Neuropeptides controlling food uptake and reproduction in the desert locust Schistocerca gregaria

Abstract

Normal 0 21 false false false NL-BE X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:Standaardtabel; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"TimesNew Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;}For thousands ofyears, desert locusts (Schistocercagregaria Forskål) have been threatening the agriculturalproduction in large parts of Northern Africa, the Middle-East and the Indiansubcontinent. Usually, these animals occur at low population densities andbehave as loners that are relatively harmless. Under favorable environmentalconditions (higher food availability), the desert locusts will reproducemassively. Because of the resulting increase in population density, theseanimals will undergo physiological and morphological changes, as well asbehavioral changes causing the locusts to actively aggregate. This process caneventually lead to the formation of enormous swarms of billions of locusts thatcan inflict major damage, both to the natural vegetation and agriculturalcrops. Influencing locust reproduction and food intake might be a suitablestrategy for preventing locust outbreaks. Unfortunately, our knowledge onlocust physiology is still very limited and additional research is needed tofully understand the relevant physiological processes. In the context of this PhD thesis, the involvement of the neuropeptidesCRF-related diuretic hormone (CRF/DH), neuropeptide F (NPF) and ovarymaturating parsin (OMP) was analyzed in the regulation of reproduction and foodintake in the desert locust. By cloning twoprepropeptide cDNAs, we were able to demonstrate that in S. gregaria OMP and CRF/DH originate from the same precursorproteins. Interestingly, the currently known CRF/DH precursors from otherinsect species do not code for OMP-like molecules. As previously suggested, OMPseems to occur only in a limited number of taxa, although its exact taxonomicoccurrence has not been determined yet. By performing feeding experiments, wewere able to confirm that CRF/DH negatively regulates food intake in locusts,as was previously suggested. Moreover, we demonstrated that CRF/DH alsonegatively affects oocyte growth and ecdysteroid levels in the hemolymph andovaries of adult female S. gregaria.No effects of CRF/DH on insect reproductive physiology were previouslyreported.In the second part ofour research, we identified a NPF-prepropeptide sequence based on sequenceinformation from the S. gregariaEST-database. Analysis of this precursor sequence demonstrated that apreviously purified NPF-like peptide of S.gregaria is actually a C-terminal fragment of the (based on the precursorsequence) predicted long NPF peptide. This naturally occurring shorter formpreviously proved to be biologically active and was designated truncated NPF or trNPF to make the distinction with the predicted long NPF-peptide (that could not yet be demonstrated in locusts) andthe sNPF-peptide (that seems to be less related to NPF than its name suggests). We wereable to demonstrate that trNPF stimulates food intake in S. gregaria. Previously, this effect of NPF on food intake had onlybeen demonstrated in the fruit fly Drosophilamelanogaster, although indications were found for a similar role of NPF inother insect species. In accordance to the role of trNPF in the regulation offood intake, we observed that the levels of the S. gregaria NPF-precursor transcript are regulated in function ofthe animals feeding state. We were also able to demonstrate that trNPF has astimulatory effect on weight increase in S.gregaria. In addition to itspreviously described effect on female reproductive physiology, we were able to demonstratethat trNPF also influences male reproductive physiology in S. gregaria. By applying different physiological assays, weobserved effects of trNPF on sexual maturation, as well as on the reproductivesuccess of adult male S. gregaria.Only one previous report on D.melanogaster described the link between NPF and male reproduction.The results describedin this thesis shed a new light on the regulation of food intake andreproduction in the desert locust and provide new perspectives for thephysiological research in other insect species.<w:latentstyles deflockedstate="false" defunhidewhenused="true"  <w:lsdexception="" locked="false" priority="0" semihidden="false"  <w:latentstyles="" for="" thousands="" of="" years,="" desert="" locusts="" (schistocerca="" gregaria forskål)="" have="" been="" threatening="" the="" agricultural="" production="" in="" large="" parts="" northern="" africa,="" middle-east="" and="" indian="" subcontinent.="" usually,="" these="" animals="" occur="" at="" low="" population="" densities="" behave="" as="" loners="" that="" are="" relatively="" harmless.="" under="" favorable="" environmental="" conditions="" (higher="" food="" availability),="" will="" reproduce="" massively.="" because="" resulting="" increase="" density,="" undergo="" physiological="" morphological="" changes,="" well="" behavioral="" changes="" causing="" to="" actively="" aggregate.="" this="" process="" can="" eventually="" lead="" formation="" enormous="" swarms="" billions="" inflict="" major="" damage,="" both="" natural="" vegetation="" crops.="" influencing="" locust="" reproduction="" intake="" might="" be="" a="" suitable="" strategy="" preventing="" outbreaks.="" unfortunately,="" our="" knowledge="" on="" physiology="" is="" still="" very="" limited="" additional="" research="" needed="" fully="" understand="" relevant="" processes.="" context="" phd="" thesis,="" involvement="" neuropeptides="" crf-related="" diuretic="" hormone="" (crf="" dh),="" neuropeptide="" f="" (npf)="" ovary="" maturating="" parsin="" (omp)="" was="" analyzed="" regulation="" locust.by="" cloning="" two="" prepropeptide="" cdnas,="" we="" were="" able="" demonstrate="" in s.="" gregaria="" omp="" crf="" dh="" originate="" from="" same="" precursor="" proteins.="" interestingly,="" currently="" known="" precursors="" other="" insect="" species="" do="" not="" code="" omp-like="" molecules.="" previously="" suggested,="" seems="" only="" number="" taxa,="" although="" its="" exact="" taxonomic="" occurrence="" has="" determined="" yet.="" by="" performing="" feeding="" experiments,="" confirm="" negatively="" regulates="" locusts,as="" suggested.="" moreover,="" demonstrated="" also="" affects="" oocyte="" growth="" ecdysteroid="" levels="" hemolymph="" ovaries="" adult="" female="" s.="" gregaria.no="" effects="" reproductive="" reported.in="" second="" part="" research,="" identified="" npf-prepropeptide="" sequence="" based="" information="" est-database.="" analysis="" purified="" npf-like="" peptide="" gregaria is="" actually="" c-terminal="" fragment="" (based="" sequence)="" predicted="" long ="" npf="" peptide.="" naturally="" occurring="" shorter="" form="" proved="" biologically="" active="" designated="" truncated="" npf or="" trnpf ="" make="" distinction="" with="" npf-peptide="" (that="" could="" yet="" locusts)="" snpf-peptide="" less="" related="" than="" name="" suggests).="" trnpf="" stimulates="" gregaria.="" previously,="" effect="" had="" fruit="" fly="" drosophila="" melanogaster,="" indications="" found="" similar="" role="" species.="" accordance="" intake,="" observed="" the s.="" npf-precursor="" transcript="" regulated="" function="" animals ="" state.="" stimulatory="" weight="" gregaria. in="" addition="" described="" physiology,="" influences="" male="" applying="" different="" assays,="" sexual="" maturation,="" success="" gregaria.only="" one="" previous="" report="" d.="" melanogaster="" link="" between="" reproduction.the="" results="" thesis="" shed="" new="" light="" provide="" perspectives="" species.nrpages: 179status: publishe