The storage of nutritional resources during vitellogenesis of Panstrongylus megistus (Hemiptera: Reduviidae): The pathways of lipophorin in lipid delivery to developing oocytes

FRUTTERO, LL; FREDE, S; RUBIOLO, ER; CANAVOSO, LE

JOURNAL OF INSECT PHYSIOLOGY

PERGAMON-ELSEVIER SCIENCE LTD

Año: 2011 vol. 57 p. 475 - 486

0022-1910

In this work, we have analyzed the pathways by which lipophorin (Lp) delivers its lipid cargo to developing oocytes of <span style="font-style: italic;">Panstrongylus megistus</span>,   a hematophagous vector of Chagas’ disease. Lp, vitellin, total lipids   and proteins were measured in ovarian tissues at different stages of the   reproductive cycle. Localization of Lp in developing oocytes, mainly at   their cortical area, was demonstrated by immunofluorescence assays   using an anti-Lp antibody labeled with FITC. <span style="font-style: italic;">In vivo</span>   approaches injecting fluorescently labeled Lp to follow the course of   the entire particle (Lp-DiI or Lp-Oregon Green) or its lipid cargo   (Lp-Bodipy-FA) were monitored by laser scanning confocal microscopy.   Significant increases in the amounts of lipids, proteins and vitellin   were observed in ovarian tissue with the progress of vitellogenesis.   Unexpectedly, an increase in the amount of Lp was also observed. The   experiments <span style="font-style: italic;">in vivo</span>   demonstrated that the uptake of fluorescent Lp labeled on its protein or   lipid moiety by developing oocytes occurred very fast, being impaired   at low temperatures. The co-injection of fluorescent Lp and vitellogenin   (Vg) showed that both particles co-localized inside yolk bodies,   confirming the endocytic pathway for Lp. When the fate of lipids   transferred to oocytes was evaluated in vitellogenic females by   co-injecting Lp-Bodipy-FA and Lp-DiI, the signal for Bodipy-FA was found   in both lipid droplets and yolk bodies. In contrast, in injected   females kept at 4 °C the fluorescence was reduced, being observed   exclusively in lipid droplets, implying that lipid transfer to the   oocyte was diminished but not abolished. Taken together, the results   demonstrate that in the hematophagous <span style="font-style: italic;">P. megistus</span>,   the storage of lipid resources by developing oocytes occurs by the   convergence of different pathways by which Lp maximizes the delivery of   its lipid cargo. In addition, it was also shown that, to some extent,   lipids stored in the oocyte lipid droplets can also originate from   endocytosed Vg. The relevance of these events in the context of the   physiology of reproduction in <span style="font-style: italic;">P. megistus</span> is discussed.