ABSTRACT
R ik V an A ntwerpen1, D aphne Q.-D. P ham2 and R olf Z iegler3 xDepartment o f Biochemistry, Virginia Commonwealth University, Richmond,
Virginia 23298, USA hgvanant@hsc. vcu. edu
2Department o f Biological Sciences, University o f Wisconsin - Parkside, Kenosha, Wisconsin 53141, USA
3Institute o f Zoology, Martin Luther University, 06099 Halle, Germany
I. INTRODUCTION
The development of an insect embryo requires a continuous supply of protein and lipid nutrients. Large amounts of these nutrients are stored in the insect egg for later consumption. The accumulation of protein reserves by the insect oocyte is well documented (Raikhel and Dhadialla, 1992; Sappington and Raikhel, 1998). Developing oocytes take up various proteins from the haemolymph by receptormediated endocytosis, and upon entering the oocyte, these proteins are stored undigested in cytoplasmic yolk bodies. The most prominent protein accumulating this way is vitellogenin (Vg), which provides the bulk of amino acids needed for embryonic growth. The Vgs of many insect species have been characterized, and cDNAs of several Vgs have been cloned (Sappington and Raikhel, 1998). In addition, cDNAs for the Vg-receptor of the yellow fever mosquito, Aedes aegypti (Sappington et a l , 1996), and for the yolk protein receptor of the fruit fly, Drosophila melanogaster (Schonbaum et al., 1995, 2000), have been cloned. While these results have firmly established the insect oocyte as a model system for receptor-mediated endocytosis, much less information is available on the accumulation and storage of lipid nutrients by the developing oocyte.
