<p>Kukuruzni plamenca (<em>Ostrinia nubilalis</em>, Hbn.) je vrsta umerenog klimatskog područja <br />koja niske zimske temperature preživljava ulaskom u dijapauzu u stadijumu gusenice. Dijapauza i otpornost na hladnoću (cold hardiness, eng.), kod mnogih insekatskih vrsta često predstavljaju esencijalne, tesno povezane komponente strategije preživljavanja delovanja niske temperature, kao što je to slučaj i kod kukuruznog plamenca <em>Ostrinia nubilalis</em>, Hbn. U okviru grupe insekata otpornih na hladnoću, svrstava se u insekte otporne na zamrzavanje (freeze tolerant, eng.) jer su sposobne da prežive ekstracelularno zamrzavanje telesnih tečnosti.</p><p>Iako se o osnovnim strukturnim i metaboličkim dešavanjima u dijapauzi insekata već dosta zna, još uvek postoje brojne dileme o ovom vidu preživljavanja insekata u nepovoljnim uslovima sredine, posebno sa aspekta izloženosti niskim zimskim temperaturama i mehanizmima krioprotekcije. Zbog toga je cilj ove doktorske disertacije bio da se sa aspekta biofizičkih osobina lipida i sastava masnih kiselina: odrede biofizičke osobine (temperature faznog prelaza) ukupnih lipida nedijapauzirajućih i dijapauzirajućih gusenica tokom dijapauze (početak, sredina i kraj), kao i u kontrolisanim uslovima hlađenja dijapauzirajućih gusenica; zatim da se odredi zastupljenost pojedinih klasa lipida u hemolimfi i masnom telu nedijapauzirajućih i dijapauzirajućih gusenica; da se utvrde promene sastava masnih kiselina strukturne (polarne) i rezervne (nepolarne) frakcije lipida celih gusenica tokom dijapauze i pod uticajem različitih temperatura u eksperimentalnim uslovima; kao i da se odredi tkivna specifičnost, hemolimfe i masnog tela, masnih kiselina ukupnih lipida i biofizičke osobine ukupnih lipida masnog tela nedijapauzirajućih i dijapauzirajućih gusenica tokom dijapauze, kao i u kontrolisanim uslovima hlađenja dijapauzirajućih gusenica. </p><p>U analizi lipida kukuruznog plamenca <em>Ostrinia nubilalis</em>, Hbn. korišćene su sledeće tehnike: tankoslojna hromatografija (TLC) sa skenirajućom denzitometrijom, za razdvajanje i analizu klasa lipida; zatim gasno-masena hromatografija (GC-MS), za analizu masnih kiselina kao i diferencijalna skenirajuća kalorimetrija (DSC – differential scanning calorimetry, eng.), za termalnu analizu ekstrahovanih lipida.</p><p>Kod gusenica <em>Ostrinia nubilalis</em> sastav masnih kiselina ukupnih lipida analiziranih tkiva i lipidnih frakcija značajno se razlikuje između ova dva fiziološka stanja, stanja dijapauze i nedijapauze. Dijapauza indukuje značajno povećanje sadržaja mononezasićenih masnih kiselina, pre svega palmitoleinske (16:1n-7) i oleinske masne kiseline (18:1n-9) uz istovremeno smanjenje sadržaja zasićenih i polinezasićenih masnih kiselina, pre svega palmitinske (16:0) i linolne masne kiseline (18:2n-6). Temperature faznog prelaza ukupnih lipida celih gusenica i masnog tela značajno su niže kod dijapauzirajućih gusenica <em>O. nubilalis</em>, usled značajnog povećanja stepena nezasićenosti masnih kiselina u njihovom sastavu. Značajno niže temperature faznog prelaza lipida dijapauzirajućih gusenica <em>O.<br />nubilalis</em> rezultat su povećanja stepena nezasićenosti njihovih masnih kiselina. Možemo zaključiti da su promene u sastavu masnih kiselina lipida indukovane dijapauzom važna komponenta preživljavanja niskih temperatura kod <em>O. nubilalis</em> Hbn. jer se veliki deo lipida održava u tečnom stanju čak i na temperaturama daleko ispod 0°C, što je neophodno za održavanje njihove fluidnosti odnosno funkcionalnosti.</p> / <p>European corn borer (<em>Ostrinia nubilalis</em>, Hbn.) inhabiting temperate regions that survive low winter temperatures as a diapausing fifth instar larva. Diapausing larvae are cold hardy and freeze tolerant as they are able to survive the extracellular formation of ice crystals. Winter survival for many insect species living in seasonally cold environments includes a radical remodeling of metabolism. This implies entry into a developmentally arrested, hypometabolic state of winter diapause, which in <em>O. nubilalis</em> and many other insect species of these habitats is closely related to their cold hardiness.</p><p>Although the basic structural and metabolic events consider insect diapause is already known, there are still many doubts about the survival of insects in an unfavorable environment, particularly in terms of exposure to low winter temperatures and mechanisms of cryoprotection. Therefore, the aim of this thesis in terms of biophysical properties of lipids and fatty acid compositions, was to: i) to determine the biophysical properties (phase transition temperatures) of the total lipids of non-diapausing larvae and diapausing larvae during diapause (early diapause, mid diapause and termination of diapause), as well as under controlled cooling conditions during different phases of diapause; ii) to determine the fatty acid compositions of structural (polar) and storage (non-polar) total lipid fractions of non-diapausing larvae and diapausing larvae, as well as under the influence of different <br />temperatures during diapause in the controled experimental conditions; iii) to determine the lipid classes composition of total lipids extracted from the haemolymph and fat body of non-diapausing and diapausing larvae; iiii) to determine the haemolymph and fat body total lipid fatty acid compositions as well as the biophysical properties of the fat body total lipids of non-diapausing larvae and diapausing larvae during diapause as well as in terms of controlled cooling conditions. Thus, our research was focused on the non-diapausing (ND) as well as the diapausing larvae (D) that were exposed to low temperatures during different phases of diapause.</p><p>During analysis of European corn borer <em>O. nubilalis</em> lipids, the following techniques was used: thin layer chromatography (TLC) with scanning densitometry, for the separation and quantification of lipid classes; gas-mass chromatography (GC-MS ) for the analysis of the fatty acid composition of lipids and the differential scanning calorimetry (DSC), for the thermal analysis of the extracted lipids.</p><p>The fatty acid compositions and biophysical properties of lipids differed markedly between non-diapausing and diapausing larvae of <em>O. nubilalis</em>. Diapause was associated with a dramatic increase mainly the proportions of palmitoleic acid (16:1n-7) and oleic acid (18:1n-9), with concurrent reductions in palmitic acid (16:0) and linoleic acid (18:2n-6). The increase in the level of unsaturation of lipids, which caused a marked shift in their phase transitions to lower temperatures, was triggered by diapause rather than low temperatures. Adjustments of fatty acid compositions are likely to be an important component of winter diapause mechaisms, possibly maintaining the fluidity of cell membranes, and the functionality of the organism during lower winter temperatures. We conclude that <em>O. nubilalis </em>undergoes remodeling of fatty acid profiles of lipids as an element of its overwintering physiology which may improve the ability to harden during diapause.</p>
| Identifer | oai:union.ndltd.org:uns.ac.rs/oai:CRISUNS:(BISIS)87272 |
| Date | 24 July 2014 |
| Creators | Vukašinović Elvira |
| Contributors | Grubor-Lajšić Gordana, Šimić Smiljka, Blagojević Duško, Kojić Danijela |
| Publisher | Univerzitet u Novom Sadu, Prirodno-matematički fakultet u Novom Sadu, University of Novi Sad, Faculty of Sciences at Novi Sad |
| Source Sets | University of Novi Sad |
| Language | Serbian |
| Detected Language | English |
| Type | PhD thesis |
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