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Identifier 000410328
Title Molecular characterization of temephos resistance in the major dengue and chikungunya vector Ae.albopictus
Alternative Title Μοριακός χαρακτηρισμός της ανθεκτικότητας του κουνουπιού Ae.albopictus, φορέα του δάγκειου πυρετού και του ιού chikungunya, στο οργανοφωσφορικό εντομοκτόνο τέμεφος
Author Γρηγοράκη, Λίντα
Thesis advisor Χαλεπάκης, Γεώργιος
Reviewer Βόντας, Ιωάννης
Weill, Mylene
Καλαντίδης, Κρίτων
Αλεξανδράκη, Δέσποινα
Λαδουκάκης, Εμμανουήλ
Siden-Kiamos, Inga
Abstract Diseases transmitted by mosquitoes, like malaria, dengue, zika, yellow fever e.t.c are a major cause of human suffering resulting every year in mortality and morbidity at a global scale with a large socio-economical impact. The main way to prevent these diseases is to control the population size of mosquitoes and the most efficient and widely used method for that remains the use of insecticides. However, insecticide resistance is being selected in mosquito populations threatening the efficiency of insecticide based interventions. As a limited number of different insecticide classes are available it is highly important to design efficient insecticide resistant management strategies to overcome this major problem. A prerequisite for that is to understand the molecular mechanisms conferring resistance in order to make evidence based decisions. In this PhD we have investigated the molecular mechanisms conferring resistance against the organophosphate larvicide temephos in Ae. albopictus, one of the most invasive species found worldwide and a major vector of arboviral diseases like dengue and chikungunya. Increased esterase activity was associated with the resistance phenotype and a new generation sequencing analysis revealed the up-regulation of several detoxification enzymes in the resistant strain, with the two esterases CCEae3a and CCEae6a being among the most prominent. The genes of these two esterases were also found to be amplified in the resistant strain, explaining at least partially their transcriptional up-regulation and their amplification was further linked to the resistance phenotype through genetic crosses. Subsequently CCEae3a from Ae.albopictus and Ae.aegypti (CCEae3a was associated with temephos resistance also in this vector) was expressed using the baculovirus expression system and used to characterize its interaction with temephos-oxon, the toxic form of the insecticide. The kinetic constants of their interaction were estimated showing a high binding affinity of CCEae3a for temephos-oxon accompanied by a very slow hydrolysis rate, which is characteristic for the sequestration resistance mechanism. The tissue localization of CCEae3a was also investigated in Ae.albopictus larvae through western blots and immunochistochemistry experiments, showing its localization in malpigian tubules and the nerve cord, the target tissue of organophosphate insecticides. Finally the geographical distribution and evolutionary origin of the amplified esterase locus was investigated in individuals collected from 16 different countries. Amplification of both esterases was found in collections from Greece and Florida (U.S.A) representing a single amplification event that has spread between the two countries through passive transportation of this disease vector. A second and independent amplification event involving amplification of CCEae3a only was also detected in individuals from Florida.
Language Greek, English
Subject Biochemical analysis
Gene amplification
Geographical distrifution
Βιοχημική ανάλυση
Γεωγραφική εξάπλωση
Γονιδιακός πολλαπλασιαμός
Issue date 2017-07-13
Collection   Faculty/Department--Faculty of Sciences and Engineering--Department of Biology--Doctoral theses
  Type of Work--Doctoral theses
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