Vitellogenesis in insects and other groups: a review

Abstract

The eggs from oviparous organisms contain large amounts of vitellus, or yolk, which are utilized by the growing embryo. Vitellogenesis is the process of vitellus accumulation and involves massive heterosynthetic synthesis of the protein vitellogenin (Vg) and its deposition in the oocyte. This work summarizes data on Vg structure, synthesis, uptake by oocytes and its fate during embryogenesis. The hormonal control of vitellogenesis and its tissue, sex and temporal regulation are also discussed. Where it is available, data on structure and expression of Vg-coding genes are reviewed. Insect vitellogenesis is priorized although other oviparous animal groups outside insects are also treated.

Calcium-regulated fusion of yolk granules is important for yolk degradation during early embryogenesis of Rhodnius prolixusStahl

“…Activation of these enzymes is achieved by luminal acidification of YGs, a process that is mediated by proton pumps (Fagotto, 1991;Nordin et al, 1991;Mallya et al, 1992;Fagotto, 1995). VT and hydrolases, such as cathepsin B and carboxypeptidase, are known to accumulate in the oocytes during oogenesis and to be stored in YGs (Wall and Meleka, 1985;Oliveira et al, 1986;Raikhel and Dadhialla, 1992;Valle, 1993;Sappington and Raikhel, 1998;Cho et al, 1991;Cho et al, 1999;Liu and Nordin, 1998;Yin et al, 2001). Newly laid eggs are therefore able to initiate VT degradation.…”

“…Endocytic activities during insect oogenesis involve the incorporation of the lipophosphoglycoprotein vitellogenin (Oliveira et al, 1986;Raikhel and Dadhialla, 1992;Valle, 1993;Sappington and Raikhel, 1998). Once inside the oocyte the vitellogenin, now referred to as vitellin (VT), is stored in organelles known as yolk granules (YGs) (Kunkel and Nordin, 1985;Purcell et al, 1988;Machado et al, 1998).…”

Effect of ivermectin on the life cycle and larval fat body of Culex quinquefasciatus

“…The vitellin is the major protein of yolk being produced from another protein, the vitellogenin (VG). The synthesis of VG occurs in a short period of time, involving extensive cytological changes of the fat body and ovaries (Valle, 1993). Clements (1996) have pointed out that some increase in cellular size occurs with the accumulation of lipids and glycogen, while the storage of proteins is associated with a considerable increase in the volume of the fat body cells.…”

Oocyte development in Melanogryllus desertus (Pallas, 1771) (Orthoptera: Gryllidae): presence of Balbiani body*

“…Vitellogenesis is an important process for the maturation of an insect egg. In this period, rapid oocyte growth occurs due to yolk deposition (Valle, 1993). Vitellogenins, which are a group of proteins synthesized outside the ovary, are the main component of the yolk and stored as vitellin in oocytes (Hagedorn and Kunkel, 1979).…”