Vitellogenesis in Dipetalogaster maxima, a vector of Chagas´ disease.

AGUIRRE, SA; GARCIA, L; FREDE, S; SOSA, LUARA; CANAVOSO, LE; RUBIOLO, ER

Tcson, Arizona, USA.

Simposio; Fifth International Symposium on Molecular Insect Science; 2006

Center for Instect Science-University of Arizona

Vitellogenesis in Dipetalogaster maxima, a vector of Chagas’ disease (Hemiptera:Reduviidae).   S.A. Aguirre, L. Garcia, S. Frede, L. Sosa, L.E. Canavoso and E.R. Rubiolo. Departamento de Bioquímica Clínica, CIBICI-Conicet. Facultad de Ciencias Químicas, Universidad Nacional de Córdoba. Córdoba, Argentina. CP 5000.   Hematophagous insects, like vectors of Chagas’ disease, must surpass a threshold level in terms of the amount and quality of the blood meal in order to successfully to produce eggs. During this process, the fat body synthesizes the main egg protein, vitellogenin (Vg), which will be taken up by the ovary to be stored as vitellin (Vt). Vg and Vt have been isolated from several species and their levels are indicative of the efficiency of the oogenesis process. However, information about their dynamics and regulation in Chagas’ disease vectors is still scarce. In this work, therefore, we have analyzed in anautogenous and autogenous females of Dipetalogaster maxima: a] the kinetic of Vg synthesis in fat body, b] Vg  levels in hemolymph, and c] the stores of Vt in ovary. Vg synthesis and its levels in hemolymph were achieved by western-blot and enzyme-linked-immunoassay (ELISA), respectively. The stores of Vt in ovary was analyzed by immunohistochemistry.  In anautogenous insects the study was performed between 2-8 days post-ecdysis and between 2- 20 days post-blood feeding.  In addition, autogenous females were studied between 2-15 days post-ecdysis.  During the period post-ecdysis anautogenous D. maxima showed decreased synthesis of Vg and concomitantly, low levels of Vg in hemolymph (5.5x10-3 µg/µl at day 4). After a blood meal, Vg synthesis in fat body and its levels in hemolymph increased significantly, reaching at day 20 post-feeding approximately 19 µg/µl. Histological and immunohistochemical studies of the ovaries were in agreement with the biochemical findings, especially the development of the tissue from day 2 post-blood feeding as well as the accumulation of Vt in developing oocytes.   Autogenous insects displayed a pattern for Vg and Vt quite different compared with anautogenous females, characterized by a decreased Vg synthesis and a poor development of the ovary.   The levels of Vg in hemolymph during the period post-ecdysis fluctuated between 1.5- 4.0x10-3 µg/µl. This was sufficient however to produce at least one batch of eggs. Supported by Secyt-UNC (E.R.R) and CONICET-Argentina (L.E.C).