methylation analyses have suggested that major features of animal methylomes are widely conserved. We have now used genome-scale bisulfite sequencing to analyze the methylome of the desert locust, Schistocerca gregaria, which represents an economically important pest with a high degree of phenotypic plasticity. Interestingly, in this system, DNA methylation appears to be both established and maintained by Dnmt1 methyltransferases, which distinguishes locusts from most other known organisms. Our results indicate that the S. gregaria methylome shares preferential methylation of CpG dinucleotides and exons with other animal methylomes. In contrast to other invertebrates, however, overall methylation levels were substantially higher and a significant fraction of transposons was methylated. Additionally, genes were densely methylated in a pronounced bimodal pattern, suggesting a role for DNA methylation in the regulation of locust gene expression. Altogether, our results uncover a unique pattern of genome methylation in locusts and also suggest that animal methylomes may be more diverse than previously thought.
2013-05-03 | GSE41214 | GEO
Project description:The stereochemistry of hydroxylation at C-2 during the biosynthesis of ecdysone in the ovaries of Schistocerca gregaria was investigated by incorporation of [1 alpha,2 alpha-3H(n)]cholesterol in admixture with [4-14C]cholesterol into oöcyte 2-deoxyecdysone and ecdysone conjugates in maturing adult female S. gregaria. Extraction of the eggs followed by enzymic hydrolysis of the ecdysteroid conjugate fraction yielded free ecdysteroids, from which 2-deoxyecdysone and ecdysone were purified. The 3H/14C ratios in the 2-deoxyecdysone and ecdysone were similar, suggesting that the 2 alpha hydrogen of cholesterol was retained during hydroxylation at C-2. This was corroborated by oxidation at C-2 of the 3,22-diacetate derivative of the ecdysone, yielding the corresponding 2-oxo compound with removal of essentially all the 3H originally present at the 2 alpha position of cholesterol. The results indicate that the 2 beta hydrogen of cholesterol has been eliminated during the hydroxylation at C-2. Thus, during ecdysone biosynthesis, hydroxylation at C-2 is direct and occurs with retention of configuration.
| S-EPMC1153282 | biostudies-other
Project description:DNA methylation is a widely conserved epigenetic modification that is established and maintained by the cooperative activity of DNA methyltransferases. While the complement of DNA methyltransferase genes can vary substantially between animal species, whole-genome methylation analyses have suggested that major features of animal methylomes are widely conserved. We have now used genome-scale bisulfite sequencing to analyze the methylome of the desert locust, Schistocerca gregaria, which represents an economically important pest with a high degree of phenotypic plasticity. Interestingly, in this system, DNA methylation appears to be both established and maintained by Dnmt1 methyltransferases, which distinguishes locusts from most other known organisms. Our results indicate that the S. gregaria methylome shares preferential methylation of CpG dinucleotides and exons with other animal methylomes. In contrast to other invertebrates, however, overall methylation levels were substantially higher and a significant fraction of transposons was methylated. Additionally, genes were densely methylated in a pronounced bimodal pattern, suggesting a role for DNA methylation in the regulation of locust gene expression. Altogether, our results uncover a unique pattern of genome methylation in locusts and also suggest that animal methylomes may be more diverse than previously thought. Whole exome methylation analysis of S. gregaria. Two samples were analyzed, one sample containing DNA from brain, one sample containing DNA from MTG. To date, there exists no sequenced genome of Schistocerca gregaria; thus, we could only map the data against an EST database (Locust2 EST project) representing the coding part of the genome.
2013-05-03 | E-GEOD-41214 | biostudies-arrayexpress
Project description:The desert locust Schistocerca gregaria recognizes multiple chemical cues, which are received by olfactory sensory neurons housed in morphologically identifiable sensilla. The different sensillum types contain olfactory sensory neurons with different physiological specificities, i.e., they respond to different categories of chemical signals. The molecular basis for the sensilla-specific responsiveness of these cells is unknown, but probably based on the endogenous receptor repertoire. To explore this issue, attempts were made to elucidate whether distinct odorant receptors (ORs) may be expressed in a sensilla-specific manner. Analyzing more than 80 OR types concerning for a sensilla-specific expression revealed that the vast majority was found to be expressed in sensilla basiconica; whereas only three OR types were expressed in sensilla trichodea. Within a sensillum unit, even in the multicellular assembly of sensilla basiconica, many of the OR types were expressed in only a single cell, however, a few OR types were found to be expressed in a consortium of cells typically arranged in a cluster of 2-4 cells. The notion that the OR-specific cell clusters are successively formed in the course of development was confirmed by comparing the expression patterns in different nymph stages. The results of this study uncover some novel and unique features of locust olfactory system, which will contribute to unravel the complexity of locust olfaction.
| S-EPMC6714038 | biostudies-literature
Project description:Background: At the time of publication, the most devastating desert locust crisis in decades is affecting East Africa, the Arabian Peninsula and South-West Asia. The situation is extremely alarming in East Africa, where Kenya, Ethiopia and Somalia face an unprecedented threat to food security and livelihoods. Most of the time, however, locusts do not occur in swarms, but live as relatively harmless solitary insects. The phenotypically distinct solitarious and gregarious locust phases differ markedly in many aspects of behaviour, physiology and morphology, making them an excellent model to study how environmental factors shape behaviour and development. A better understanding of the extreme phenotypic plasticity in desert locusts will offer new, more environmentally sustainable ways of fighting devastating swarms. Methods: High molecular weight DNA derived from two adult males was used for Mate Pair and Paired End Illumina sequencing and PacBio sequencing. A reliable reference genome of Schistocerca gregaria was assembled using the ABySS pipeline, scaffolding was improved using LINKS. Results: In total, 1,316 Gb Illumina reads and 112 Gb PacBio reads were produced and assembled. The resulting draft genome consists of 8,817,834,205 bp organised in 955,015 scaffolds with an N50 of 157,705 bp, making the desert locust genome the largest insect genome sequenced and assembled to date. In total, 18,815 protein-encoding genes are predicted in the desert locust genome, of which 13,646 (72.53%) obtained at least one functional assignment based on similarity to known proteins. Conclusions: The desert locust genome data will contribute greatly to studies of phenotypic plasticity, physiology, neurobiology, molecular ecology, evolutionary genetics and comparative genomics, and will promote the desert locust's use as a model system. The data will also facilitate the development of novel, more sustainable strategies for preventing or combating swarms of these infamous insects.
| S-EPMC7607483 | biostudies-literature
Project description:The locust genus Schistocerca (Stål) has a transatlantic disjunction, which has been controversial for more than a century. Among 50 species within the genus, only one species, the desert locust (S. gregaria Forskål), occurs in the Old World, and the rest occur in the New World. Earlier taxonomists suggested that the desert locust is a migrant from America, but this view was strongly challenged when a large swarm of the desert locust successfully crossed the Atlantic Ocean from West Africa to the West Indies in 1988. The currently accepted view, supported by this incident, is that the New World species are descendants of a gregaria-like ancestor, and the desert locust would be ancestral to the rest of the genus. However, there is surprisingly little evidence to support this view other than the 1988 swarm. I present the most comprehensive phylogenetic study that suggests that the desert locust originated from the New World, contrary to the accepted view. I also present a hypothesis about how the ancestral Schistocerca might have colonized the New World in the first place in light of phylogenetic relationships with other cyrtacanthacridine genera.
| S-EPMC1691763 | biostudies-literature
Project description:Tychoparthenogenesis, a form of asexual reproduction in which a small proportion of unfertilized eggs can hatch spontaneously, could be an intermediate evolutionary link in the transition from sexual to parthenogenetic reproduction. The lower fitness of tychoparthenogenetic offspring could be due to either developmental constraints or to inbreeding depression in more homozygous individuals. We tested the hypothesis that in populations where inbreeding depression has been purged, tychoparthenogenesis may be less costly. To assess this hypothesis, we compared the impact of inbreeding and parthenogenetic treatments on eight life-history traits (five measuring inbreeding depression and three measuring inbreeding avoidance) in four laboratory populations of the desert locust, Schistocerca gregaria, with contrasted demographic histories. Overall, we found no clear relationship between the population history (illustrated by the levels of genetic diversity or inbreeding) and inbreeding depression, or between inbreeding depression and parthenogenetic capacity. First, there was a general lack of inbreeding depression in every population, except in two populations for two traits. This pattern could not be explained by the purging of inbreeding load in the studied populations. Second, we observed large differences between populations in their capacity to reproduce through tychoparthenogenesis. Only the oldest laboratory population successfully produced parthenogenetic offspring. However, the level of inbreeding depression did not explain the differences in parthenogenetic success between all studied populations. Differences in development constraints may arise driven by random and selective processes between populations.
| S-EPMC5551105 | biostudies-literature
Project description:Whereas short neuropeptide F (sNPF) has already been reported to stimulate feeding behaviour in a variety of insect species, the opposite effect was observed in the desert locust. In the present study, we cloned a G protein-coupled receptor (GPCR) cDNA from the desert locust, Schistocerca gregaria. Cell-based functional analysis of this receptor indicated that it is activated by both known isoforms of Schgr-sNPF in a concentration dependent manner, with EC(50) values in the nanomolar range. This Schgr-sNPF receptor constitutes the first functionally characterized peptide GPCR in locusts. The in vivo effects of the sNPF signalling pathway on the regulation of feeding in locusts were further studied by knocking down the newly identified Schgr-sNPF receptor by means of RNA interference, as well as by means of peptide injection studies. While injection of sNPF caused an inhibitory effect on food uptake in the desert locust, knocking down the corresponding peptide receptor resulted in an increase of total food uptake when compared to control animals. This is the first comprehensive study in which a clearly negative correlation is described between the sNPF signalling pathway and feeding, prompting a reconsideration of the diverse roles of sNPFs in the physiology of insects.
| S-EPMC3537624 | biostudies-literature