scholarly journals RNAi-Mediated Knockdown of Transcription Factor E93 in Nymphs of the Desert Locust (Schistocerca gregaria) Inhibits Adult Morphogenesis and Results in Supernumerary Juvenile Stages

2020 ◽  
Vol 21 (20) ◽  
pp. 7518
Author(s):  
Marijke Gijbels ◽  
Elisabeth Marchal ◽  
Thomas Wolf Verdonckt ◽  
Evert Bruyninckx ◽  
Jozef Vanden Broeck
Keyword(s):  
Schistocerca Gregaria ◽  
Fat Body ◽  
Total Duration ◽  
Early Response ◽  
Postembryonic Development ◽  
Early Gene ◽  
Pest Species ◽  
Desert Locust ◽  
Altered Expression ◽  
Transcript Levels

Postembryonic development of insects is coordinated by juvenile hormone (JH) together with ecdysteroids. Whereas the JH early response gene krüppel-homolog 1 (Kr-h1) plays a crucial role in the maintenance of juvenile characteristics during consecutive larval stages, the ecdysteroid-inducible early gene E93 appears to be a key factor promoting metamorphosis and adult morphogenesis. Here, we report on the developmental and molecular consequences of an RNAi-mediated knockdown of SgE93 in the desert locust, Schistocerca gregaria, a hemimetabolan species. Our experimental data show that injection of gregarious locust nymphs with a double-stranded RNA construct targeting the SgE93 transcript inhibited the process of metamorphosis and instead led to supernumerary nymphal stages. These supernumerary nymphal instars still displayed juvenile morphological features, such as a nymphal color scheme and body shape, while they reached the physical body size of the adult locusts, or even surpassed it after the next supernumerary molt. Interestingly, when compared to control locusts, the total duration of the fifth and normally final nymphal (N5) stage was shorter than normal. This appeared to correspond with temporal and quantitative changes in hemolymph ecdysteroid levels, as well as with altered expression of the rate-limiting Halloween gene, Spook (SgSpo). In addition, the levels of the ecdysone receptor (SgEcR) and retinoïd X receptor (SgRXR) transcripts were altered, indicating that silencing SgE93 affects both ecdysteroid synthesis and signaling. Upon knockdown of SgE93, a very potent upregulation of the SgKr-h1 transcript levels was observed in both head and fat body, while no significant changes were detected in the transcript levels of SgJHAMT and SgCYP15A1, the enzymes that catalyze the two final steps in JH biosynthesis. Moreover, the process of molting was disturbed in these supernumerary nymphs. While attempting ecdysis to the next stage, 50% of the N6 and all N7 nymphal instars eventually died. S. gregaria is a very harmful, swarm-forming pest species that destroys crops and threatens food security in many of the world’s poorest countries. We believe that a better knowledge of the mechanisms of postembryonic development may contribute to the discovery of novel, more selective and sustainable strategies for controlling gregarious locust populations. In this context, identification of molecular target candidates that are capable of significantly reducing the fitness of this devastating swarming pest will be of crucial importance.

scholarly journals The mechanism of C-20 hydroxylation of α-ecdysone in the desert locust, Schistocerca gregaria

1977 ◽  
Vol 168 (3) ◽  
pp. 513-520 ◽  
Author(s):  
P Johnson ◽  
H H Rees
Keyword(s):  
Schistocerca Gregaria ◽  
Fat Body ◽  
Difference Spectrum ◽  
Maximum Activity ◽  
Malpighian Tubules ◽  
Desert Locust ◽  
Ph Optimum ◽  
Developmental Variation ◽  
Moulting Hormone ◽  
Cytochrome P 450

1. The C-20 hydroxylation of alpha-ecdysone to produce beta-ecdysone was investigated in the desert locust, Schistocerca gregaria. 2. alpha-Ecdysone C-20 hydroxylase activity was located primarily in the fat-body and Malpighian tubules. The properties of the hydroxylation system from Malpighian tubules investigated further. 3. The enzyme system was mitochondrial, had a pH optimum of 6.5, an apparent Km of 12.5 micron and required O2 and NADPH. 4. The activity of the hydroxylation system showed developmental variation within the fifth instar, the maximum activity corresponding to the maximum tire of endogenous moulting hormone. The significance of these results is assessed in relation to the control of the endogenous titre of beta-ecdysone. 5. The mechanism of the hydroxylation system was investigated by using known inhibitors of hydroxylation reactions such as CO, metyrapone and cyanide. 6. The CO difference spectrum of the reduced mitochondrial preparation indicated the presence of cytochrome P-450 in the preparation. 7. It concluded that the alpha-ecdysone C-20 hydroxylase system is a cytochrome P-450-deendent mono-oxygenase.

scholarly journals Variation and structure of the eyes in the desert locust, Schistocerca gregaria (Forskål)

1947 ◽  
Vol 134 (875) ◽  
pp. 245-272 ◽  
Keyword(s):  
Schistocerca Gregaria ◽  
Postembryonic Development ◽  
Compound Eyes ◽  
Brown Pigment ◽  
Desert Locust ◽  
Direct Sunlight ◽  
The Third ◽  
Third Stage ◽  
Visual Impact ◽  
The One

The compound eyes of the solitaria phase individuals of the desert locust, Schistocerca gregaria (Forskål), are vertically striped with mostly 6 and 7, rarely 5 and 8, dark brown stripes, and a number of cream-coloured interstripes. In phase gregaria the interstripes, which are more or less invaded by brown pigment, are partially or wholely masked, the eye in the latter case presenting an almost uniformly dark brown appearance. The postembryonic development of the striped eyes, is described stage by stage. There is no stripe at the time of hatching. In the 6-striped eye one stripe is developed in the first-stage hopper and, subsequently a stripe is added at each of the five moults. In the 7-striped eye the one-moult-one stripe relationship holds good in most stages, but the extra seventh stripe is produced in two ways: (i) By the addition of two stripes at the second moult (i. e. the third-stage hopper has four stripes instead of three); and (ii) by the interposition of an extra-moult, usually in the third stage and rarely in the fourth, during which a new stripe is added (stripe-positive extra-moult). But extra-moulting does not necessarily lead to the addition of a stripe; stripe-neutral extra-moults are not infrequent. The development of the dorsal spot and the subdorsal streak are described. The mechanism of growth and the homology and nomenclature of the stripes and interstripes are discussed. The structure of the compound eyes and the pigmentary basis of stripe formation are described, and their effects on vision in solitaria and gregaria individuals discussed. Vision is discussed on the basis of ommatidial structure and pigmentation. In gregaria eyes a perfect apposition image is formed, the image being sharply defined. An ‘anti-halation’ device, produced by the post-retinular layer of pigment, is present. The eye is suited for diurnal vision, and strong direct sunlight is not avoided. In solitaria eyes the image is of the apposition type in its mode of formation but of the superposition type in effect; it has been termed a ‘pseudo-superposition’ image, and is more diffuse but brighter than in gregaria eyes. The ‘anti-halation’ device is weak and ineffective. The eye is suited for vision in subdued light and perceives movements rather than sharp images. Solitaria individuals, especially hoppers, avoid strong, direct sunlight. The effects of these differences in vision on the behaviour of gregaria - and solitaria -phase individuals are as follows: the former, owing to mutual visual impact induced by the formation of sharp images, tend to be gregarious; and further, owing to the presence of light-absorbing mechanisms, they do not avoid strong sunlight; the latter, on the other hand, owing to the want or comparative ineffectiveness of the above-mentioned features, neither tend to congregate nor to go out boldly into the bright open.

Some effects of the nematode Mermis nigrescens upon carbohydrate metabolism in the fat body of its host, the desert locust Schistocerca gregaria

1971 ◽  
Vol 49 (4) ◽  
pp. 431-434 ◽  
Author(s):  
Roger Gordon ◽  
John M. Webster ◽  
David E. Mead
Keyword(s):  
Carbohydrate Metabolism ◽  
Glycogen Phosphorylase ◽  
Schistocerca Gregaria ◽  
Fat Body ◽  
Constant Level ◽  
Desert Locust ◽  
Carbohydrate Levels ◽  
Fat Bodies

Adult desert locusts were experimentally infected with 50 Mermis nigrescens ova and changes in the fat body carbohydrate levels and glycogen phosphorylase activities recorded. At both 2 and 3 weeks after infection, the parasitism caused a significant reduction in the level of glycogen and non-glycogen carbohydrates in the host fat body, together with a progressive depletion of active and inactive glycogen phosphorylases. By feeding extensively upon the blood carbohydrates of the host, the developing nematode deprives the fat body of carbohydrates and thereby effects a reduction in glycogenesis by the host fat body. Increased catabolism (and (or) decreased anabolism) of the fat body phosphorylases, together with a possible suppression of the host "hyperglycaemic factor" by the nematode, prevent further glycogenolysis by the fat bodies of mermithid-infected locusts and allow a low, constant level of fat body glycogen to be maintained in these insects.

Inhibition of molting of the desert locust, Schistocerca gregaria, by the nematode parasite Mermis nigrescens

1974 ◽  
Vol 52 (12) ◽  
pp. 1535-1539 ◽  
Author(s):  
S. M. Craig ◽  
J. M. Webster
Keyword(s):  
Protein Synthesis ◽  
Schistocerca Gregaria ◽  
Fat Body ◽  
Nematode Parasite ◽  
Desert Locust ◽  
Body Protein

The older the host (Schistocerca gregaria) at infection, the greater the burden of parasitic Mermis nigrescens required to inhibit the next-but-one molt. Mermithid parasitism caused no change in ecdysone level in the host, but did cause a decrease in fat body protein synthesis. The effect of this decrease on host molting is discussed.

scholarly journals Purification and characterization of an insulin-related peptide in the desert locust, Schistocerca gregaria: immunolocalization, cDNA cloning, transcript profiling and interaction with neuroparsin

2008 ◽  
Vol 40 (3) ◽  
pp. 137-150 ◽  
Author(s):  
Liesbeth Badisco ◽  
Ilse Claeys ◽  
Matthias Van Hiel ◽  
Elke Clynen ◽  
Jurgen Huybrechts ◽  
...  
Keyword(s):  
Schistocerca Gregaria ◽  
Fat Body ◽  
Sequence Similarity ◽  
Desert Locust ◽  
Adult Males ◽  
Igf Binding Proteins ◽  
Insulin Superfamily ◽  
Related Peptide

Members of the insulin superfamily are not restricted to vertebrates, but have also been identified in invertebrate species. In the current report, we present the characterization of Scg-insulin-related peptide (IRP), an insulin-related peptide in the desert locust, Schistocerca gregaria. This peptide was isolated from corpora cardiaca (CC) extracts by means of a high-performance liquid chromatography (HPLC)-based purification strategy. Subsequent cloning and sequencing of the corresponding cDNA revealed that the encoded Scg-IRP precursor displays the structural organization that is typical for members of the insulin superfamily. Moreover, immunocytochemistry on brain tissue sections demonstrated the presence of Scg-IRP in median neurosecretory cells of the pars intercerebralis and their projections towards the storage part of the CC. Quantitative real-time RT-PCR studies revealed the presence of Scg-IRP transcripts in a variety of tissues, including nervous tissue and fat body. Furthermore, these transcripts showed a tissue- and phase-dependent, temporal regulation during the reproductive cycle of adult males and females. Finally, we demonstrated that Scg-IRP interacts in vitro with a recombinant neuroparsin, a locust protein displaying sequence similarity with vertebrate IGF binding proteins.

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